Month: April 2023

State institutions, responsible for managing natural and socioeconomic disasters, can create favorable or adverse conditions for the recovery of the productive capacity of an agroecosystem. In this respect, there are institutions that favor the resilience of an agroecosystem more than others. In contrast to private or simply state property, communal forms of ownership, characteristic of traditional rural cultures, result in management approaches that adapt more easily to surprises or changes experienced by ecosystems.”This emphasis on institutions and the resilience dimension suggests stronger links between agroecology and fundamental environmental, ethical, political, and governance related questions and issues about the right and access to land and other natural resources and ecosystem services, such as water, soil, forests, and pollinators. It also underlines the importance of wider disciplinary and practical perspectives, such as landscape agroecology and the process of landscape planning in rural as well as linked rural–urban settings. Wezel and co-authors emphasize the relevance of working with “agroecology territories” in a more holistic framework combining sustainable agriculture and food systems as well as addressing biodiversity conservation, as places actively engaging in transition to sustainable farming and food systems.The agroecosystem concept and the science of agroecology provide a foundation for examining and understanding the interactions and relationships among the diverse components of the food system.There is a clear and undisputable link between how food is produced and how it goes into the food system. Stassart and co-authors emphasized ways in which agroecological systems could expand to a broader level,hydroponic grow system suggesting greater valorization of agrobiodiversity and the underlying diversity of knowledge found in both farming and food system, while providing broader perspectives of agroecology both in farming and food systems.

Logically, food cannot be claimed to be “sustainable,” even when being produced in a “sustainable way,” if it feeds into and contributes to food systems which are fundamentally unsustainable, for example, are contradicted by the use of huge amounts of fossil fuels or packaging material, or increase social inequity, or are wasteful of other tangible and intangible resources. Sustainability has multiple dimensions, and as emphasized by Gliessman : “A sustainable food system is one that recognizes the whole systems nature of food, feed and fiber production in balancing the multifaceted concerns of environmental soundness, social equity, and economic viability among all sectors of society, across all nations and generations.” Gliessman writes, with a background of 15 years of experience with an agroecology course, about the constraints of earlier framings of agroecology only as a science: “… they are primarily trying to make an argument that agroecology is basically a science for developing new food production technologies that do a lot of positive things for agriculture, the environment, and for people. This is good, but what they don’t seem to acknowledge is that agroecology is also a social movement with a strong grounding in the science of ecology. And when I say strong grounding in ecology, I mean grounded in our understanding of relationships, interactions, co-evolution, and a capacity to change to meet the complex aspects of the sustainability we are trying to achieve in food systems – from local to global.” Gliessman mentions five important elements of alternative food system : “In such a system food production and consumption has a bio-regional basis; the food supply chain has a minimum number of links; farmers, consumers, retailers, distributors, and other actors exist in the context of an interdependent community and have the opportunity for establishing real relationships; opportunities exist for the exchange of knowledge and information among all those who participate in the food system; and the benefits and burdens of the alternative food system are shared equally by all participants.

These aspects of an alternative food system are closely interrelated.” The linkages between agroecology and food sovereignty receive wide acknowledgement and detailed explanation by agroecological and food sovereignty movements , viewing agroecology as a major catalyst for enabling the realization of the agrarian reform called for by the food sovereignty movements. These movements focus upon principles of low-input use, resilience, sustainability as well as its prioritization of smallholders or peasant farmers . Food sovereignty and agroecology are also strongly united through their agency for and common defense of what are claimed as the common inheritances of humanity in terms of natural resources. Altieri and Nicholls demonstrate how different dimensions of sovereignty including food, energy, and technological sovereignties are all critical to agroecology and contribute to its resiliency. Table 1 suggests how linkages between key features of agroecology on a wider scale can be brought into important functions and structures of entire food systems. Multi-functionality and resilience are highlighted by numerous agroecological scholars and address agroecological systems’ capacities and aims . These scholars assess system properties such as ability to absorb shocks, and other inherent capacities to undergo relevant transformations, transitions, and processes of stabilization under changing and new conditions through feedback loops and iterative development processes . Resilience is a relevant key concept which potentially informs the design and maintenance of an agroecological food system, which can build upon local structures of markets, linking reciprocal flows, for example, between urban and rural landscapes, preserving food cultures and nourishment, and opening new possibilities for processing, storing, and retailing.This holistic understanding of health and the importance of maintaining a high-immunity level is also relevant for food systems, where the juxtaposition of feedback loops, like immune system response, are imagined to help regulate the resource flows and stimulate the social connectedness in the food system, and emphasize the nourishment aspect of the food which is produced, exchanged and eaten in the food system. Nourishment is an important characteristic, of food, produced under circumstances which nourish the soil and environment, but also within a food system which aims at composing our entire diets as a “sustainable diet,” as defined by FAO: “those diets with low environmental impacts which contribute to food and nutrition security and to healthy life for present and future generations.

Sustainable diets are protective and respectful of biodiversity and ecosystems, culturally acceptable, accessible, economically fair and affordable; nutritionally adequate, safe and healthy; while optimizing natural and human resources” . In addition to the established four aspects of food security , and in connection with the institutional framework and governance of food, the Ryerson University Centre for Studies in Food Security adds a fifth dimension of food security, namely “agency,” which multiple examples and cases point to as the most crucial critical factor for all aspects of food security , and which highlight equity as an important pillar of agroecological food systems. This also links to “nourishment” as a concept which goes far beyond “providing passive populations with calories,” focusing instead on peoples’ ability, access and right to grow, exchange, and eat healthy, nutritious food which is meaningful to them, in a fair and equitable way .Potentials in the agriculture and food systems that link urban and rural areas need to be maximized as a normal part of a balanced development process. City Region Food Systems is referred to as a cutting-edge concept . In this article,rolling benches we understand a city-region context for food systems as a landscape which includes rural, urban, and peri-urban areas, the two latter varying from a few thousand persons to many million people , which of course will call for widely different place-based and context relevant solutions. The increasing and partly unplanned urbanization has led to significant changes in diets, consumption patterns, and food trade , and in many urban areas, food markets are detached from local or domestic food production. In addition,huge amounts of so-called waste are produced, both in terms of food waste from processing and ensuring availability of a wide range of food at all times for eaters, as well as waste based on non-renewable resources . The fact that we talk about “waste” underlines the detachment from food production and farming, soil management, animal keeping, and resource cycles which were not present just 100 years ago These issues are addressed by the first two points in Table 1, which are strongly interlinked and enforce minimal external inputs and recycling of resources and biomass . In a city-region context, this clearly calls for a reorganization of resource cycles and avoidance of losses of energy, water, and nutrients in a combined rural–urban landscape. Where the linkages between rural and urban areas in some cases are facilitated by local governance systems in terms of markets linking, for example, smallholder farmers with urban markets , creation of full resource cycles including, for examples, compost material from cities to the soil and the rural areas, seem to be rarely addressed. Such cycles could involve human food waste being converted into animal feed and compost, energy in terms of bio-fuels produced from what normally would be considered as organic waste, minimization of plastic and packaging, and systems involving human urine and feces being composted and/or recycled in safe and responsible ways. Indeed, such agro-waste-recycling systems enabled Paris to rely on its local food shed for over 1,000 years . The system boundaries in a city-region food system cannot be clearly defined, and a “completely closed food system” would be unlikely, even a contextualized food system, shaped, and iteratively co-created by multiple involved actors, and based on recycling and closed loops principles. Referring to the four-dimensional sustainability concept including environmental, social, economic, and institutional levels, as described by Valentin and Spangenberg , Spangenberg and FAO , an agroecological food system in a city-region context will consist of a complex web of smaller food systems, for example, involving CSAs, urban, and peri-urban farming and a number of different supply chains and levels of organization, which interact and overlap internally as well as with surrounding landscapes and food systems.

Most likely, products from other geographic and climatic zones, for example, coffee and spices, will be involved, and inclusion of surrounding marine or other landscape elements further blur apparently clear systems boundaries. Furthermore, vulnerability to local shocks raises the general idea of crisis-preparedness and will always call for a certain ability of all food systems to step in and assist others, in case of failing harvests or natural disasters, and make wider connections between food systems desirable. Trade and transport between different food systems can be organized in ways which are equitable and environmentally not burdening, and can supplement local food systems rather than displace local produce. These aspects need to be considered if the aims and characteristics of agroecological food systems are to be taken seriously. Mendéz and co-authors discussed transformative agroecology and stated that agroecology is explicitly committed to a more just and sustainable future by reshaping power relations from farm to table. In our contextualization of agroecological food systems, we see the need to explore how the food system can be connected in whole cycles, that is, from table to farm as well. As mentioned above, Gliessman discusses what “our food system” would look like, if transformed so that it follows the basic thinking of agroecology. This is envisioned as the unfolding across five potential levels of transformation, where the first three address agroecosystem changes, and levels four and five target formation of more local and global food systems, respectively. Level four targets the local level food systems and creation of the above mentioned “food citizenship,” where food is grounded in a direct relationship between eaters and growers. Level 5, however, targets a wider change: “… build a new global food system, based on equity, participation, democracy, and justice, that is not only sustainable, but helps restore and protects earth’s life support systems upon which we all depend” . This vision for integrating webs of different food systems – whilst emphasizing the importance of fairness throughout the systems – becomes of high relevance in complex and multifunctional city-region food systems.There is much evidence of severe negative long-term environmental and social effects of our current globalized food system, for example, the feed and livestock production as one example . The ideas of agroecological food systems present alternatives to this, among others by contributing to local economic and resource circulation and inclusive, equitable food systems. Such systems should perhaps be described as “socio-agroecological food systems,” emphasizing the closely woven social, agroecological, and ecological interactions, for example, in terms of networks involving both farmers and non-farmers and between actors in the regions, no matter whether we talk ecological or political zones.

In Toronto, surveys showed that besides the typical local vegetables , farmers grew an additional 16 vegetable crops to supply the local community with foods unavailable in local grocery stores. These crops included Asian vegetables, such as bok choy, long bean, hairy gourd, and edible chrysanthemums and substantially increased the vegetative diversity of the urban garden system .Plant diversity is a principle predictor of insect diversity at small spatial scales , and plant diversity and small-scale structural complexity is important for tree-dwelling arthropods , ground-dwelling arthropods , web spiders , grasshoppers, bees, and ground-dwelling beetles . However, arthropod species richness has been shown to decrease with increasing impervious surface and intensive management in urban green areas, and intensive UA would presumably have a negative impact of species richness . In a study of urban backyard gardens in Toronto, invertebrate abundance and diversity was enhanced as the number of woody plant structures and plant species diversity increased, and backyard gardens had higher abundances of winged flying invertebrates when compared with urban grasslands and forests . Likewise, within domestic gardens in the UK, invertebrate species richness was positively affected by vegetation complexity, especially the abundance of trees . In Pennsylvania, butterfly diversity increased with native plantings within suburban gardens , and parasitoid diversity increased with floral diversity within urban sites . Because allotment gardens often exhibit a rich abundance of flowering plants and thus a prolonged season for nectar supply, allotment gardens can support urban pollinators for long periods of time . In a survey of 16 allotment gardens in Stockholm, the number of bee species observed per allotment garden ranged between 5 and 11, including a large number of bumble bees, which were observed on a total of 168 plant species,mobile vertical farm especially those in the Lamiaceae, Asteraceae, Fabaceae, Boraginaceae and Malvaceae . In a survey of gardens in Vancouver, a mean richness of 23 bee species were found across the different garden types sampled .

Similarly, community gardens in NYC were found to provide a range of ornamental plants and food cropsthat supported 54 bee species, including species that nest in cavities, hives, pith, and wood . In another study in NYC community gardens, the authors found that butterflies and bees responded to sunlight and floral area, but bee species richness also responded positively to garden canopy cover and the presence of wild/unmanaged areas in the garden . In Ohio, bee abundance in private, backyard gardens increased with native plantings, increases in floral abundance, and taller herbaceous vegetation . Overall, these studies support the idea that UA management with high vegetation diversity can have positive effects on invertebrate biodiversity in urban systems.Wildlife friendly features implemented in gardens can increase vertebrate diversity . Practices such as planting fruit/seed-bearing plants, limiting the use of pesticides and herbicides, and constructing compost heaps and bird tables increase bird and vertebrate abundance and diversity . Numerous avian studies have also shown that gardens with sufficient native vegetation can support large populations of both native and exotic bird species at the local level , and at the landscape level, garden heterogeneity can increase the overall diversity of insectivorous birds . Heterogeneity that includes native plant species may be particularly important, as studies of suburban gardens in Australia show that nectarivorous birds prefer native genera over exotic genera as foraging sites . For non-avian vertebrates, garden size and management style is critical for persistence in urban areas. Baker and Harris reported 22 mammalian species/species groups recorded in garden visitation surveys within the UK; however, mammal garden use declined as housing became more urbanized and garden size and structure decreased. Key findings from a range of garden studies show that in addition to high cultivated floral diversity, the three dimensional structure of garden vegetation is an important predictor of vertebrate abundance and diversity .

Increases in the vegetation structure and genetic diversity of domestic garden habitats have been shown to improve the connectivity of native populations currently limited to remnants and aid in the conservation of threatened species . For example, one study in Latin America documented that garden area and tree height were positively related to the presence and abundance of iguanas within urban areas, and increased patio extent allowed for greater iguana movement across the urban landscape . In addition to habitat quality, habitat connectivity may also affect the ability of ground dwelling animals to persist in the urban landscape ; thus, UA systems will need to be connected to other vegetated areas to allow for landscape movement. These studies show that garden structures or management practices that provide food and nesting resources or movement corridors can be important strategies for maintaining vertebrate diversity in cities.Ecosystem services are often a function of biodiversity levels , thus the composition, diversity, and structure of plant and animal communities within and around UA are important to consider for urban ecosystem service conservation. specifically, biodiversity provides opportunities for ecosystem services that city planners value–including energy efficiency, storm water runoff, air pollution removal, carbon storage and sequestration, and water quality provision . Within agricultural systems, ecosystem services like water storage, pollination, and pest control increase US crop production resilience and protect production values by over $57 billion per year . However, there remains a large knowledge gap around the provisioning of services in UA systems. This is especially concerning given increasing global food demands, climate-related crop failure, and consistent limitations in fresh food access within urban centers . We posit that UA systems provide a suite of ecosystem services, and that the extent and quality of the services are largely dependent on the biodiversity and vegetative structure of the UA system. Thus the form and management of urban gardens can radically influence service provision. Small garden patches are able to supply structural habitat diversity and carbon storage , while allotment gardens can potentially support ecosystem services such as pollination, seed dispersal, and pest regulation to the broader urban landscape .

In contrast, reductions in biodiversity can cause a reduction in the resilience of urban ecosystems overall . specifically, we review some of the most studied and important ecosystem services to the urban agricultural system: pollination, pest control, and climate control.As mentioned previously, urban agriculture can support a diverse assemblage of bees and butterflies , and the number of native flowering species can positively impact bee abundance and diversity . This may have large implications for fruit set and crop production given that crops experience higher or more stabilized fruit set in habitats with greater native bee diversity . Additionally, floral cover can positively impact conspecific pollen deposition by attracting a greater number of pollinators into an urban garden . Some studies suggest that pollinator foraging and dispersal needs are best supported by a network of small,hydroponic growing natural habitat fragments across urban areas . In general, bee foraging distance correlates with body size , and some larger bodied bees can regularly fly >1 km from their nest to forage on floral patches . Thus proximity to natural habitat can increase bee abundance, diversity, and pollination success for a wide range of crop species and may similarly impact bee diversity within urban landscapes. Research in rural and exurban habitats suggests that bumble bee nesting densities are positively impacted by the proportion of suburban gardens and wooded habitat and that bees are willing to forage further for high diversity flowering patches . Furthermore, both nesting density and dispersal are negatively impacted by the amount of impervious cover in a landscape , revealing the potential for urban landscapes to obstruct pollinator foraging and dispersal.Likewise, heavy development that leads to shaded and closed-off garden areas tend to limit local pollinator diversity . Overall, urban landscapes that maintain diverse natural habitat fragments and minimize impervious cover can promote bee nesting and dispersal. Insights from these studies and others suggest that pollination services may be higher in urban gardens if natural habitat patches and diverse flowering resources are available.Biological control is a method of controlling pest populations through the utilization of other organisms . Bio-control has been used for centuries within agricultural systems and could potentially enable sustainable crop production in cities without the reliance of toxic chemical pesticides. This is especially useful in high density urban areas where human exposure to toxins is more risky . The natural enemy complex responsible for bio-control includes predators, parasitoids, and pathogens that regulate pest populations . Different natural enemy taxa often have specific habitat preferences; therefore management for bio-control in urban areas requires knowledge of those factors that influence the abundance and richness of natural enemies.

One of the most effective groups of natural enemiesis parasitic Hymenoptera, which reduce herbivorous insect damage to urban trees, ornamental landscape plantings, and residential fruit and vegetable gardens . Bennett and Gratton showed that local and landscape scale variables associated with urbanization influence parasitic Hymenoptera abundance and diversity in residential and commercial properties along a rural to urban landscape gradient in Wisconsin. They found that parasitoid abundance was a positive function of flower diversity, and parasitoid diversity decreased as impervious surface increased in the surrounding landscape. This suggests that parasitoids benefit from increased floral resource availability and decreased impervious cover, similar to patterns described for pollinators.Below-ground natural enemies can prey on soil-dwelling stages of insect pests in urban lawns, often reducing the frequency and intensity of pest outbreaks . Yadav et al. tested if changes in urban habitat structure of gardens and vacant lots influenced below-ground bio-control services rendered by invertebrate and microbial communities. They showed that ants and microbial communities contributed a majority of the bio-control service, with ants exhibiting significantly higher bio-control activity than microbes, particularly in vacant lots. The high levels of below ground bio-control activity in vacant lots and urban gardens could serve as a foundation for building sustainable pest management practices for urban agriculture in cities. A number of other natural enemies provide bio-control services in UA landscapes, such as birds, bats, spiders and beetles , but there is still very little research done regarding their role in urban agriculture. The use of organic composts to support pest control by encouraging predatory species has shown some success . More work will be required to understand how urban systems, and especially urban agriculture, affect foraging behaviour in higher trophic level natural enemies .As climate models continue to indicate an increased likelihood of heat waves in urban areas, there has been great interest into the relationship between green infrastructure and mitigation of the urban heat island effect . Two main approaches have been proposed as solutions to reduce the urban heat island effect, maintaining more urban green space and reducing impervious surfaces. Increasing the proportion of green space within the urban matrix can reduce both surface and air temperatures . However, the variety of vegetative infrastructure, management, and plant species within UA systems will vary in their cooling potential. Akbari et al. predicted that up to a quarter of the cooling effect by urban trees in US cities are a result of garden/street trees contributing direct cooling of adjacent buildings, and this effect is dependent on tree size,species, maturity, and architecture. At the garden level, vegetation can influence the energy loads on individual buildings, but how this impacts air temperatures across the wider urban environment is still unclear . However, considering the potential impact that increased vegetation has toward regulating temperatures, there could be big implications on energy use and comfort levels for urban communities. Additionally, gardens located in areas unsuitable for buildings or established as buffer zones along rail corridors and highways, may be helpful in balancing the urban microclimate. Gardens also provide storm attenuation services to the urban matrix. Vegetation, trees especially, intercept intense precipitation and hold water temporarily within their canopy, thus reducing peak flow and easing demand on storm drains . In German cities, allotment gardens used on green belts to facilitate drainage have been shown to reduce heat and demand for air conditioning . In contrast, hard paving increases impervious surface, and in Leeds, UK, increased hard paving in residential front gardens has been linked to more frequent and severe local flooding .

As previously reported by Hauck et al. , Pst DC3000 did not induce strong callose deposition on its Arabidopsis plant host , although callose deposit frequency was significantly higher than in the water control . However, the Pst DC3000 type-three secretion system mutant induced 2.5 times more callose deposits than the wild type Pst DC3000 in Arabidopsis leaves . Altogether, our findings suggest that STm 14028s can induce a weak defense in lettuce leaves, similar to that of Pst DC3000 in Arabidopsis leaves. A major function of the SPI genomic region is to assemble the TTSS apparatus and encode effector proteins that could potentially suppress plant defenses. However, we observed that, unlike in the Arabidopsis-Pst DC3000 pathosystem where the TTSS is involved in suppressing plant immune response such as callose , the SPI-1 and SPI-2 regions of STm 14028s are not involved in this process in the lettuce system.Growth rates of STm 14028s, Mut3, and Mut9 in AWF and LSLB were determined during the log-phase of bacterial growth.As expected, there was minimal bacterial growth in water , indicating that residual nutrients in the inoculum were not transferred to LSLB or AWF to enhance growth. In an attempt to correlate the ability of the bacterium to survive within the apoplast with the ability to utilize apoplastic nutrients for growth, we included in this analysis Mut3 that contains a deletion of SPI-1 and adjacent genes and shows apoplastic persistence similar to the wild type STm 14028s .

When grown on LSLB,drainage pot both Mut3 and Mut9 had statistically significant lower growth rates than STm 14028s. Mut3, Mut9, and STm 14028s had growth rates of 2.78, 2.18, and 3.53 generations/hour, respectively . When grown in lettuce AWF, Mut3 and STm 14028s had similar growth rates, while the Mut9 growth rate was significantly lower . This finding suggests that the STm’s ability to persist in the apoplast may be linked to nutrient acquisition or the overall bacterial fitness in this niche that is dependent on yet-to-be determined gene and operon deleted in Mut9.The importance of food borne illness caused by contamination of produce by Salmonella spp. and the prevalence of contamination associated with leafy greens led us to investigate the molecular mechanisms allowing Salmonella spp. to use this alternate host for survival. As apoplastic populations of human pathogenic bacteria in lettuce are a potential risk for food borne illnesses due to persistence from production to consumption, we directed our focus on the bacterial internalization into leaves through stomata and endophytic survival. S. enterica internalization of leaves can occur through the stomatal pore . We were able to identify ten regions in the STm 14028s genome that may directly or indirectly contribute to the bacterium’s ability to open the stomatal pore facilitating its entry into the apoplast. Although it is not obvious which genes in those regions are specifically responsible for the observed phenotype on the leaf surface, the major metabolic functions of these regions are associated with sensing the environment, bacterium chemotaxis and movement, membrane transporters, and biosynthesis of surface appendices . Previously, these functions have been found to be associated with epiphytic fitness of bacterial phytopathogens . Furthermore, Kroupitski et al. observed that STm SL1344 aggregates near open stomata and uses chemotaxis and motility for internalization through lettuce stomata. Additionally, darkness prevents STm SL1344’s ability to re-open the stomatal pore and internalization into the leaves possibly due to the lack of chemo attractant leaching through closed stomata .

These findings suggest that close proximity to stomata may be required for Salmonella to induce opening of the pore. Therefore, STm invasion of the apoplast may be a consequence of a combined behavior of the bacterium on the phylloplane that can be modulated by plant-derived cues and,with this study, we have defined key genomic regions involved in this complex process. Not all the genomic regions required for initiation of the leaf colonization are essential for continuing bacterial survival as an endophyte . For instance, genes deleted from Mut3 and Mut6 [encoding unspecified membrane proteins, the PhoP/Q two-component system, SopE2 , phage genes, a transcriptional repressor , and some unspecified transporters] do not contribute to endophytic survival. Thus, these regions missing in Mut3/6 are potential targets for disrupting leaf surface colonization, but not endophytic persistence. This observation is not entirely surprising as the phylloplane and the apoplast environments are unique and they pose different challenges for bacterial survival in these niches. STm seems to have metabolic plasticity for adaptation to varying conditions in the leaf. For instance, STm SL1344 can shift its metabolism to utilize nutrients available in decaying lettuce and cilantro leaves and STm 14028s uses distinct metabolism strategies to colonize tomatoes and animal infection . We also observed that seven regions of the STm 14028s genome have opposite effects on the different phases of colonization. Mut1/2/4/5/7/8/10 seem to lack the ability to promote penetration into the leaf , but they show better fitness than that of the wild type strain in the apoplast . One hypothesis is that the increased bacterial population titers are due to lack of energy expenditure for maintaining large genomic segments that are not essential for survival as an endophyte, so that the excess energy can be spent on survival. However, this indirect effect of the deletion may not be valid for Mut4/10, where only small genomic regions are missing . Alternatively, these regions might encode for proteins that negatively affect bacterial survival in leaves.

This interesting observation is worth future investigation. Intriguingly, we found that genes deleted in Mut9 are important for re-opening the stomatal pore and successful endophytic survival. This deletion includes SPI-2 that functions in the production of the TTSS-2 apparatus, effectors, and a two component regulatory system of this island , which are important for the virulence of STm in animal systems . The contribution of the TTSS-2 apparatus and effectors to the bacterium’s ability to colonize the phyllosphere has been studied in several laboratories and it is largely dependent on the plant species analyzed . Nonetheless, so far there is no evidence for the ability of STm to inject TTSS effectors inside plant cells . Furthermore, the STm 14028s ssaV-structural mutant, that cannot form the TTSS-2 apparatus , survives in the lettuce cv. Romit 936 to the same extent as the wild type bacterium after surface inoculation . Our data also support the notion that the TTSS- 2 is not involved in STm ability to induce or subvert defenses, such as callose deposition in lettuce cv. Salinas . While studies in other plant systems have suggested that TTSS and encoded effectors may contribute to bacterial survival in the plant environment or in some cases are detrimental for bacterial colonization of plant tissues , it has become evident that the TTSS-2 within the SPI-2 region is not relevant in the STm 14028s-lettuce leaf interaction. It is important to note that SPI-2 is a genomic segment of roughly 40 kb with 42 open reading frames arranged into 17 operons . It is present in all pathogenic serovars and strains of S. enterica, but only partially present in species of a more distant common ancestor, such as S. bongori . Besides encoding structural and regulatory components of the TTSS-2 , SPI2 also carries genes coding for a tetrathionate reductase complex, a cysteine desulfurase enzyme complex, membrane transport proteins, murein transpeptidases, as well as genes with still uncharacterized functions . Thus, it is possible that genes and operons, other than the ones associated with TTSS-2,gallon pot may have a function in the bacterium colonization of the lettuce leaf. To date, it has not been demonstrated whether STm 14028s can access and utilize nutrients from the apoplast of intact lettuce leaves. Although nutrients in the apoplast might be limiting , it has been hypothesized that Salmonella may scavenge nutrients to persist in the plant environment and/or adjust its metabolism to synthesize compounds that are not readily available at the colonization site. For instance, a mutant screen analysis indicated that STm 14028s requires genes for biosynthesis of nucleotides, lipopolysaccharide, and amino acids during colonization of tomato fruits . Moreover, plants might secrete antimicrobial compounds into the apoplast as a plant defense mechanism, imposing a stressful condition to the microbial invader . Therefore, considering that subversion of plant defenses is not a function of the TTSS-2 in the apoplast of lettuce , it is possible that the Mut9 population reduces 20 fold over 21 days due to its inability to obtain nutrients from this niche and/or to cope with plant defenses. Although Mut9 shows reduced growth on lettuce leaf AWF , additional experimentation is required to distinguish between these two possibilities. It is tempting to speculate, however, that the tetrathionate reductase gene cluster within SPI-2 or the sulfur mobilization operon deleted in Mut9 might be involved in this process.

Particular to the ttr operon, TtrAB forms the enzyme complex, TtrC anchors the enzyme to the membrane, whereas TtrS and TtrR are the sensor kinase and DNA-binding response regulator, respectively . The reduction of tetrathionate by this membrane-localized enzyme is part of the Salmonella’s anaerobic respiration . Intriguingly, the use of tetrathionate as an electron acceptor during propanediol and ethanolamine utilization by the bacterium has been suggested to occur in macerated leaf tissue . A significant number of genes involved in the PDU ,EUT , and cobalamin pathways as well as the ttrC gene are upregulated in STm SL1344 when co-inoculated with the soft rot pathogen Dickeya dadantii onto cilantro and lettuce leaf cuts . Altogether, these findings suggest that these biochemical pathways may occur in both soft rot contaminated and healthy leaves. Considering that the encounter of the plant with a pathogenic bacterium triggers molecular action and reaction in both organisms overtime, it is not surprising that multiple regions of the STm 14028s genome may be required for lettuce leaf colonization. For instance, Goudeau et al. reported that 718 genes of the STm SL1344 genome were transcriptionally regulated upon exposure to degrading lettuce cell wall. In any case, further studies using single-gene mutants are still required to identify the specific genes and functions within each MGD mutant that are involved in the interaction between STm 14028s and lettuce cultivar Salinas. Butenolides are lactone-containing heterocyclic molecules with important biochemical and physiological roles in plant life. Although previously recognized as secondary metabolites, some types of butenolides were recently classified as plant hormones . Strigolactones are carotenoid-derived molecules bearing essential butenolide moieties that were originally described as chemical cues promoting seed germination of parasitic Striga species . It has since become evident that SLs are involved in controlling a wide range of plant developmental processes, including root architecture, establishment of mycorrhiza, stature and shoot branching, seedling growth, senescence, leaf morphology and cambial activity . SLs are synthesized via a sequential cleavage of alltrans-β-carotene by DWARF27 and the resulting 9-cis-β-carotene by MORE AXILLARY GROWTH3 and 4 . The SL precursor carlactone is then transported through the xylem and biologically active SLs are formed by MAX1 and its homologs and LATERAL BRANCHING OXIDOREDUCTASE . Cumulative evidence supports the idea that the DWARF14 α/β-fold hydrolase functions as a SL receptor and is required for the perception of the SL signal in Petunia , rice , Arabidopsis and pea . Upon binding, D14 proteins hydrolyze SL by action of its conserved Ser-His-Asp catalytic triad, followed by thermal destabilization of the proteins . As a consequence, the structural rearrangement of D14 proteins in the presence of SL enables the protein to physically interact with the F-box proteins MAX2 and SMAX1-LIKE  family proteins SMXL 6, 7 and 8 to form a Skp-Cullin-Fbox ubiquitin ligase complex that polyubiquitinates SMXLs and targets them for degradation by the 26S proteasome. The subsequent signaling events are largely unknown, but tentatively the mechanism is similar to other systems employing targeted protein degradation . In Arabidopsis, two paralogs of AtD14 have been identified . One paralog, KARRIKIN INSENSITIVE2 was identified in a mutant in Ler background which showed insensitivity to karrikin , a butenolide-type germination stimulant from smoke water . Although both AtD14 and KAI2 signaling pathways converge upon MAX2 and might employ similar mechanisms to transduce the signal, the two proteins regulate separate physiological events.

Over the course of the next few years, these data and observations will be cumulatively compiled across sites to determine if each plant has wide adaptability and appeal. Here especially, the Master Gardeners’ experience will be invaluable. They will be able to render an opinion on a plant’s garden-worthiness, as well as the response of the public to it over the course of its life in their garden. A plant thought interesting to an enthusiast may be completely unappealing to the average gardener, and might well prove unmarketable except at plant sales. That is not the plant we are looking for. On the other hand, if a plant performs well and has wide appeal, we can create demand from an educated gardening public for these environmentally friendly introductions before they are even in the retail outlets. In addition, the wide range of demonstration garden situations will give us a more comprehensive set of cultural recommendations for growers, landscapers and home gardeners. Some of the Master Gardener groups have already begun sharing information on the program and its plants through garden signage, newsletters and local radio programs. In most regions of the country, propagation and production development is the purview of the commercial wholesale nursery industry. In Georgia, growers are invited to the university managed test gardens each year to take cuttings of plants they are interested in and are encouraged to use their expertise to propagate and produce them . In Arkansas, the nursery industry actually provides the university with the initial plants for their introduction trials, and the university provides them with the results . In our case, we are trying to persuade both the commercial industry and the public to use environmentally responsible,square plastic pot low-input plants with which they may be unfamiliar. Because of this, some of the initial propagation hurdles may have to be cleared by university and extension research.

The highly successful Texas Coordinated Educational and Marketing Assistance Program is a good model for cooperation between the university and the ornamental horticulture industry . If a plant passes the various climate zone trials but is difficult to propagate, university and extension researchers tackle the problem until the best method is discovered. Graduate researchers at UC Davis and arboretum staff are continuing propagation research on our plants. Additionally, a commercial master propagator is currently working on protocols for several species, contributing the expertise of one who understands the requirements of mass production.Once a plant is ready for marketing, production schedules will be worked out to ensure sufficient supply to meet the expected demand at introduction. The National Arboretum has a regional cooperative program whereby growers and universities in seven southeastern plant-hardiness zones evaluate and increase the stock of plants slated for introduction . To ensure that these new plants are carefully screened, the National Arboretum controls their release through Material Transfer Agreements and centralized data analysis. After that, all the parties with an interest are involved in all aspects of testing and production, especially stock increase. In this way they can be assured of supply to meet the demand once a release date is announced . In the hope of implementing at least part of the National Arboretum’s model, the California Center for Urban Horticulture and its director Dave Fujino are currently acting as coordinators for the program’s coalition, which comprises the UC Davis Arboretum, UCCE researchers, the previously mentioned commercial master propagator, several wholesale growers, a distributor and a horticultural marketing expert, all of whom have generously donated their time and resources. With the help of all parties, the first set of UC Davis Arboretum All-Stars is expected to be released in fall 2009.In the future, we hope to broaden the coalition of cooperating entities to include other botanical gardens, California Native Plant Society members, other university and junior college faculty with expertise in this area, and more members of the nursery and landscape industry with an interest in growing, selling and planting low-input plants. This model is based on several successful program examples such as those in Texas and Oklahoma, where candidates for field trials are put forth at annual meetings of large advisory committees composed of members from academia, extension services, botanical gardens and arboreta, professional landscape and nursery associations, and individual industry representatives.

In these states, this group analyzes the results of the trials as well, and decides which plants are actually worthy of introduction . Their goal, like ours, is to identify and promote plants that do well with minimal inputs throughout most of the state. In this way, all the parties who benefit from the trials and subsequent introductions can be included in the process from start to finish. California consumers are increasingly aware of the need for environmentally sustainable horticultural practices. A large part of this sustainability is the use of plants requiring no chemical inputs and less water, mitigating the chemical load in watersheds and the waste of our precious water. The UC system — with its associated Cooperative Extension, Master Gardeners and California Center for Urban Horticulture — is ideally suited to establish and coordinate a cooperative effort with the nursery and landscape industries to introduce California native and other low-input plants to this new generation of consumers. Though this program is in its infancy, it holds great promise for fulfilling its goals of providing both producers and consumers with a large variety of beautiful plant materials, with greatly reduced negative impacts to the urban environment, for years to come.Tea is amongst the most popular beverages in the world. In addition to the provision of phenolic compounds , it is an important source of caffeine and trace elements. The quality of green tea in terms of commerce and trade is merely governed by the ratio of polyphenols to free amino acids , in addition to numerous further compounds determining the flavour characteristics. The concentration of free AA is positively associated with GT quality and accounts for 10- 50 mg g-1 dry matter in marketed GT. Free AA principally contribute to the freshness and mellowness of the infusion and their profile is dominated by the rare amino acid theanine . The flavonoids in GT, which comprise 20-40% of dry matter of young tea shoots are dominated by catechins , accounting for 10- 30 % of the dry matter. Provision of nitrogen has far-reaching consequences for the performance of plants at the biochemical, ecophysiological and ecosystem level. Nitrogen strongly affects the use of environmental resources , and in many cases a competition has been observed between N and carbon allocation, which also led to the development of theoretical concepts, like the protein competition model and the carbon/nutrient balance model addressing the functional relationship between these pools.

Green tea represents an ideal model system to study such interaction both from an ecophysiological and applied point of view. Increasing N supply significantly raised total biomass production and the yield of young shoots , although this was solely attributed to an increased number of young shoots.Total N concentration increased and C/N ratio continuously decreased with increasing N supply. The concentrations of soluble carbohydrates in roots and mature leaves were significantly reduced in response to excessive N supply, due to the demand for assimilates for nutrient uptake,drainage collection pot assimilation and growth. The accumulation of AA in young shoots depended largely on the N status, and decreased significantly in plants supplied inadequately with N. Graphical vector analysis , allowing the contribution of growth-induced dilution and concentration effects on phytochemical concentration to be elucidated, indicated that increasing provision of N led to a genuine increase of AA synthesis, and this relation was particularly explicit when analysed on a ‘per shoot basis’. The anine always remained the predominant free AA, supporting its importance in long-distance N transport in tea plants. However, while its molar share of the total AA contents initially increased from 24 to 47 % with increasing provision of N, under conditions of excessive N supply its share was reduced to 38 %. A concomitant raise of the relative contribution of glutamine and arginine that increased to 20 and 15 % of the total free AA concentration, respectively, accompanied this change, which has also been observed in previous experiments . The accumulation of these amino acids, characterised by lower C/N ratios , most likely stems from metabolic adjustments to improve the C economy, as frequently observed in other woody plants. The higher demand for C skeletons under such conditions is further supported by an increasing PEPC activity. The major catechin was epigallocatechin gallate, followed by epigallocatechin, epicatechin gallate and epicatechin. Catechin was only present at low concentrations, similar to gallic acid . Overall, individual catechins exhibited a uniform response to the N treatments imposed; hence their profile was not significantly affected. Highest concentrations of catechins were detected at intermediate N supply, while a strong reduction was noted at the highest level of N supply that also led to maximal N concentrations and lowest C/N ratios. This response has also been observed in other plant species and discussed in relation to the protein competition model and the carbon/nutrient balance . GVA clearly indicates that the total content of PP per plant increased regardless of declining PP concentrations under abundant N supply, suggesting that a dilution effect due to biomass growth is involved.

Indeed, as the yield was strongly increased at excessive N supply, the PP accumulation on a ‘young shoot basis’ was strongly diminished. With respect to substrate availability and energy the C status has been discussed as a critical factor for the accumulation of phenolic compounds . Diverting the C flux to N metabolism is therefore an important factor contributing to the observed reduction in PP accumulation, and the declining availability of carbohydrates is also analogue to substantially increased concentrations of AA, which is further supported by enhanced activities of PEPC and glutamine synthetase under abundant N supply. The precursor of the phenylpropanoid pathway, free phenylalanine , increased in young shoots in response to increasing N supply, but the magnitude of this increase was much smaller than that of the major amino acids mentioned above. Surprisingly, activity of leaf phenylalanine-ammonia lyase , the key enzyme of the phenylpropanoid pathway, increased with external N supply and plant N status, and the relation of polyphenols accumulation to the activity of PAL was negative . In fact, activities of PAL and GS were highly correlated , which is interpreted as a positive influence of N supply on overall metabolic activity, rather than a mechanistic link between PAL activity and the accumulation of polyphenols. Nonetheless, elucidating the relationships among N supply, the accumulation of flavonoids, and the activity of enzymes involved in their biosynthesis in tea awaits further investigations. The results indicate that the balance between growth and secondary metabolism in tea plants is shifted toward increasing synthesis of growth-related compounds such as amino acids and proteins, while investment of C into secondary metabolites is not changing proportionally. The quality index PP/AA decreased curvilinearly with increasing N status and the C/N ratio in young shoots. While a high GT quality is associated with a low PP/AA ratio, the accumulation of free arginine in response to excessive N supply needs particular attention due to the adverse taste notes attributed to this amino acid. The food-energy-water nexus is a concept that acknowledges that food, energy, and water systems are inextricably linked, are dependent upon one another and in concert mediate access to resources as well as resilience of human-natural systems . A constraint in one system could not only affect economic security in that system but could inhibit access in another . Therefore, the nexus provides a powerful means to improve synergies in food, energy, and water production , to identify how stressing food, energy and/or water systems creates resource vulnerabilities and/or resource scarcities in all three, to understand and quantify the production of ecosystem services, and to develop climate adaptation strategies . However, historically, food, energy, and water systems have been pigeonholed politically as well as broken up into small disjointed pieces that cross political boundaries and do not align with bio-regions or watersheds .

We therefore tested whether strain 869T2 grown at 30 ◦C could enhance the growth of different Arabidopsis ecotypes and other plant species. In addition to Arabidopsis ecotype Columbia, three Arabidopsis ecotypes that are less susceptible to Agrobacterium tumefaciens infection, BL-1, UE-1, and Dijon-G, were selected to examine the growth promotion ability of strain 869T2. After inoculation with strain 869T2, the average value of the fresh weight , dry weight , rosette diameter , root length , number of leaves , total leaf area per plant , and leaf area per leaf of the three additional Arabidopsis ecotypes were 1.2- to 2.0-fold higher than control plants. These data further support the hypothesis that the presence of strain 869T2 in different Arabidopsis ecotypes has a positive impact on plant growth.Seedlings of ching chiang pak choi and pak choi from the Brassica genus were also inoculated with strain 869T2 to examine its effects on plant growth. At 27, 33, and 40 days after inoculation with strain 869T2, the average fresh weight and dry weight of above ground leaves of ching chiang pak choi were higher than those of the control plants . Furthermore, the average leaf length and width, petiole length and width, number of leaves per plant, total leaf area per plant, and leaf area per leaf were greater in the 869T2-inoculated ching chiang pak choi compared to the control plants . The results shown in Figure 3J,K demonstrate that the average plant height and width of the 869T2-inoculated ching chiang pak choi were also greater compared to the control plants. Similarly, after the ching chiang pak choi was inoculated with strain 869T2, the average values of root fresh weight, dry weight, and length were higher in comparison to control plants . Figure 3O–Q indicate that both the aerial and below ground parts of ching chiang pak choi were larger after inoculation with strain 869T2. Figure 3R also shows that the ching chiang pak choi inoculated with strain 869T2 grew faster and flowered earlier than control plants 53 days after inoculation.

Similarly, 25 liter pot after inoculation with strain 869T2, the pak choi grew larger, including larger and more numerous leaves, larger aerial parts overall, and longer and heavier roots . These data indicate that inoculation of strain 869T2 in two vegetables from the Brassicaceae family significantly improved their growth. Because B. seminalis strain 869T2 successfully colonized Arabidopsis and two types of plants from the Brassicaceae family and promoted their growth, we further examined whether strain 869T2 could promote the growth of plants from the Asteraceae and Amaranthaceae families. At 35, 43, 50, and 56 days after inoculation with strain 869T2, the fresh weight of the aerial parts of inoculated loose-leaf lettuce plants increased 12.7- to 46.6-fold compared to the 0-day post-inoculation plants . By comparison, in the mock-inoculated control plants, the fresh weight increased 8.0- to 36.0-fold over the same period . Similarly, the dry weight of the inoculated loose-leaf lettuce increased more than that of the control plants at 35, 43, 50, and 56 days after inoculation . These data indicate that inoculation of the loose-leaf lettuce with strain 869T2 significantly enhanced plant growth. The weight increases of the inoculated loose-leaf lettuce plants were due to increases in average leaf width and length , the number of leaves per plant , total leaf area per plant and per leaf , and plant height and width . Furthermore, the root fresh weight of the inoculated loose-leaf lettuce plants increased 4.5- to 12.4-fold at 35, 43, 50, and 56 days after inoculation compared with the 0-day post-inoculation plants ; in contrast, that of the mock-inoculated control only increased 2.5- to 8.5-fold compared with the 0-day post-inoculation plants . Additionally, the root dry weight and length increased more in the inoculated loose-leaf lettuce plants than in the control plants . As seen in Figure 4M–O, overall plant size and leaf size increased after inoculation with strain 869T2, suggesting that strain 869T2 improves loose-leaf lettuce growth.

The results shown in Figures S4 and S5 demonstrate that both kinds of lettuce grew taller and wider, had more and larger leaves, and had heavier aerial and below ground tissues after inoculation with strain 869T2 compared with the control plants. The chlorophyll contents of red leaf lettuce leaves were also higher in the 869T2-inoculated plants than the control plants . These data collectively indicate that the three evaluated kinds of lettuce can grow significantly better after inoculation with strain 869T2. We also selected Chinese amaranth of the Amaranthaceae family to test the effect of strain 869T2 on its growth. At 36, 43, and 50 days after inoculation, the fresh weight of the 869T2-inoculated Chinese amaranth exhibited a 20.0- to 56.6-fold increase when compared to the 0-day post-inoculation plants, whereas the control plants only showed an 8.3- to 33.5-fold increase when compared to the 0-day post-inoculation plants . Other plant growth parameters of the 869T2-inoculated and control plants were also examined 36, 43, and 50 days after inoculation . Figure 5 illustrates that the 869T2-inoculated Chinese amaranth individuals had more and larger leaves, were taller and wider, and had heavier and longer roots than the control plants. These data show that inoculating strain 869T2 into Chinese amaranth promoted its growth.Because B. seminalis strain 869T2 promoted the growth of several leafy vegetables, we next tested the effects of the strain 869T2 on the flowering and fruit production of hot pepper and okra . Hot pepper plants, from the Solanaceae family, were inoculated with strain 869T2 but we did not observe significant growth promotion effects on the aerial and root parts of the plants. However, we did observe that the 869T2-inoculated hot pepper plants flowered 20 days after inoculation; the number of flowers continually increased and had more than a 7-fold increase at 37 days after inoculation . In the mock-inoculated control plants, we observed flowering 21 days after inoculation, and the number of flowers had only increased 5-fold at 37 days after inoculation .

The average number of fruits on the 869T2-inoculated plants was higher than that on the control plants at 30, 37, 44, and 51 days after inoculation . The average numbers of flower buds, flowers, and fruits per plant were higher in the 869T2-inoculated plants than in the control plants beginning 21 days post-inoculation . Furthermore, the percentages of hot pepper fruits with red and green/yellow coloring were higher in the 869T2-inoculated plants than in the control plants 59, 66, 73, and 80 days after inoculation . Similarly, the average anthocyanin contents of the 869T2-inoculated plants were significantly higher than those of the control plants at 66, 73, and 80 days after inoculation . However, the average length, width, and fresh weight of the fruits were not significantly different between the inoculated and control plants . Collectively, these data suggest that the inoculation of hot pepper with strain 869T2 could increase flowering and fruiting in hot pepper plants and accelerate fruit maturation.We subsequently examined the effects of strain 869T2 on okra, which belongs to the Malvaceae family. The overall plant size and weight were not significantly different between the 869T2-inoculated and control okra plants. We observed, however, that the number of nodes of the first flower was smaller in the 869T2-inoculated okra than in the control plants, suggesting that the 869T2-inoculated okra plants flowered earlier than the control plants . In addition, the average fresh weight and diameter of the fruits from the 869T2-inoculated plants were greater than those of the control plants , although the average fruit lengths were similar. These data demonstrate that the okra fruits became heavier and wider after inoculation with strain 869T2. In summary, inoculation of strain 869T2 into hot pepper and okra plants could cause plants to flower at earlier growth stages. The members of the genus Burkholderia belong to the class β-proteobacteria and have a broad distribution, residing universally in soil, water, and in association with plants, fungi, animals, and humans. Some Burkholderia species are plant pathogens in many vegetables and fruits, while others have been reported as opportunistic pathogens of humans and other animals. However, many other Burkholderia species are beneficial to plants, suppressing plant diseases and promoting plant growth by various processes, including the productionof antibiotics, secretion of allelochemicals,25 liter plant pot induction of pathogen resistance in plants, nitrogen fixation, or enhancing nutrient uptake by host plants. These beneficial Burkholderia species are free-living or endophytic and form mutualistic associations with their host plants. Burkholderia species’ high versatility and adaptability to different ecological niches rely on the high genomic plasticity of their large multi-chromosome genomes and the production of various bacteria secondary metabolites. In this study, we characterized the endophytic bacterium Burkholderia seminalis strain 869T2 isolated from vetiver grass, which was recently described and included in the Burkholderia cepacia complex . We have documented the IAA production, siderophore synthesis, and phosphate solubilization abilities of B. seminalis strain 869T2. Inoculations of strain 869T2 into tested plants demonstrated the plant growth promotion ability of this bacterium in several plant species from the Brassicaceae, Asteraceae, and Amaranthaceae families. Plant endophytic bacteria can increase the nutrient uptake and biomass accumulation of host plants through the production or regulation of various plant hormones, such as auxin, cytokinin, gibberellins, and ethylene. Indole acetic acid is a naturally occurring auxin produced by several endophytic bacterial species through the L-tryptophan metabolism pathway. Tryptophan can exist in the exudates of plants and is utilized by the bacteria to synthesize auxin, which enhances the growth of host plants. Auxin is the major plant hormone that regulates various aspects of plant growth and development, such as root initiation and development, leaf formation, fruit development, floral initiation and patterning, phototropism, and embryogenesis.

Several plant-growth promoting bacteria can synthesize IAA, including Bacillus, Burkholderia, and Pseudomonas species. In this study, Burkholderia seminalis strain 869T2 was able to synthesize approximately 2.0 to 2.2 µg mL−1 IAA in the presence of tryptophan and increased both the above ground and below ground biomass of tested plant tissues. Several previous reports also demonstrated that low levels of IAA stimulated primary root growth. Similar to our observations, the Burkholderia sp. SSG that was isolated from boxwood leaves produced 2.9 to 4.5 µg mL−1 of IAA with tryptophan and had plant growth promotion ability in three boxwood varieties. Additionally, Burkholderia phytofirmans strain PsJN, which was isolated from onion roots, showed higher IAA production, around 12 µg mL−1 , with the addition of tryptophan and improved the growth of potato, tomato, maize, and grapevines. Other Burkholderia seminalis strains can also synthesize IAA and have been reported to increase rice and tomato seedling growth. These previous studies, along with our observations, suggest that B. seminalis strain 869T2 may be similar to other Burkholderia species and other plant-growth-promoting bacteria that utilize IAA to increase root growth, which may assist host plants in taking up nutrients from the surrounding environment and improve aerial tissue growth. Consistent with this hypothesis, we observed that plant size, height, fresh weight, dry weight, and total leaf areas of several tested plant species all significantly increased after inoculation with B. seminalis strain 869T2. It is known that the IAA can positively affect cell division, enlargement, tissue differentiation, root formation, and the control process of nutrition growth. The IAA can also function as a signal molecule to influence the expression of various genes involved in energy metabolism and other plant hormone synthesis, such as gibberellin and ethylene. Interestingly, we observed earlier flowering in the 869T2-inoculated hot pepper and okra plants, suggesting that acceleration of plant growth rates might occur in these plants. In the future, transcriptome analysis of plant hormone response genes and energy-metabolic-related genes in the 869T2-inoculated plants might help us further decipher the possible mechanism of plant growth promotion ability of strain 869T2. From the results of our study, we observed that B. seminalis strain 869T2 had a better IAA yield at a temperature range of 25 ◦C to 37 ◦C and pH of 6 to 9. Similarly, Burkholderia pyrrocinia strain JK-SH007 reached the maximum production of IAA at 37 ◦C and pH 7.0.

A recent report shows that transient expression of the type three effector of Salmonella 14028 SseF in tobacco plants elicits HR, and this response is dependent on the SGT1 protein . This study suggests that SseF can induce resistant-like response in plants and requires resistance protein signaling components. Üstün et al. and Shirron and Yaron also showed that Salmonella 14028, which is able to deliver the SseF effector, cannot induce HR or any disease-like symptoms in tobacco leaves. Thus, it remains to be determined what would be the biological relevance of ETI in the Salmonella and other human pathogenic bacteria in their interaction with plants in nature.Although S. enterica and E. coli O157:H7 have not been traditionally known to be closely associated with plants and modulate plant’s physiology, the evidence tells us otherwise. An arms-race evolution in both the human pathogen and the plant is therefore, expected. A few studies have addressed whether genetic variability among plant species or within the same plant species can be correlated with differential bacterial behavior and/or colonization of plants. Barak et al. described that different tomato cultivars can harbor different levels of S. enterica population after inoculation via water indicating plant factors may control the ability of bacterial to colonize the phyllosphere. However, they also found that the cultivar with the smallest S. enterica population also had the lowest number of speck lesions when infected with the tomato pathogen Pst DC3000 , suggesting that strong basal defense in this cultivar may account for low bacterial colonization. On a comparative study of S. enterica contamination of several crop species, Barak et al. reported that seedlings from Brassicaceae family have higher contamination than carrot, tomato,vertical farming equipment and lettuce when grown on contaminated soil.

Seedling contamination correlated with the Salmonella population in the phyllosphere of all crop species, except tomato. Golberg et al. reported variations in internalization of Salmonella SL1344 in different leafy vegetables and fresh herbs using confocal microscopy. Internalization incidence was high in iceberg lettuce and arugula, moderate in romaine lettuce, red lettuce, basil, and low in parsley and tomato. Attraction to stomata was seen in iceberg lettuce and basil, not in arugula, parsley, and tomato. Brandl and Amundson reported that the age of romaine lettuce leaves is correlated with population size of E. coli O157:H7 and S. enterica Thompson on leaves.These authors also observed that exudates on the surface of younger leaves have higher nitrogen content than that of older leaves, which may contribute to determining the bacterial population size on the leaf. Thus, it is tempting to speculate that the genetic variability existent among plant genotypes regarding the chemical composition of their organ exudates may be a determinant for human pathogen behavior and ability to colonize plants. Finally, Mitra et al. studied the effect of different methods of inoculation on internalization and survival of E. coli O157:H7 in three cultivars of spinach. Among the organs studied, the spinach phylloplane and the stem provided the most and least suitable niche for this bacterium colonization, respectively. Although the leaf surface was the best “territory” for E. coli, the leaf morphologies of each cultivar affected the ability of this bacterium to survive. Collectively, all these studies point out that the plant genotype, age, leaf morphology, chemical composition of exudates, and the primarily infected organ affect the outcome of bacterial colonization of plants and the process may not be a generalized phenomenon, consequently shaping specific human pathogen and plant interactions.

For the past 43 years, people from across the U.S. and around the world have come to UC Santa Cruz to learn organic farming and ecological horticulture skills and concepts. What began in 1967 as the UCSC Student Garden Project, an informal student apprenticeship with English gardener Alan Chadwick, has since grown into the internationally known Apprenticeship in Ecological Horticulture, offered each year through the Center for Agroecology and Sustainable Food Systems . The six-month, intensive program combines hands-on and classroom work, covering topics ranging from soil fertility management, crop selection and culture, pest and disease management, and greenhouse and irrigation skills, to business planning, marketing, and food system issues. Apprentices work alongside instructors, learning in an “I do, we do, you do” model at the 25-acre UCSC Farm and 3-acre Alan Chadwick Garden. Since its founding, more than 1,300 people have graduated from the Apprenticeship, and have gone on to a variety of careers in sustainable agriculture and food systems-related work. Although CASFS staff members have informally tracked the activities of the Apprenticeship program’s graduates, there has never been a formal survey to find out how Apprenticeship alumni are applying their training and how the program has contributed to their work, volunteer, and personal activities. In 2009 CASFS undertook a comprehensive survey of alumni both to document the impacts of the program and to get suggestions for ways to improve the Apprenticeship. The survey was designed to address two basic questions: Is the Apprenticeship contributing to a more sustainable food system? To what extent did the program contribute to alumni’s activities? A grant from the Foundation for Global Community provided support for the survey and analysis.

The survey found that program graduates are making a major contribution to creating a more sustainable food system. This is reflected in the significant number of alumni involved in a wide range of sustainable food and agriculture efforts, and particularly in teaching others about food production and sustainable food systems. This brief summary provides an overview of the Apprenticeship alumni survey methods and results. A series of graphs detailing the results, with a focus on what all of the respondents have been doing since graduating from the program, is available online at the CASFS website.a A more in-depth analysis of the results and implications for education are presented in, “Achieving Program Outcomes? An Evaluation of Two Decades of Apprenticeship in Ecological Horticulture at the University of California, Santa Cruz Farm and Garden,” by CASFS researcher Jan Perez, UC Davis postdoctoral student Damian Parr, and UCSC graduate student Linnea Beckett, which appears in the inaugural issue of the Journal of Agriculture, Food Systems and Community Development.The survey was designed collaboratively with CASFS staff and input from alumni. Overall, 23 alumni and others pretested versions of the survey. The final survey included both quantitative and open-ended questions. All past apprentices since the founding of the program in 1967 comprised the survey population for the project; this included an estimated 1,200 alumni as of the survey date. The survey was sent to the 648 alumni for whom there was a known email address, drawn from an alumni database that was created in 1997 and updated recently for fundraising efforts and alumni activities. The survey was implemented between June 18 and July 20, 2009.The survey drew a response rate of 60% , which is considered high for a self-administered survey. Approximately 25% of graduates in each class since 1989 responded, with the most responses from those who had graduated in the past 10 years. Respondents were generally European-American, under 30 years of age during their Apprenticeship, from a middle-class or upper-middle class background, and had a 4-year college degree when they started the program .Since finishing the Apprenticeship, 87% of respondents are currently or have been involved in the field of sustainable agriculture and food systems work . Eighty percent volunteered for activities that contribute to sustainable food systems, and 99% used what they learned during the Apprenticeship in their personal lives. In addition, 48% of the alumni from the past 20 years had initiated, created,macetas para fresas or started the work or effort in which they were involved, which speaks to the leadership role that many have assumed since graduating .d Of the 315 respondents who are or have been involved in sustainable food and agriculture work, 93% reported doing some type of farming or gardening work since graduating. Primary job areas include food production , education , landscaping/gardening , retail , and work with non-governmental organizations . People have worked in rural , urban , and peri-urban settings, with many alumni having worked in more than one place since graduating. Two hundred of the respondents reported owning or operating a farm or garden at some point since graduating. Of those people, most grow a mix of vegetables and fruits; they also produce flowers , fruit , animal products , and grain , while 12% are involved in animal production. Those who own or operate a farm or garden employ one or more distribution strategies. These include direct sales to stores or restaurants , farmers’ markets , community supported agriculture efforts , wholesale , farm stand , and farm-to-institution . In addition, 40% donated produce as part of their operation.Education plays a role in the work of a significant number of alumni: 64% of all survey respondents, and 74% of those working in sustainable food and agriculture, reported that they have had jobs that included education activities or programs—particularly around food production and food systems issues and knowledge—as part of their formal goals.

In addition, 55% of those involved in education state they are training future teachers and trainers of sustainable food and agriculture-related topics. These “training the trainer” efforts increase the impacts of the Apprenticeship far beyond those who graduate each year. In terms of influencing social justice, the survey asked alumni if they had attempted to implement various strategies into their sustainable food and agriculture system work, volunteer, or personal activities. Among the responses, 60% reported that they had attempted to increase access to healthy food for those with limited access; 56% had increased inclusion; 48% had addressed inequities in access to information; 45% had fostered sharing of power or ownership; and 41% had increased the income of small- and mid-scale growers. Since these activities could range from buying fair trade coffee to starting a non-profit, we also explored this issue more specifically. We looked at work, volunteer, and personal activities people listed, and identified when they included addressing needs of people who were traditionally under served, worked on hunger or food security issues, or used words such as just, fair, and diversity. At least 35% of the respondents met these criteria. In addition to work endeavors, 80% of alumni have been involved in volunteer activities related to sustainable agriculture and food systems. Thirty three percent report donating time or materials to gardens, farms, schools, and outreach efforts; 28% have been involved in alternative agriculture organizations, as either founders, board or committee members, or as participants in activities; and 17% have led programs, classes and workshops, or served as a mentor. Other volunteer activities include community organizing and international community service . The Apprenticeship has also had an impact on alumni’s personal activities. Fifty-two percent report that the Apprenticeship influenced their purchasing behaviors, including buying local, organic, fair trade, and seasonal foods, as well as supporting farmers’ markets, CSAs, and local farms. Other personal activities include growing their own food or helping others grow food , and educating others .When asked how the Apprenticeship contributed to their subsequent activities, the majority of respondents noted that the program provided knowledge and skills . Survey respondents also reported that the program significantly helped them confirm their values ; provided confidence in their skills and ability ; helped shape their career goals ; and provided a network of people/contacts . Program components identified as most helpful for contributing to Apprenticeship graduate Cathrine Sneed launched The Garden Project to serve former offenders. Today the San Franciscoarea program provides on-the-job training in gardening and tree care. Apprenticeship alumni Jered Lawson and Nancy Vail founded Pie Ranch near Pescadero, California. The educational farm connects urban and rural high school students with the source of their food and provides training in farming skills. alumni achievements are described in Perez, Parr and Beckett .f Based on responses from the last 20 years of graduates, 60% of alumni considered the “hands-on” emphasis to be important to helping them accomplish their post-graduation activities. The next most-cited important program components were the residential living aspect of the program , working with peers , course work , and working with teachers .g This survey confirms that many alumni are participating in creating more sustainable food systems in a variety of ways, including farming, gardening, and educating others.

The primary trade-off here is that xESM provides a higher fidelity model for multi-segmented missions given that it includes the costs for all mission segments where an item is carried, while the ALSSAT’s ESM calculation method does not include preceding mission segments ALSSAT. This result is especially important considering downstream bio-manufacturing options which show a reduced xESM metric in scenarios where predeployment is leveraged to reduce the cost associated with the transit. Additionally, our “bring everything” mission which does not rely on bio-manufacturing yields larger costs overall from increased stored food. All three scenarios have equivalent tr2 ESM and xESM; this shows that in the last leg of the journey, or in a segment that is not influenced by future operations, ESM equals xESM. While simplified, this captures many of the critical features necessary to demonstrate the need for ESM extension. In cases where inventory from one segment can be used to satisfy constraints in another segment, the ESM summation of separately optimized mission segments can be less optimal than an ESM optimized with an objective function that accounts for both segments and constraint functions containing both terms from both segments. Given that system mass analyses are often used in the preliminary evaluation of technologies, it becomes more important when considering bio-manufacturing platforms to leverage the xESM formulation to provide higher fidelity and more favorable metric. However, we also must clarify that the aim of exploring this example is not to make claims about a specific technology,hydroponic vertical garden but rather to provide an example for differentiating ESM and xESM.

So far, we have looked at the xESM framework for calculating segmented costs. Based on the scenario chosen, the xESM metric is ultimately determined based on some set of specific technologies that are used. Simpler cases, as the ones given in the examples assume that the behavior of a particular system is fully known on Mars and the operation of the systems is undisturbed by external factors. Although several systems can reliably be considered deterministic in this scope, effects such as micro-gravity might affect the dynamics of specific processes in a bio-manufacturing context. Moreover, each process possesses a set of faulty states, i.e., technical issues may cause a system to underperform significantly. Detailed analysis of novel systems, e.g., in the bio-manufacturing case, requires the description of the operation of systems using mathematical models. To this end, the xESM framework can be used both to analyze the cost of individual processes as well as the cost of integrated processes in any desired segment, as they operate in time. A simulation-based analysis, either some cost analysis of specific elements or some end-to-end optimization procedure, makes use of models to simulate the systems, the environment, and associated costs for achieving the mission objectives. As a remark, we should note that the sophistication of the simulated case study can vary. For instance, higher-level decisions can be optimized without the need for detailed models for individual components, while exact scheduling and operational decision-making should involve dynamical models for the various subsystems. This principle has been widely adopted in manufacturing settings for design and control. Parts of the costs not commonly accounted for in cost calculations for space missions like ESM are uncertainty and risk. The latter are important factors during the design phase as we need to ensure safety in a robust, worst-case setting.The use of the xESM framework helps guide the development and implementation of software for a reference mission architecture for long-duration human exploration of Mars. We recognize that this extension of ESM as a metric for mission scenario comparison is preliminary and not exhaustive in its scope.

We also note that no single analytical result such as ESM or xESM will be the sole factor in the technical specification or platform decision-making. The differences presented are important but modest and are in scale with the uncertainty of the quantities used as the inputs. In addition to the incorporation of mission parameters, specific constants and terms in our formulation are required, such as a more precise calculation of equivalency factors for cooling, power, volume, and crew time and distillation of the specifics for risk fractions. Future endeavors include a comprehensive optimization problem formulation and solution based on the xESM framework both for biologically and non-biologically driven missions. Moving forward, we hope that our extension of ESM provides the basis for continued systems engineering and analysis research for a more quantitative and inclusive design and optimization of long-term human exploration missions.Calcium in plants has essential roles affecting tissue mechanical strength and tolerance to biotic and abiotic stresses . Understanding Ca translocation and partitioning to the different plant parts with time and the factors affecting it has a high agronomic and economical value as it will allow improving Ca nutrition practices to give higher quality end products. Ca was shown to accumulate mainly in transpiring organs in a process affected by various environmental conditions at both the canopy and root level, and is considered to be coupled to water movement driven by transpiration although controversies still arise in that relation . Furthermore, as Ca moves mainly in the xylem, a transport conduit under negative pressure, any attempt to sample it en-route will cause cessation of flow. As a result, the use of cumbersome destructive methods, which has limited research scope due to time and space constraints, has brought only fragmented and/or circumstantial evidence . For example, using pressurized stem exudation and leaf bleeding Siebrecht et al.showed either diurnal pattern or spatial distribution but not both together. Looking into various nondestructive methods it was found that Ca nuclides are either incompatible or inapplicable.

As Strontium was found to behave in similar ways in plants as well as in the more complex environment of human clinical research , it was chosen to serve as Ca tracer. Having a high energy gamma emitting nuclide that can be detected outside the plant, remote sensing became feasible. Tomato plants were grown in the phytotron of the Hebrew University under controlled climate of day/night temperatures of 28/18°C and RH of 40/65% respectively. Each plant was grown in a 5 L container containing half-strength modified Hoagland solution and was continuously aerated. After three months, reaching approximately a height of 1.60 m and having three fruit bearing trusses, eight plants were transferred each to a 2 L cylinder filled with nutrient solution and moved to a growth room subjected to temperature of 24/16°C and RH of 40/80% during the day and night respectively. Air temperature and RH at plants vicinity were recorded continuously and VPD was calculated according to Lowe . Light was supplied between 08:00 to 20:00 by two cool mercury lamps at 400 µmole m-2 s -1 PAR. Plants were arranged in four pairs with the 1st plant of each pair placed on a weighing lysimeter and monitored continuously with momentary whole plant transpiration derived from weight loss. The 2nd plant was installed with an array of five gamma radiation detectors ,vertical vegetable tower each with a custom-made lead shield. The shielded detectors were mounted on a moveable platform positioned to target the following locations: 1) main stem below the 1st fruit truss; 2) main stem below 2nd fruit truss; 3) main stem below 3rd fruit truss; 4) first fruit of 2nd truss; 5) leaf petiole adjacent to 2nd fruit truss. The detectors were connected to a PC via a custom-made communication device and radiation activity was measured continuously. More details of the system can be found in Wengrowicz et al. . Radiation readings were resampled to one minute and filtered in parallel to the transpiration data to eliminate noise. After three days of acclimatization, radio-Sr solution with an activity of 0.25 mCi was diluted in 10 mL of distilled water containing 4 mM Sr 2; Merck, Germany and added to the nutrient solution of the 2nd plant around noon.Every few days the radiation measuring system was detached and moved to the 2nd plant of the next pair. An example of radiation readings from one plant on the day of application is shown in Fig. 1. Within 30 minutes after adding the mixed Sr and radio-Sr solution to the nutrient solution, a sharp increase in radioactivity was noticed in the lower-most stem detector . A similar pattern yet with about half the rate was observed 30 minutes later in the middle stem detector and another 30 minutes took the radio-Sr to reach the upper-most stem detector with half the rate of the previous. Starting at the top of the plant root system and accounting for the distances between the detectors along the stem, radio-Sr velocity is estimated to be 0.154 mm s-1 , 0.143 mm s-1 and 0.125 mm s-1 at the 1st, 2nd and 3rd stem detectors respectively. Fruit and leaf petiole detectors showed a slow radiation increase and as no clear arrival time was seen, velocity could not be defined. To emphasize changes in radiation activity, and omit background levels, time derivative of radiation readings were calculated. On the day following application , radiation rate increased already before lights were switched on , starting at the low stem detector and followed by middle and top stem detectors around 03:10, 04:20 and 05:30 respectively. Fruit and leaf petiole radiation rate increased around the same time however with a much lower rate. Initial daily rate was highest at the lower-most stem detector and decreased the further the stem detector was from the source, with fruit and leaf petiole the lowest.

Maximum rates were achieved around 10:00 following the same order of both timing and rates, excluding the fruit detector which showed a 2-fold rate compared to leaf petiole. Thereafter radiation rates dropped quickly only to show a 2nd smaller wave peaking towards 18:00 and subsiding towards evening. A third wave was clearly observed at the three stem locations after lights were switched off, with rates decreasing the further the detector is from the source. Transpiration rate pattern of a neighbor plant showed low rates during dark periods except from a noticeable swell starting around 03:30. During light hours, a rate increase with three distinct peaks can be seen which correlated nicely with room VPD . It should be noted that transpiration rate correlated with radiation rate patterns only until the 10:00 peak, suggesting thereafter a more complex relationship between sap transport and radio-Sr translocation. As time passed, radiation readings at the top-most stem, fruit and leaf petiole detectors increased. The middle stem detector showed in-large a saturation curve pattern, while the lower-most stem sensor, which measured the first few days the highest radiation increase, showed later a decline to level lower then those detected at above stem positions . To shed some light on the accumulative patterns, radiation rates on the 10th day after application are presented in Fig. 4. Lower-most stem detector exhibited negative predawn and morning rates yet a morning peak was still present. Rates climbed slowly towards zero during light hours and proceeded with an after-dark positive peak. The middle stem detector showed a similar pattern although being positive till the predawn drop to later “surface” above zero in the afternoon. The top-most stem as well as fruit and leaf petiole detectors showed positive rates throughout the day with a similar pattern as the other stem detectors. The sequential arrival of root applied radio-Sr to stem locations on the day of application clearly maps its flow path, whereas its decreased velocity along it suggests sap loss as it is being directed towards side organs as leaves and to a probably lesser extent, fruit trusses. As radio-Sr translocation rates were also reduced along the path, it is assumed that Sr was embedded in plant tissue, absorbed on cation exchange sites, and/or unloaded off the xylem causing sap Sr dilution. Throughout the following days, daily transpiration rate showed predawn increases with a possible link to circadian stomata opening resulting in a sap flush within the plant. Predawn translocation rate pattern depended on time that passed from application and detector location. On the first days, when Sr was still accumulating on available cation exchange sites within the stem tissue, translocation rates exhibited significant increase at all locations.

In separate studies NPR1 over-expression and enhanced resistance are correlated either with elevated or earlier expression of PR gene transcripts, thus supporting this theory . Along with stimulating PR gene expression and priming plants to respond to infection, high NPR1 expression levels enhance the sensitivity of plants to chemicals and fungicides including BTH, fosetyl, and Cu2 . NPR1 is also required for a BTH-induced defense priming indicating a great potential for coupling both chemical and transgenic disease strategies through plants expressing NPR1 . For instance, plants can be engineered to over-express NPR1 so that a lower chemical dose is required to confer efficient disease resistance. Genes with high sequence similarity to NPR1 can be found in Arabidopsis, tobacco, tomato, rice and maize suggesting that this regulator will be conserved among many plant species. Over expression of NPR1 in rice has been shown to enhance resistance to the rice bacterial blight pathogen Xoo . Studies with a putative rice homolog of NPR1 indicate that over-expression of the endogenous rice gene can also provide protection against Xoo . However, unlike in Arabidopsis, rice over-expressing NPR1 grown under sub-optimal conditions display a detrimental growth phenotype. These types of observations may predict an overall phenotype that will need to be further investigated when strongly over-enhancing SAR pathway components in plants . Together these data suggest that, in general,growing vegetables in vertical pvc pipe crop plants contain defense signaling components similar to those found in Arabidopsis.

Potentially, over-expression of other endogenous signaling components other than NPR1 may also be able to provide enhanced plant protection.Biotic infections that stimulate localized host cell death can stimulate SAR in a wide variety of plants, as indicated above. Similarly, root colonization by non-pathogenic Rhizobacteria, can stimulate induced systemic resistance . This resistance is distinct from SAR, but interestingly shares one of the same components, NPR1and can work additively with SAR to mount a heightened defense response . Induction of the ISR response requires that plants are able to properly respond to signals triggered by JA and by the plant hormone ethylene. ISR is not functional in Arabidopsis mutants that are nonresponsive to ethylene, although the SAR response remains intact . Presently, most work utilizing ISR with field grown crops focuses on bio-control. For example, when tomato plants or seeds are treated with dried Rhizobacteria spores, the severity of infection by the tomato mottle virus is reduced . It is notable that the ISR pathway shares components with other defense pathways. Thus, altering the amount of a single component involved in multiple pathways, such as NPR1, may have unintended pleiotropic effects, both favorable and unfavorable that will need to be addressed before application in the field. Plants induce defense responses not only against bacterial, fungal and viral pathogens but also against pests that can cause wounding. Thus, other biotic inducers of resistance include herbivorous insects. The chemical JA is important for triggering resistance to these pests . The defense pathways controlling insect defense and other induced responses are partially antagonistic.

Treatment of plants with SA and BTH can inhibit the induction of JA induced genes and conversely, application of JA reduces the defenses triggered by ISR inducers . However, it appears that the SA and JA pathways can also, in some situations, act in concert to promote defenses against at least a subset of pathogens. In Arabidopsis, in studies where both SA and JA are applied to a plant these chemicals can work additively to protect plants against Pseudomonas syringae pv. tomato . Potentially, upregulation of one induced resistance pathway may impart costs to a number of other pathways. With such complexity inherent in defense responses, it becomes clear that thorough field tests performed under multiple environmental, developmental and pathogen stressors will be essential for any plants engineered for enhanced resistance.Basic research is providing an ever-expanding arsenal of genes with which to engineer disease resistance. Several of these genes have already proven useful and more will undoubtedly be discovered. However, the limitations and costs to using this technology are just starting to be explored. A thorough understanding of these areas will be increasingly important as the tools identified by basic research in plant defense mechanisms are applied more frequently to commercial crops. Previously, only a few studies have attempted to look at the costs, for example, in fitness to plants induced for one of these resistance responses and even fewer still of these studies have been with the economically important cereal crops .Most of the genes involved in broad-spectrum resistance have yet to be inserted as transgenes into crops. Therefore, investigations into the costs of induced resistance have started by assaying the effects of using chemical inducers. Heil et al. have studied the fitness of wheat plants treated with BTH in the absence of pathogens.

When plants were grown either hydroponically or in the field, water-treated control plants were able to achieve greater biomass than their BTH-treated cohorts. In field experiments, however, significant growth differences were not seen until approximately 6 weeks after treatment. The authors suggest that many of the potential fitness costs associated with induced resistance responses may be masked in laboratory experiments where growth conditions are kept optimal, and support this hypothesis with experiments performed growing plants under differing nitrogen concentrations. In addition, when the age of the plants induced for SAR was considered it was found that the growth-costs of BTH treatment could be reduced if the BTH was applied after the lateral shoot formation was complete . These data also underscore the importance of factoring plant developmental programs into any efficient strategy to enhance plant resistance by chemical treatment or genetic engineering.Another unwanted effect that may arise from transgenic manipulation of genes involved in defense signaling pathways is spontaneous cell death. Spontaneous cell death has been uncovered in many genetic screens for enhanced disease resistance and recently, has been seen in transgenic plants. These mutants and transgenic plants are often collectively referred to as lesion-mimic mutants since they display lesions similar to those observed in a defense response even in the absence of pathogens. This form of cell death in plants is sometimes influenced by alterations in environmental conditions such as light, temperature and humidity . Therefore, both in basic research and in applied experiments, it will be important to understand the parameters controlling cell death. This research is critical not only for optimizing the situations where transgenes and chemicals will be most useful to generate disease resistance, but also to minimize negative effects on important agronomic factors such as development,vertical greenhouse fertility and yield. Several dicot lesion-mimic mutants that lead to enhanced cell death have been well characterized including the Arabidopsis acdand lsdmutants . A recessive mutation in the LSD1 gene leads to a lesion-mimic phenotype that is triggered under long-day light conditions and by treatment with SA and INA .

The lsd1 mutation appears to confer hypersensitivity to these compounds . It is hypothesized that reactive oxygen species accumulate in leaf tissues preceding formation of lesions and that LSD1 normally functions to define the extent of lesion spread by suppressing cell death . ROS accumulation is observed in the initial stages of plant defense responses including during the hypersensitive response . In wild-type plants, the HR precedes the formation of micro-lesions that are correlated with induced resistance and is associated with subsequent resistance to pathogen infection . Altered accumulation patterns of ROS in plants with heightened cell death or an HR suggest that ROS play a central role in regulating plant programmed cell death . Lesion-mimic mutants have also been identified in cereals including rice, maize and barley . In rice, one well-characterized class of lesion-mimics contains the slmutants . Many of the sl mutants display heightened resistance to M. grisea and increased expression of PR-1 and peroxidase genes . Other rice lesion mimic mutants displaying enhanced resistance are the cdrmutants . The cdr mutants also have elevated PR gene expression and cell cultures of the cdr mutants under certain conditions can accumulate H2O2. Thus, a subset of rice lesion mimics may have misregulated levels of ROS . Misregulation of ROS accumulation also occurs in transgenic rice engineered to express the OsRac1gene. Over expression of OsRac1 in a wild type stimulated H2O2 accumulation in leaf tissue and over-expression in an sl background stimulated cell death . While mutant rice genes leading to lesion-mimic phenotypes have only been hypothesized to play a role in ROS regulation, one lesion-mimic-inducing gene from maize, Les22, has been cloned. Les22 encodes a uroporphyrinogen decarboxylase , an enzyme required for chlorophyll and heme biosynthesis . Mutations in the homologous human enzyme lead to the light-induced skin toxicity condition of porphyria. People with mutations in the UROD are predicted to accumulate high levels of uroporphyrin III that upon light excitation can become highly reactive resulting in toxic levels of ROS. While the Les22 mutant phenotype does not appear to be associated with enhanced resistance to pathogens, a recessive Les mutant, les9, displays enhanced resistance to the pathogen, Bipolaris maydis . Another maize lesion-mimic mutant, lls1 , a recessive mimic mutation is associated with enhanced resistance to the maize rust fungus, Puccinia sorghi . The LLS1 gene was cloned and found to encode a novel protein containing two binding motifs resembling aromatic ring-hydroxylating dioxygenase regions suggesting that this gene may also be involved in detoxification, perhaps of a phenolic compound important in mediating cell death . Finally, pathogen resistance is associated with lesion-mimic phenotypes in not only rice and maize, but also barley.The mlo mutation confers a spontaneous cell death phenotype upon pathogen challenge and noticeable formation of structural appositions under epidermal cells. Thus, the mutant phenotype confers a rapid death phenotype to the cells, halting fungal ingress at the point of challenge and preventing a compatible interaction. The wild-type allele MLO prevents cell death when challenged by E. graminus . Many mutants showing lesion-mimic or enhanced cell death phenotypes are associated with enhanced disease resistance. This does not necessarily suggest that cell death is a requirement for defense, or that defense always de-represses cell death pathways. Simply, many defense components will likely have multiple roles in basic metabolism and stress responses throughout the plant that need to be characterized before utilizing these genes for resistance engineering.Many of the examples listed above, may appear as substantial challenges to engineering disease resistance, however, these challenges provide opportunities to create plants that are even more resistant than plants engineered based on our current knowledge. For instance if the already identified components of a signaling pathway are not the best candidates for durable resistance in the field, technologies such as micro-arrays will help to pinpoint novel targets of interest . When mutations involved in disease resistance have already been identified, but are recessive in nature such as the mlo, edr1 and mpk4 mutants, classical breeding strategies can be employed. These mutants cannot be placed into heterologous systems using transgenic technology but, as with gene-pyramiding, they are still useful in breeding. Or, as technology continues to improve, gene knockouts and silencing of homologs may be employed to generate mutants in diverse species. If research continues to suggest crosstalk between ISR, SAR and insect defense signaling pathways, there may be great potential for additive defense effects by manipulating overlapping components. So, while limitations and cost of engineering broad-spectrum defenses warrant much attention, it is useful to look at such challenges as means for streamlining and improving upon current engineering strategies.Another promising strategy for enhancing resistance in plants is the use of RNA homology-dependent silencing to combat viral and bacterial disease . The nature of this silencing has been evaluated in a number of systems where similar phenomena are called by different names; RNAi in animals and quelling in fungi . One conserved step leading to RNA homology dependent silencing is the formation of a double stranded RNA intermediate. This dsRNA intermediate is recognized by an enzymatic complex which targets degradation of all corresponding homologous RNA transcripts . Several cases detailed below illustrate the possibilities for generating disease resistant plants by taking advantage of this inherent biological process.

Synthesis of malate, however, may unduly tax a carbohydrate-limited root apex. Indeed, Ca2 treatment, which accumulated more NO3 – than the other treatments , contained negligible amounts of malate . In conclusion, NH4 + and NO3 – differentially affect the finescale spatial patterns of uptake, export, assimilation, and carbohydrate content along root apices. Moreover, although NO3 – levels are maintained low in the meristem and the apical part of the growth zone, NO3 – clearly needs to be considered as a significant component of the osmotic pool supporting expansion at the base of the growth zone and sustaining the functions of young, mature root tissues.Unlike most commonly occurring coconuts, the edible solid endosperm often called the ‘meat’ or ‘kernel’ is thicker, with a soft jelly-like texture at maturation. This can be attributed to some unusual physiological and bio-chemicaltraits. Makapuno contains high levels of cytokinins which promotes cell proliferation and expansion that results in greater endosperm thickness compared with normal coconuts . The unlimited growth of the solid endosperm makes Makapuno a model system for tumorigenesis studies in higher plants . Makapuno also lacks – galactosidase activity which leads to the accumulation of higher levels of the water-soluble galactomannan rather than the water insoluble mannan found in normal coconuts . This likely alters cell wall structure and adhesion and produces a highly viscous endosperm . Finally, Makapuno has a higher content of moisture and protein in the endosperm but lower crude fat; the latter trait should reduce rancidity which is important to those food processing industries that use coconut in their products .

These features of the Makapuno coconut are similar to ‘Kopyor’ in Indonesia, ‘Dikiri Pol’ in Sri Lanka, ‘Thairu thengai’ in India , Maphrao Kathi’ in Thailand and Dua Dac Ruot in Vietnam ,vertical planters for vegetables and are all known for their combination of good taste and unique ‘meat’ texture .The unique endosperm of Makapuno may be controlled by a single Mendelian recessive mutation . The described traits are only found in the triploid endosperm and all alleles need to be recessive. Makapuno therefore need to be physically segregated from normal coconut trees to prevent cross pollination. In addition, the highly viscous nature of the inner endosperm makes germination difficult. The need for a triploidhomozygous recessive state and the observed low germination frequency makes Makapuno coconuts a rarity in nature. The result is a sale price that is 3–5 times higher than normal coconuts in South East Asia and that can be 50 times higher than that of normal mature coconuts in Thailand. Although Makapuno is a value-added commodity,to our knowledge, the post harvest behavior of its fruit has not yet been studied. This is important because of the increased demand for fresh coconut fruit in distant markets in Europe and the United States . Previous work showed that normal mature coconut can be stored for 3–5 months post harvest under ambient atmosphere, after which, the liquid endosperm evaporates and the embryo germinates . De-husked mature coconut has a shorter storage life: up to 2 months at 0–1.5 ◦C, or 3 weeks at 12–15 ◦C . Although removal of the husk reduces shelf-life, the cost-benefit analysis is better. These fruit weigh less which lowers long-distance shipping costs and the price can be marked-up as the product is more convenient for the consumer. As described, Makapuno fruit has distinct properties compared to normal coconuts and this would be expected to influence the storage performance and conditions used to maintain its quality.

The overall goal of this study therefore, was to provide basic information on the storage conditions needed to prolong Makapuno coconut storage-life.Fully mature Makapuno coconuts were partially de-husked, leaving a layer of fiber 1–2 cm thick and were transported from Kanchanaburi province to the laboratory at Kasetsart University within 2 days of harvest. Six uniform and damage-free coconuts were packed in strong well ventilated fiberboard cartons with dividers to separate individual fruit and were then stored at 30 ± 2 ◦C, 66 ± 5% relative humidity . Individual fruit was examined for respiration rate, ethylene production rate, weight loss, color, total soluble solid contents , titratable acidity and lipid oxidation of coconut meat expressed as malondialdehyde values and decay at the initial day and 3 days after storage.The overall aim of this work was to determine the conditions necessary to extend the storage life of partially de-husked Makapuno coconuts after harvest. Our observation of Makapuno coconut maturation agreed with the findings of Islam et al. . Makapuno coconut reached early maturation ∼9 months after flowering and became fully mature ∼10–11 MAF. The endosperm is thicker and softer than that of normal coconut and the liquid endosperm filled the rest of cavity. Our data showed no significant difference in respiration and ethylene production of Makapuno coconut harvested between 9 and 11 MAF .Since there are no published data on the post harvest biology of Makapuno that we are aware of, this work is the first evaluation of the compositional, physiological and biochemical changes in Makapuno coconut fruit after harvest. During 3 days of storage at 30 ◦C, the rates of respiration and ethylene production for Makapuno were similar to those reported for normal mature coconut genotypes . However, the respiration rate from disks of Makapuno coconut was found to be higher than that of intact whole fruit.

This may be due to differences between whole fruit and disks in term of the amount of surface area exposed to the atmosphere or the gas transmission and gas solubility through the tissues. Post harvest fruit quality can be partially assessed by evaluating SS, TA and weight loss. The SS of de-husked normal coconut declines but TA increases as the post harvest storage period increases . Normal harvested mature coconuts lose weight gradually over the storage period due to water evaporation from the fruit cavity or due to absorption by the kernel . In contrast, Makapuno coconut in this study exhibited less weight loss probably due to the viscosity of the endosperm, which restricted water loss through evaporation . Consequently,the color, SS and TA of Makapuno meat did not significantly change after 3 days of 30 ◦C storage. One of the major problems with coconut storage is the increasing rancidity of the endosperm that results from lipid oxidation i.e. the oxidative deterioration of lipids. This leads to an undesirable taste and smell during storage. Malondialdehyde is used as an indicator of lipid peroxidation , and generally, higher MDA levels correlate with higher rancidity . Although insignificant , the MDA of the meat increased 2-fold after 3 days at 30 ◦C storage. Compared to other coconuts, lipid oxidation is less problematic for Makapuno during storage,vertical farming technology probably due to the lower crude fat relative to non-Makapuno types . Another major problem of harvested coconut is decay. Deterioration of Makapuno fruit was evident as mold infestation on the husk surface, which also penetrated the fruit ‘eye’ after they were transferred to 30 ◦C for 3 days . The most prevalent fungal molds found on Makapuno husks were Aspergillus spp. and Penicillium spp. but Fusarium spp. and Curvulria spp. were also detected . Treating fruits with 3–5% sodium metabisulfite or linear low-density polyethylene—file wrap could not prevent surface mold or extend Makapuno coconut storage life when stored at 30 or 5 ◦C .As expected, fruit storage-life increased with decreasing temperature. At 5 ◦C the rate of respiration and ethylene production was reduced 3–6 fold and the storage life was increased to 42 days when stored at 5 ◦C rather than 3 days at 30 ◦C. Moreover, following transfer from 5 to 30 ◦C, respiration rates were similar to fruit kept continuously at 30 ◦C and ethylene production did not change , indicating that there was little or no chilling injury using these temperatures and storage times . During the 6-week storage period, fruit weight loss was significant but endosperm color, SS, TA and decay incidence were similar to those that were stored at 30 ◦C for 3 days. This may indicate that most of weight loss caused by loss of moisture from husk but not from the endosperm. Makapuno fruit developed symptoms consistent with post harvest chilling injury when stored at 2 ◦C for 4 weeks. Cold-stored fruits transferred to 30 ◦C for an additional 3 days exhibited signs of deterioration: the meat developed a woolly texture, and a rancid smell and taste coincided with higher MDA and decay scores. Thus, 2 ◦C was more unsuitable for Makapuno coconut storage than 5 ◦C.Generally, enclosing fruit in films, bags or coatings reduces water loss, prevents the spread of disease among batches of stored fruit and establishes an atmospheric composition that slows down deterioration . It was previously reported that high-OTR bags can enhance the shelf life of mature coconuts . To determine the effect of high-OTR on Makapuno coconuts quality,fruits were stored individually in high OTR bags and kept at 5 ◦C and compared to unbagged fruits held at 5 ◦C.

Coconuts in high-OTR bags had a high O2 transmission rate which allowed O2 to escape from the bag resulting in low O2 accumulation inside. Ethylene also accumulated, but the concentration was lower than 0.15 ppm. While the unbagged Makapuno coconut could be stored only for 6 weeks at 5 ◦C, Makapuno coconut kept in high-OTR bag and stored at 5 ◦C lasted for 10 weeks without any sign of deterioration. In addition, high OTR bag and 5 ◦C storage minimized evaporation very effectively as there was almost no weight loss after 10 weeks and there was no change even after transfer to 30 ◦C for 3 additional days . This reduction in weight loss is likely due to the high relative humidity maintained inside the bag. The combination of high-OTR bag and 5 ◦C effectively suppressed the growth of microbes probably via protecting the coconut from direct contact with fungi and preventing moisture condensation on husk surface. The CO2 and O2 concentration were not high or low enough to kill the fungi therefore it is unlikely that the modified atmosphere would affect fungi pathogen metabolism. The MA provided by the high-OTR bag also maintained SS, TA and MDA levels even after transfer to 30 ◦C. After 10 weeks storage in high OTR bags, fruit quality was maintained and coincided with a reduction in water loss. Thus it is hypothesized that the reduction in water loss might be the most important factor prolonging Makapuno storage life when stored in high OTR bags. However, conclusive proof of this hypothesis requires further experiment.What was once limited to the realm of science fiction and theoretical astrophysics models is now within an operational vision of exploring the “final frontier,” otherwise known as outer space. With the advent of cost-effective launch technologies and the gradual deregulation of space launches and flights, the global economic activity in the space industry has begun to surge. While satellite services likely comprise most viable and profitable venture in space, the adoption of novel space-based goods and services, from space tourism to organ bio-printing, show tremendous potential to disrupt even incumbent industries on Earth. The global space industry has increased in value from $162 billion in 2005 to $469 billion in 2021. While government spending increased 19% to add $107 billion to the space industry, much of the value growth can be attributed to the private sector: commercial enterprises provided an estimated $224 billion in goods and services and $138 billion from constructing infrastructure and support . The most recent space industry reports by Citi and Morgan Stanley project a $1 trillion valuation and $100 billion in annual revenues by 2040 . Space-related research and development has expanded dramatically based on the 22% annual increase for the past five years attributable to the private sector, in contrast to the 10% increase for U.S. governmental expenditures in nominal dollars . While NASA and public sector expenditures have stagnated $12 billion2 in the past few decades, “NewSpace” companies,3 or new companies emerging in the private space industry, have invested an estimated $5-6 billion in 2020, up from less than $1 billion in 2010 .