Plant health sensing

If plants are to be used as a food source for long term space missions, they must be grown in a stable environment where the health of the crops is continuously monitored. The sensor(s) to be used should detect any diseases or health problems before irreversible damage occurs. The method of analysis must be nondestructive and provide instantaneous information on the condition of the crop. In addition, the sensor(s) must be able to function in microgravity. This first semester, the plant health and disease sensing group concentrated on researching and consulting experts in many fields in attempts to find reliable plant health indicators. Once several indicators were found, technologies that could detect them were investigated. Eventually the three methods chosen to be implemented next semester were stimulus response monitoring, video image processing and chlorophyll level detection. Most of the other technologies investigated this semester are discussed here. They were rejected for various reasons but are included in the report because NASA may wish to consider pursuing them in the future

Controlled Ecological Life Support Systems: Natural and Artificial Ecosystems

The scientists supported by the NASA sponsored Controlled Ecological Life Support Systems (CELSS) program have played a major role in creating a Committee on Space Research (COSPAR) section devoted to the development of bioregenerative life support for use in space. The series of 22 papers were sponsored by Subcommission F.4. The papers deal with many of the diverse aspects of life support, and with outgrowth technologies that may have commercial applications in fields such as biotechnology and bioengineering. Papers from researchers in France, Canada, Japan and the USSR are also presented

Effects of CO2 enrichment on photosynthesis, growth, and nitrogen metabolism of the seagrass Zostera noltii

Seagrass ecosystems are expected to benefit from the global increase in CO2 in the ocean because the photosynthetic rate of these plants may be C-i-limited at the current CO2 level. As well, it is expected that lower external pH will facilitate the nitrate uptake of seagrasses if nitrate is cotransported with H+ across the membrane as in terrestrial plants. Here, we investigate the effects of CO2 enrichment on both carbon and nitrogen metabolism of the seagrass Zostera noltii in a mesocosm experiment where plants were exposed for 5 months to two experimental CO2 concentrations (360 and 700 ppm). Both the maximum photosynthetic rate (Pm) and photosynthetic efficiency (alpha) were higher (1.3- and 4.1-fold, respectively) in plants exposed to CO2-enriched conditions. On the other hand, no significant effects of CO2 enrichment on leaf growth rates were observed, probably due to nitrogen limitation as revealed by the low nitrogen content of leaves. The leaf ammonium uptake rate and glutamine synthetase activity were not significantly affected by increased CO2 concentrations. On the other hand, the leaf nitrate uptake rate of plants exposed to CO2-enriched conditions was fourfold lower than the uptake of plants exposed to current CO2 level, suggesting that in the seagrass Z. noltii nitrate is not cotransported with H+ as in terrestrial plants. In contrast, the activity of nitrate reductase was threefold higher in plant leaves grown at high-CO2 concentrations. Our results suggest that the global effects of CO2 on seagrass production may be spatially heterogeneous and depend on the specific nitrogen availability of each system. Under a CO2 increase scenario, the natural levels of nutrients will probably become limiting for Z. noltii. This potential limitation becomes more relevant because the expected positive effect of CO2 increase on nitrate uptake rate was not confirmed.Fundacao para a Ciencia e a Tecnologia [SFRH/BD/21487/2005]; POCI; FSE; COST; EC; EUinfo:eu-repo/semantics/publishedVersio

Aerospace medicine and biology: A continuing bibliography with indexes, supplement 204

This bibliography lists 140 reports, articles, and other documents introduced into the NASA scientific and technical information system in February 1980

Advantages and disadvantages on photosynthesis measurement techniques: A review

Through photosynthesis, green plants and cyanobacteria are able to transfer sunlight energy to molecular reaction centers for conversion into chemical energy with nearly 100% efficiency. Speed is the key as the transfer of the solar energy takes place almost instantaneously such that little energy is wasted as heat. How photosynthesis achieves this near instantaneous energy transfer is a longstanding mystery that may have finally been solved. Measurements of this process are useful in order to understand how it might be controlled and how the phytomonitoring of plant development to increase productivity can be carried out. Techniques in this sense have evolved and nowadays several have been used for this purpose. Thus, the aim of this paper is to present a review of the various methods and principles that have been used in measuring photosynthesis presenting the advantages and disadvantages of various existing measurement methodologies in order to recommend the most appropriate method according to the needs of specific investigations

Carbon allocation and carbon isotope fluxes in the plant-soil-atmosphere continuum: a review

The terrestrial carbon (C) cycle has received increasing interest over the past few decades, however, there is still a lack of understanding of the fate of newly assimilated C allocated within plants and to the soil, stored within ecosystems and lost to the atmosphere. Stable carbon isotope studies can give novel insights into these issues. In this review we provide an overview of an emerging picture of plant-soil-atmosphere C fluxes, as based on C isotope studies, and identify processes determining related C isotope signatures. The first part of the review focuses on isotopic fractionation processes within plants during and after photosynthesis. The second major part elaborates on plant-internal and plant-rhizosphere C allocation patterns at different time scales (diel, seasonal, interannual), including the speed of C transfer and time lags in the coupling of assimilation and respiration, as well as the magnitude and controls of plant-soil C allocation and respiratory fluxes. Plant responses to changing environmental conditions, the functional relationship between the physiological and phenological status of plants and C transfer, and interactions between C, water and nutrient dynamics are discussed. The role of the C counterflow from the rhizosphere to the aboveground parts of the plants, e.g. via CO<sub>2</sub> dissolved in the xylem water or as xylem-transported sugars, is highlighted. The third part is centered around belowground C turnover, focusing especially on above- and belowground litter inputs, soil organic matter formation and turnover, production and loss of dissolved organic C, soil respiration and CO<sub>2</sub> fixation by soil microbes. Furthermore, plant controls on microbial communities and activity via exudates and litter production as well as microbial community effects on C mineralization are reviewed. A further part of the paper is dedicated to physical interactions between soil CO<sub>2</sub> and the soil matrix, such as CO<sub>2</sub> diffusion and dissolution processes within the soil profile. Finally, we highlight state-of-the-art stable isotope methodologies and their latest developments. From the presented evidence we conclude that there exists a tight coupling of physical, chemical and biological processes involved in C cycling and C isotope fluxes in the plant-soil-atmosphere system. Generally, research using information from C isotopes allows an integrated view of the different processes involved. However, complex interactions among the range of processes complicate or currently impede the interpretation of isotopic signals in CO<sub>2</sub> or organic compounds at the plant and ecosystem level. This review tries to identify present knowledge gaps in correctly interpreting carbon stable isotope signals in the plant-soil-atmosphere system and how future research approaches could contribute to closing these gaps

Spring water stress in Scots pine

Water use and net carbon assimilation during spring was examined on Scots pine trees exposed to different soil warming dynamics in the field. Sap flow, needle water potential and net carbon assimilation were measured on trees that were exposed to a wide range of soil temperature regimes caused by manipulating the snow cover on tree-scale soil plots. This made it possible to quantify the sensitivity of water uptake and recovery of gas exchange by Scots pine in the critical transition from winter dormancy to the growing season, which can be influenced by silvicultural practices. A part of the study was to find a tool for estimating the coupled effect of belowground and aboveground climate on transpiration, as well as to adapt this tool to the harsh climate of the boreal forest. Combining the results of field experiments on tree susceptibility to water stress with a physically based SVAT model as well as a model for estimating the recovery of photosynthesis helped to predict spatial and inter-annual variability of snow depths, soil warming, water uptake and net primary productivity during spring within different Scots pine stands across the landscape. This could provide a better basis for a more frostconscious forest management. The studies have confirmed the importance of low soil temperatures in combination with aboveground climate for root water uptake and net carbon assimilation during spring, when soil warming occurs after the start of the growing season. The studies have also confirmed that earlier, controlled laboratory studies on the inhibiting effects of low soil temperature on water relations and gas exchange for seedlings or saplings also hold true on mature trees in the field. The experimental data served well as the basis for model analyses of the interaction between belowground and aboveground conditions on water use and net photosynthesis. The results of the field studies and model analyses suggest that the effect of soil temperature on tree water uptake and net photosynthesis during spring, in conjunction with aboveground conditions, are factors that need to be considered in forest management in areas susceptible to soil frost and low soil temperatures

Surface and Temporal Biosignatures

Recent discoveries of potentially habitable exoplanets have ignited the prospect of spectroscopic investigations of exoplanet surfaces and atmospheres for signs of life. This chapter provides an overview of potential surface and temporal exoplanet biosignatures, reviewing Earth analogues and proposed applications based on observations and models. The vegetation red-edge (VRE) remains the most well-studied surface biosignature. Extensions of the VRE, spectral "edges" produced in part by photosynthetic or nonphotosynthetic pigments, may likewise present potential evidence of life. Polarization signatures have the capacity to discriminate between biotic and abiotic "edge" features in the face of false positives from band-gap generating material. Temporal biosignatures -- modulations in measurable quantities such as gas abundances (e.g., CO2), surface features, or emission of light (e.g., fluorescence, bioluminescence) that can be directly linked to the actions of a biosphere -- are in general less well studied than surface or gaseous biosignatures. However, remote observations of Earth's biosphere nonetheless provide proofs of concept for these techniques and are reviewed here. Surface and temporal biosignatures provide complementary information to gaseous biosignatures, and while likely more challenging to observe, would contribute information inaccessible from study of the time-averaged atmospheric composition alone.Comment: 26 pages, 9 figures, review to appear in Handbook of Exoplanets. Fixed figure conversion error

Effects of elevated CO2 and nutrients on the community metabolism of a Cymodocea nodosa bed

We assessed the combined effects of elevated CO2 and nutrients on the metabolism of a benthic community dominated by the seagrass Cymodocea nodosa (Ucria) Ascherson in a mesocosm experiment. C. nodosa plants and their associated community were exposed to two CO2 levels simulating future (700 ppm, pH 7.84) and current (360 ppm, pH 8.12) conditions, and two nutrient levels (enriched and ambient concentration) in a total of four treatments (-C-N, -C+N, +C-N, +C+N). Net community production (NCP) was estimated from changes in the concentration of dissolved inorganic carbon in the seawater in light incubations using benthic chambers. The variation pattern of NCP with the ordinance was consistent for all treatments. Although differences among treatments were not statistically significant, average NCP values were lowest under CO2 enrichment conditions. NCP was lower at a high CO2 level and ambient nitrogen concentration compared to when nutrient availability was higher, suggesting that the low nutrient availability may modulate the community response to CO2 enrichment. The results obtained suggest that the stimulation of the net community production of C. nodosa by elevated CO2 concentrations may be curtailed by low nutrient availability

Physiological and spectral characterization of leaf demography development on resistant grapevine varieties

openQuesta tesi intende sottolineare l'evoluzione delle caratteristiche fisiologiche e delle proprietà spettrali durante lo sviluppo fogliare della vite. In particolare, lo studio è stato condotto su varietà resistenti di vite note come PIWI. La spettroscopia in viticoltura è stata spesso utilizzata negli ultimi decenni per caratterizzare le proprietà spettrali della vegetazione. La quantità di radiazione che viene riflessa o adsorbita da una pianta è strettamente correlata al contenuto di acqua e al colore delle sue foglie, quindi al loro contenuto di clorofilla, che dipende dal contenuto di azoto. Pertanto, le misure di riflettanza a specifiche lunghezze d'onda sono utili per valutare lo stato fisiologico della foglia e della pianta in generale. Lo studio ha anche preso in considerazione gli aspetti fisiologici legati allo scambio di gas fogliari e alla capacità fotosintetica e come variano durante il ciclo vegetativo della foglia. L'indice Plastochron è stato utilizzato per calcolare l'età biologica delle foglie e l'intero germoglio, per staccare il tempo di calendario e per esprimere questa evoluzione fogliare fisiologica con il tempo biologico.This thesis aims to underline the evolution of physiological characteristics and spectral properties during leaf development on the grapevine. In particular, the study was carried out on resistant grapevine varieties known as PIWI. Spectroscopy in viticulture has often been used during the past decades to characterize the spectral properties of vegetation. The quantity of radiation that is reflected or adsorbed from a plant is closely related to the water content and color of its leaves, thus to their chlorophyll content, which depends on the nitrogen content. Therefore, reflectance measurements at specific wavelengths, are useful in assessing the physiological state of the leaf and the plant in general. The study has also considered the physiological aspects related to leaf gas exchange and photosynthetic capacity and how they vary during the vegetative cycle of the leaf. The Plastochron index was used to calculate the biological age of leaves and the entire sprout, to detach the calendar time, and to express this physiological leaf evolution with the biological time