Levels Of Water Availability Research Articles

Rhizosphere effect alters the soil microbiome composition and C, N transformation in an arid ecosystem

Plants exert positive selection effect on rhizosphere microbes by influencing the nutrient conditions of the rhizosphere microenvironment, thereby changing the soil microbial structure and ecological function. In arid regions, water is the major limiting factor affecting the microbial activity and nutrient conversion. However, the effects of soil water availability on the ecological strategies and the C, N functional metabolism of desert microorganisms remain unclear. We hypothesized that soil water availability and rhizosphere effect might alter the strategy for soil C, N utilization in the arid regions. To test the hypothesis, rhizosphere and bulk soil along a gradient of soil water availability in a dry area of northwestern China were analyzed. The soil samples were collected from Reaumuria songarica, Nitraria tangutorum, and Alhagi sparsifolia and were subjected to metagenomic sequencing with a HiSeq system. The relative abundance of Gemmatimonas and Gemmatirosa increased with the increased soil water content, whereas the relative abundance of Microvirga and Nocardioides was decreased. The relative abundance of Azospirillum and Bradyrhizobium did not change with the water content as these microbial communities use limited-water, are drought-tolerant, and use inert strategies to adapt to different levels of water availability. The genes encoding ribulose 1,5-bisphosphate carboxylase/oxygenase (RuBisCO) were more abundantly expressed in low water than in high to medium water availability (P < 0.05). The abundance of nitrate reduction genes decreased significantly with the increase in soil water availability, whereas that of denitrification genes increased. The relative abundance of the dissimilatory nitrate reduction process in the rhizosphere soil (44.83%) was significantly higher than that in the bulk soil (39.21%). It can be inferred that soil microorganisms adopt the nitrogen utilization strategy by increasing the ammonium nitrogen to mitigate reduced water availability and provide a nitrogen-rich environment to plant roots.

Does water availability affect the critical N dilution curves in crops? A case study for maize, wheat, and tall fescue crops

Previous studies reported an effect of water deficit on crop nitrogen (N) demand but the statistical significance of this effect is unclear and the physiological mechanism explaining this effect remains poorly understood. The specific aims of this review are (i) assess whether the parameters of the N dilution curve are significantly influenced by the level of water availability and (ii) provide a synthesis of the plausible physiological mechanisms involved on changes in N dilution. To address the first goal, several datasets assessing the effects of water availability on N status of maize (Zea mays L.), wheat (Triticum aestivum L.), and tall fescue (Lolium arundinaceum (Schreb.) Darbysh.) were combined and then used to fit N dilution curves with a Bayesian statistical approach. Concerning the second objective, we investigate two possible mechanisms, namely a modification in water soluble carbohydrates (WSCs) and an effect on plant architecture and morphology impacting the allometry between structural and metabolic compartment. Our re-analysis of published data for tall fescue, wheat, and maize reveals no conclusive evidence supporting an effect of water availability effect on the N dilution curve. In addition, we show that WSCs accumulation under water deficit condition is unlikely to be accompanied by N-rich soluble compounds, and that a reduction of water availability has limited effect on the allometry of plant mass allocation. Lastly, our conclusion provides new insights on the use of a common critical N dilution curve (one model across water levels) for estimating the crop N status where both water (under no extreme deficiency) and N stresses are operating in order to separate direct effect of water availability from its indirect effect on crop N nutrition status.

Assessing the impacts of irrigation termination periods on cotton productivity under strategic deficit irrigation regimes

Determining optimum irrigation termination periods for cotton (Gossypium hirsutum L.) is crucial for efficient utilization and conservation of finite groundwater resources of the Ogallala Aquifer in the Texas High Plains (THP) region. The goal of this study was to suggest optimum irrigation termination periods for different Evapotranspiration (ET) replacement-based irrigation strategies to optimize cotton yield and irrigation water use efficiency (IWUE) using the CROPGRO-Cotton model. We re-evaluated a previously evaluated CROPGRO-Cotton model using updated yield and in-season physiological data from 2017 to 2019 growing seasons from an IWUE experiment at Halfway, TX. The re-evaluated model was then used to study the effects of combinations of irrigation termination periods (between August 15 and September 30) and deficit/excess irrigation strategies (55%-115% ET-replacement) under dry, normal and wet years using weather data from 1978 to 2019. The 85% ET-replacement strategy was found ideal for optimizing irrigation water use and cotton yield, and the optimum irrigation termination period for this strategy was found to be the first week of September during dry and normal years, and the last week of August during wet years. Irrigation termination periods suggested in this study are useful for optimizing cotton production and IWUE under different levels of irrigation water availability.

Using leaf-based hyperspectral reflectance for genotype classification within a soybean germplasm collection assessed under different levels of water availability

ABSTRACT Because of the major international issue of intellectual property rights over seed technology, time-efficient methodologies that could characterize and monitor soybean genotypes are increasingly needed as they contribute to royalty collection and better management of seed genetics, leading to more efficient production strategies. This research aims at developing models capable of spectrally classifying soybean genotypes, at leaf scale, under different levels of water availability. Leaf reflectance spectra were collected using the Fieldspec 3 Jr. spectroradiometer, a hyperspectral proximal sensor. Two experiments were conducted at Embrapa Soja (Brazilian Agricultural Research Corporation). Experiment I was carried out in a plant growth chamber, using 12 soybean genotypes with different tolerance levels to drought, submitted to irrigation and water deficit treatments, where 214 spectral samples were collected. Experiment II was conducted in a greenhouse, using 164 soybean genotypes (from 15 different countries) with different responses to drought, submitted to irrigation and water deficit treatments, where 6,046 spectral samples were collected. Principal component analysis (PCA) was used to explore the qualitative spectral differences among the evaluated genotypes within each spectral dataset, and the stepwise procedure was carried out to select the wavelengths that best discriminate the soybean genotypes. Linear discriminant analysis (LDA) was used to obtain a model of classification of each leaf-based reflectance spectrum for each soybean genotype by its spectral behaviour. The acquired leaf reflectance was similar among soybean genotypes. The PCA explained over 96% of the spectral variance in the first three principal components, and the stepwise procedure selected 70 and 410 spectral bands in each dataset. In Experiment I, LDA presented an accuracy of 100%. In Experiment II, the LDA classified 149 genotypes with an accuracy of over 90%. The obtained results demonstrate the great potential of the spectral classification of soybean genotypes at leaf scale, regardless of the water status of the plants.

Biomass allocation of Vincetoxicum rossicum and V. nigrum in contrasting competitive environments.

Understanding how drought and biomass allocation patterns influence competitive ability can help identify traits related to invasiveness and guide management. Vincetoxicum nigrum and V. rossicum are increasingly problematic herbaceous perennial vines in the northeastern United States and southeastern Canada. Using a greenhouse experiment, we investigated how biomass allocation and competition intensity of Vincetoxicum spp. responded to four competitive regimes at two levels of soil water availability in the presence of conspecific or congeneric neighbors. Soil moisture was the most important influence on growth and biomass allocation. Vincetoxicum nigrum had a greater capacity for growth and reproduction than V. rossicum, especially under drought. Drought reduced the probability of reproduction for V. rossicum. Vincetoxicum rossicum had a higher root-to-shoot ratio than V. nigrum under adequate soil moisture. This difference more than doubled under drought. Under interspecific competition, V. nigrum maximized its biomass, while V. rossicum limited aboveground growth and reproduction. Root-only competition increased shoot and root biomass relative to shoot-only competition. The effects of root and shoot competition were additive under interspecific competition, but interacted under intraspecific competition (negative interaction under drought and positive interaction under sufficient soil moisture). Management strategies targeting mixed populations of V. rossicum and V. nigrum are most important under ample water availability. Under drought conditions, strategies focused on V. nigrum should effectively limit Vincetoxicum growth and seed reproduction. Phenotypic plasticity and the positive competition intensity associated with drought in monocultures may contribute to drought resistance in these invasive species.

Ontogenetic trait shifts: Seedlings display high trait variability during early stages of development

AbstractCharacterizing variation in plant functional traits is often key to understanding community‐level processes and predicting ecosystem responses to environmental change. Trait‐based ecology has focused on interspecific trait variation, but sources and consequences of within‐species ontogenetic trait variation, particularly during early stages of development, remain understudied.Using a manipulative greenhouse experiment, we investigated trait variation during early stages of seedling development in seven dominant perennial plant species in the western United States. We examined variability in key trait values (i.e. SLA, root:shoot ratio (RSR), specific root length (SRL) and root dry matter content (RDMC)) of 20‐ to 62‐day‐old seedlings grown under low and high levels of water availability. We also compared these to compiled trait databases to assess how representative these readily available data sources are of seedling trait values.Early seedling trait values shifted greatly during early stages of development and generally differed from average plant trait database values. Trait shifts were greatest in forbs versus grasses. Overall, observed trait shifts suggested a transition from fast‐growing resource acquisitional strategies towards more slow‐growing conservative strategies over time. For example, seedling SLA decreased while RSR and RDMC increased over time.That seedling trait values aconsistently differed from trait database values indicates that plant trait database values may be poor predictors of seedling trait values. Such mismatches in species trait information could result in inaccurate predictions of community assembly outcomes or incongruities between seedling traits and environmental filters experienced by seedlings during early stages of recruitment in applied settings.We suggest that additional work is needed to characterize intraspecific trait variation across plant ontogeny, and that this information should be incorporated into studies ranging from understanding early plant growth and survival to evaluating the outcomes of ecological restoration.A freePlain Language Summarycan be found within the Supporting Information of this article.

A laboratory approach on the combined effects of granite bioreceptivity and parameters modified by climate change on the development of subaerial biofilms on cultural heritage

Conservation of cultural heritage buildings and monuments may be negatively affected by the impact of climate change on substrates and colonizing microorganisms. In this study, four types of commercial granite, in which the bioreceptivity ranged from very low to very high, were inoculated with a multispecies microbial culture and exposed to different temperatures (18 and 24 °C) and levels of water availability (1 day, 3 days and 7 days of water availability/week) to simulate different climatic conditions. The effects on biofilm formation of the interactions between the substrate bioreceptivity and the environmental parameters were investigated. Biofilm growth and photosynthetic efficiency were monitored over 42 days by pulse-amplitude modulated (PAM) fluorometry and spectrophotometric colour measurement. The primary bioreceptivity of the granite was a determining factor in the organisms' capacity to attach to the substrate and interacted through the experiment with the climatic conditions by modifying the development of the microorganisms. Water availability was a limiting factor for the colonizing microorganisms, in terms of both growth and photosynthetic efficiency. At the higher temperature, metabolic reactions were enhanced under water restriction (but not under maximum water availability) and the microbial ecology was altered, leading to a higher proportion of cyanobacteria relative to algae.

Establishment of Cryptostegia madagascariensis in the semiarid: what is the role of abiotic factors in germination and initial growth?

Studies on seed germination and seedling development in different environmental conditions help to understand the ability of exotic species to colonize new environments. Cryptostegia madagascariensis is an exotic invasive species in the semiarid Caatinga Phytogeographical Domain, in the northeastern region of Brazil. In this study, was evaluate how the abiotic factors interfere in germination and the impacts of a water deficit in the initial growth of seedlings. During germination, the seeds were exposed to different temperatures (constant and alternating) combined with two light conditions (white and dark light). In germination, we also evaluated the effects of water and saline stress. In initial growth, the seedlings were submitted to four levels of water availability (100%, 70%, 40% and 10% of field capacity). The milder (20 at 30°C) and alternate temperatures studied provided greater germination four days after sowing, independent of light. High temperatures (35°C) are a limiting factor for germination, as well as water and saline stress (&gt;2 MPa). The water deficit reduces the growth of the seedlings, but these showed morphological adaptations to the different treatments. However, lower levels of water reduced its invading potential. Therefore, factors such as high temperature (&gt; 30° C), saline and water stress, reduce its germination potential and the reduction of water availability affects its growth, but not its survival.

Seasonal home-range size of the white-tailed deer, Odocoileus virginianus thomasi, in a tropical wetland of southeastern Mexico

White-tailed deer, Odocoileus virginianus , home range size (HR) is one of the most studied aspects of its biology. However, in the southern portion of its distribution, information about its HR is scarce, limiting the capacity for management of the species. To understand the effect of sex and seasonality on the HR of white-tailed deer in a tropical area, we radiotracked 11 adult white-tailed deer (7 females and 4 males) from 2016 to 2019 in a tropical wetland of western Campeche, Mexico. We found female HR to vary from 12.67 ha (±3.52) in the early dry season to 21.57 ha (±18.14) during the late dry season, and from 37.31 ha (±16.93) for the late dry season to 90.16 ha (±72.64) during the rainy season in males. We did not find differences of HR among seasons. However, we found seasonal differences when we tested separately the HR for females and males, showing that female HR is similar among seasons, whereas males had smaller HR during the dry seasons than during the rainy season. Our results indicate that water availability and flooding levels could affect the HR and configuration of the white-tailed deer in the study area.

Assessment of irrigation water interval on maize in dryland in central sulawesi

Dryland agriculture has many problems, one of which is the limited level of water availability. The water supply interval is able to use water efficiently with the maximum possible yield potential. This study aims to determine the time of giving water that can give optimum results in maize cultivation in dry climates. The research was conducted at the Sidondo III Agricultural Technology Research and Assessment Installation, Sigi Biromaru District, Sigi Regency, Central Sulawesi. The activity was carried out from March to July 2019. The method used was Randomized Block Design using Bima 15 Variety with four water treatment intervals (Control, 8 days, 14 days and 18 days) and each was repeated 3 (three) times. Interval treatment of giving water every 8 days gave better growth and yield compared to other water treatment intervals, namely each 114.67 cm plant height, 10.40 strands number of leaves, 1.51 cm stem diameter, 16.70 cm cob length, 4.36 cm cob diameter, 38 seeds each row, 171.33 grams of 5 cob weight sample, 26. 86 grams weight of jenggel and 6.63 tons / ha yield.

Reproductive strategies involving biomass allocation, reproductive phenology and seed production in two Asteraceae herbs growing in karst soil varying in depth and water availability

Shallow soil with low water availability, poor nutrition, and limited living space is the key limiting factor of plant growth and reproduction in vulnerable karst regions. As pioneers adapted to these areas, little is known about the reproductive responses of annual herbs to these limited soil resources. In this study, we, therefore, investigated the reproductive strategies (“fight or flight”) of two annual Asteraceae herbs (Xanthium sibiricum and Bidens pilosa) growing in the harsh karst soil environment, by comprehensively considering biomass allocation, reproductive phenology, and seed production. X. sibiricum and B. pilosa were grown under three soil depths and three water availability levels in a full two-way randomized block design, then biomass allocation, initial flowering time, fruiting stage, life span and seed number and mass were examined. In X. sibiricum, reproductive allocation decreased with decreasing water availability, soil depth, and water availability + soil depth. Meanwhile, the initial flowering time, fruiting stage and life span were all delayed with moderate decreases in resources. However, in B. pilosa, reproductive allocation increased with decreasing soil resources, while initial flowering time, fruiting stage and life span remained unchanged under moderate resource decline. Under severe resource decline, both species showed a reduction in fruiting stage and life span. These results support the hypothesis that X. sibiricum tends to adopt a “fight” reproductive strategy in response to declining resources via changes in biomass allocation, reproductive phenology and seed production. In contrast, B. pilosa tends to adopt a “flight” strategy in terms of biomass allocation, while maintaining a relatively stable reproductive phenology and seed size to cope with the harsh living conditions. However, neither species coped well under severe declines in water availability, nutrition and living space. These findings help our understanding of how herbaceous plants can adjust their reproductive strategies to support their regeneration in harsh karst soil environments.

Yield Prediction in Soybean Crop Grown under Different Levels of Water Availability Using Reflectance Spectroscopy and Partial Least Squares Regression

Soybean grain yield has regularly been impaired by drought periods, and the future climatic scenarios for soybean production might drastically impact yields worldwide. In this context, the knowledge of soybean yield is extremely important to subsidize government and corporative decisions over technical issues. This paper aimed to predict grain yield in soybean crop grown under different levels of water availability using reflectance spectroscopy and partial least square regression (PLSR). Field experiments were undertaken at Embrapa Soja (Brazilian Agricultural Research Corporation) in the 2016/2017, 2017/2018 and 2018/2019 cropping seasons. The data collected were analyzed following a split plot model in a randomized complete block design, with four blocks. The following water conditions were distributed in the field plots: irrigated (IRR), non-irrigated (NIRR) and water deficit induced at the vegetative (WDV) and reproductive stages (WDR) using rainout shelters. Soybean genotypes with different responses to water deficit were distributed in the subplots. Soil moisture and weather data were monitored daily. A total of 7216 leaf reflectance (from 400 to 2500 nm, measured by the FieldSpec 3 Jr spectroradiometer) was collected at 24 days in the three cropping seasons. The PLSR (p ≤ 0.05) was performed to predict soybean grain yield by its leaf-based reflectance spectroscopy. The results demonstrated the highest accuracy in soybean grain yield prediction at the R5 phenological stage, corresponding to the period when grains are being formed (R2 ranging from 0.731 to 0.924 and the RMSE from 334 to 403 kg ha−1—7.77 to 11.33%). Analyzing the three cropping seasons into a single PLSR model at R5 stage, R2 equal to 0.775, 0.730 and 0.688 were obtained at the calibration, cross-validation and external validation stages, with RMSE lower than 634 kg ha−1 (13.34%). The PLSR demonstrated higher accuracy in plants submitted to water deficit both at the vegetative and reproductive periods in comparison to plants under natural rainfall or irrigation.

Impact of relative humidity and water availability on the life history of the predatory mite Amblyseius swirskii

The predatory mite Amblyseius swirskii (Athias-Henriot) (Acari: Phytoseiidae) is currently used as an efficient biological control agent of thrips, whiteflies and spider mites, which are economically damaging pests of ornamental plants and vegetable crops grown in greenhouses and fields worldwide. Currently, the effects of relative humidity (RH) and water availability on the optimal growth of A. swirskii are unknown. Here, we test the combined effects of different levels of RH (33%, 53%, 73% and 92%) and water availability on the development and reproduction of male and female A. swirskii feeding on the dried fruit mite, Carpoglyphus lactis (Linnaeus). While eggs failed to hatch at 33% RH, the survival rates of the immature stages at ≥ 53% RH increased solely in response to water availability and not due to changes in RH. Regarding growth and development, low RH extended the egg–adult duration and pre-oviposition period. We also found that the negative effects of low RH on fecundity were partially or completely eliminated when drinking water was available. For the life table parameters, the highest values of net reproductive rate (R0) and intrinsic rate of natural increase (r) were achieved at the highest RH and when drinking water was available. Overall, water availability mitigated the negative effect of low RH on female reproduction, and female development was more sensitive to water availability than male development. Lastly, a comparison of similar research on A. swirskii suggested that water availability and RH are more influential on r than food source or temperature.

Characterization of Performance 12 Superior Lines of Upland Rice Planted in Two Environmental Condition

The development of upland rice cultivars that could also adapt to lowland will be needed to anticipate climate change effects. The identification of several characters and their performance needs to be studied. Morpho-agronomic characters are divided into qualitative and quantitative character. The research aimed to identify several qualitative and quantitative characters’ changes to obtain adaptive information lines in both environments. The experiment was conducted in a greenhouse from January until June 2020. As many as 12 promising upland rice lines were used as the source of genetic materials. There are two types of growing environment simulated as a treatment: (1) lowland and (2) upland; each treatment line was repeated three times. Data were analyzed using the PAST 3.25 program. Clustering analysis was performed using the UPGMA algorithm and the euclidean distance, and quantitative data were also analyzed using a comparison of relative values. The results on qualitative characters show the color type does not change even in different environments, but there is a gradient of color sharpness in several characters. Some anthocyanin-related color characters become more concentrated in upland environments than lowland and chlorophyll-related colors are vice versa. Based on the color character, the L8 line is more stable in both environments than the other lines, and the L12 line had the best vigor in both environments. Biplots of eight color characters in lowland and dry conditions indicate that the lines are divided into two groups. The principal analysis (PCA) on lowland and upland of obtained two and three PCs, with eigenvalues > 1, and it is mean explained that the diversity index of examined material was 73.1% and 87%. Most of the lines show that the relative changes in qualitative and quantitative characters in two environments, except the L5 line, are more stable. Biplot-PCA clustering on 11 quantitative characters in a lowland and dry environment formed small clusters with a small number of lines in them. The clustering analysis between qualitative and quantitative characters in 12 upland rice lines did not have the same illustration. This study proves that different levels of water availability will affect several color gradient and several quantitative characters. It seems that although upland rice is grown on dry land, plant growth will be better if planted in lowland environment.

EFECTO FISIOLÓGICO DE LA DISPONIBILIDAD DE AGUA Y NITRÓGENO EN PLANTAS DE GUAYABA

&lt;p&gt;&lt;strong&gt;Background:&lt;/strong&gt; The water deficit and the low availability of nutrients are factors that limit the growth and productivity of cultivated plants. &lt;strong&gt;Objective:&lt;/strong&gt; To evaluate the effect of nitrogen and water availability on growth, chlorophyll concentration and photosynthetic efficiency of guava plants (&lt;em&gt;Psidium guajava&lt;/em&gt; L. var. cuban red dwarf). &lt;strong&gt;Methodology&lt;/strong&gt;: A completely randomized experiment with bifactorial arrangement was designed under greenhouse conditions. Factor A was composed by two levels of nitrogen availability (N1: 1.0 g of nitrogen per plant, N0: no nitrogen application) and factor B by two levels of water availability (A&lt;sub&gt;400&lt;/sub&gt;: 400 mL of water every three days and A&lt;sub&gt;200&lt;/sub&gt;: 200 mL of water every three days). &lt;strong&gt;Results:&lt;/strong&gt; Indicators of photosynthetic structure gain (leaves and branches per plant) were more sensitive to water and nitrogen availability from the early stages of plant development, showing the highest values in treatments with higher nitrogen supply, regardless of water availability. Stem growth was higher in the treatments with higher nitrogen and water supply at 80 ddt, similar to that observed in leaf growth and branch emission, regardless of water availability. &lt;strong&gt;Implications:&lt;/strong&gt; The findings found provide new knowledge about the plasticity of cuban red dwarf guava to the conditions of water and nitrogen availability contrasting with the conditions of the experimental site. &lt;strong&gt;Conclusions:&lt;/strong&gt; Guava plants respond to nitrogen and water limitations in the substrate, increasing root growth as a survival strategy in environments with scarce soil resources, while floods with higher water and nitrogen availability increase their assimilation capacity, proportionally to the chlorophyll&lt;strong&gt; &lt;/strong&gt;content.&lt;/p&gt;

Primacy of plants in driving the response of arthropod communities to drought

Drought threatens arthropod communities worldwide. Water limitation affects the quantity and quality of plants available to herbivores as food, and can also affect higher trophic-level consumers through variability in prey quality and reduced availability of suitable habitats. Our study assessed the response of an arthropod community to water limited wheat (Triticum aestivum L.) in a field setting. We used rainout shelters to exclude precipitation, irrigated raised bed plots to create three levels of water availability, and monitored arthropod community development over 8weeks. First, we compared arthropod communities in habitats with different levels of water limitation and found that community composition was reliant on the magnitude of the water stress. This difference was largely due to the loss of piercing-sucking herbivores and predators in high-stress environments. Next, we focused on aphids and their natural enemies to investigate the underlying mechanisms driving community responses using structural equation modeling (SEM). Aphid abundance was negatively affected by water limitation, and this response was primarily associated with stress-induced plant physiological changes and not plant biomass or natural enemy abundance. Natural enemy abundance was also reduced in water-limited habitats, but natural enemies responded to plant biomass and not prey availability. These effects were exacerbated as water stress increased. The absence of natural enemy effects on aphids indicates that top-down predation effects were dampened by strong bottom-up effects of plant water limitation. This study revealed the importance of considering water stress intensity when predicting outcomes of droughts for arthropod communities.

Differential Changes in D1 Protein Content and Quantum Yield of Wild and Cultivated Barley Genotypes Caused by Moderate and Severe Drought Stress in Relation to Oxidative Stress

The aim of this study was to investigate the effects of drought stress on oxidative damage and efficiency of PSII photochemistry in barley and compare the varietal response of different genotypes including Yusof (tolerant), Moroc9-75 (sensitive), and wild barley (HS) to drought. Plants were subjected to different levels of soil water availability including control, moderate, and severe drought stress. Exposure to drought stress led to decrease in leaf water potential, biomass production, and stomatal conductance (gs) in all genotypes. Drought induced an increase in H2O2 content followed by increase in malondialdehyde (MDA) as a final result of lipid peroxidation. Drought stress also resulted in reduction of D1 protein content in all genotypes and decreased the maximal quantum yield of PSII photochemistry (FV/FM). These parameters were more affected in Moroc9-75 cultivar by drought stress compare to Yusof and HS genotype. Based on our results, drought-induced reactive oxygen species may decrease PSII photochemistry either through peroxidation of thylakoid membranes or interfering with D1 protein synthesis, necessary for proper function of PSII.

Classification of Soybean Genotypes Assessed Under Different Water Availability and at Different Phenological Stages Using Leaf-Based Hyperspectral Reflectance

Monitoring of soybean genotypes is important because of intellectual property over seed technology, better management over seed genetics, and more efficient strategies for its agricultural production process. This paper aims at spectrally classifying soybean genotypes submitted to diverse water availability levels at different phenological stages using leaf-based hyperspectral reflectance. Leaf reflectance spectra were collected using a hyperspectral proximal sensor. Two experiments were conducted as field trials: one experiment was at Embrapa Soja in the 2016/2017, 2017/2018, and 2018/2019 cropping seasons, where ten soybean genotypes were grown under four water conditions; and another experiment was in the experimental farm of Unoeste University in the 2018/2019 cropping season, where nine soybean genotypes were evaluated. The spectral data collected was divided into nine spectral datasets, comprising single and multiple cropping seasons (from 2016 to 2019), and two contrasting crop-growing environments. Principal component analysis, applied as an indicator of the explained variance of the reflectance spectra among genotypes within each spectral dataset, explained over 94% of the spectral variance in the first three principal components. Linear discriminant analysis, used to obtain a model of classification of each reflectance spectra of soybean leaves into each soybean genotype, achieved accuracy between 61% and 100% in the calibration procedure and between 50% and 100% in the validation procedure. Misclassification was observed only between genotypes from the same genetic background. The results demonstrated the great potential of the spectral classification of soybean genotypes at leaf-scale, regardless of the phenological stages or water status to which plants were submitted.

Water restriction in different phenological stages and increased temperature affect cowpea production

ABSTRACT Water deficit and high temperatures are abiotic factors that most limit plant growth and development. However, its effects depend on crop development stage and on stress duration and intensity. Thus, the objective of was to evaluate the development of cowpea subjected to water restriction in different phenological stages and to increase in air temperature. The experiment was conducted with the cultivar ‘Carijó’, in growth chambers, in a 4 x 3 x 2 factorial arrangement, corresponding to levels of water availability (25, 50, 75, and 100%,), phenological stages (vegetative, flowering and pod filling) and temperature regimes (T°1: 20-26-33 °C e T°2: 24.8-30.8-37.8 °C), respectively. Reduction of water availability in the vegetative and flowering stages caused decrease in grain production. The percentage of aborted flowers was higher in plants maintained under an increased temperature of +4.8 °C, with consequent reduction in grain production. Higher water availability values favored shoot and root dry mass production. Increase of 4.8 °C did not affect shoot and root dry mass but reduced water use efficiency by about 83%. The highest enzymatic activities of CAT, GPX and SOD were found in plants subjected to the temperature of +4.8 °C. Only APX showed lower enzymatic activity with increasing temperature. The cv. ‘Carijó’ is more sensitive to the 4.8 °C increase in air temperature than to water deficits.

Ground Water Level Prediction

The groundwater is one of the biggest asset. The continuous decline of underground water is one of the crucial factors that affect the development of economy and society. Based on the availability the water is to be exploited. The population growth and emerging climate change lead to water scarcity problem. This would have increased the demand for ground water. But the groundwater is not distributed equally. In our proposed system we state the annual ground water availability for future use. It can be classified by machine learning algorithms such as logistic regression, random forest and decision tree. The input variables used for modelling is based on the recharge of water and usage of water in various season. The regression task needs less training data set and can achieve good performance. The aim of this paper is to compare and analyse the machine learning algorithm for ground water level along with their accuracy. In this paper the machine learning algorithm is used to classify and detect the ground water availability levels in India.