Water Availability Conditions Research Articles

Preface to the proceedings of Halophiles 2013.

Halophiles are organisms, and their viruses, adapted to thriving and reproducing in high salt concentrations, representatives of which can be found in all domains of life. To flourish in these environments, an individual must overcome many obstacles including high osmotic pressure, low water availability, high and low pH conditions, high temperatures, and high cell densities that enforce stiff competition for limited resources due to the low solubility of gasses and other nutrients. Therefore, all halophiles can be considered poly-extremophiles. These interesting life forms do not cause infectious diseases or cancer, impact human lifestyles or infect our food supply. So why study them? Often halophiles are studied because the salty environment is a model system for uncovering basic principles of microbial life. This extreme environment selects against any organism not able to cope with high salt, which reduces the overall community structure and function. The expectation is that this decrease in complexity allows for more easily achieved insights into fundamental microbial adaptations, and ecological, biogeochemical and evolutionary processes. Because the extreme hypersaline environments are limited to only microbial life, the habitat is analogous to that which existed on Earth before the Cambrian Explosion. Thus investigations of hypersaline habitats can deliver insight into the longest epoch of life. Modern microbial mats growing in hypersaline habitats are similar in structure to ancient stromatolites found in the Precambrian fossil record. Related to this is the search for life in the cosmos: the long period of dominant microbial life on Earth suggests a higher likelihood of finding microbial life on another world than finding advanced life, sentient beings, or even trees. Additionally, the adaptations required for life in high salt can produce enzymes that are interesting for biotechnology, industrial processes, and bioremediation. Every 3 years since the late 1970s halophile researchers who focus on microbial life in hypersaline environments have gathered to present their latest exciting research to like-minded souls. This eBook is a compendium of research written by many of the presenters at Halophiles 2013, the international congress held at the University of Connecticut in Storrs, CT (to view all of the conference oral and poster presentation abstracts, please visit https://www.regonline.com/custImages/250000/250066/Halophiles2013Program_final.pdf). Its range of subject matter is extensive reflecting the 4-day event, and the breadth of research interests. To address this diversity of topics, the chapters are arranged into slightly narrower areas of research interests, but even within these defined partitions the reader will find a wide range of interesting research. Here, we explore the world of halophiles.

Maize water use efficiency and evapotranspiration response to N supply under contrasting soil water availability

Water use efficiency (WUEg), the quotient between grain yield and crop evapotranspiration (ET), might be increased in maize crops (Zea mays L.) due to N supply. Most research has focused on understanding grain yield response to N supply; so there is little and contradictory information on the influence of N supply on WUEg in water limited environments and on ET response to N supply under contrasting water availability. The objectives of our research were to elucidate whether N supply affects WUEg in water limited environments; and to clarify the expected response to N supply of maize ET and its components under contrasting soil water availability. Maize crops were grown at Balcarce, Argentina during three seasons. Treatments included two water regimes (i.e. rain-fed and irrigated) and two rates of N (i.e. 120kgNha−1 or non-fertilized). Measurements included (i) soil water content and intercepted photosynthetically active radiation (iPAR) during the whole crop season, and (ii) grain yield and shoot dry matter at physiological maturity. Crop ET was calculated by means of a water balance and soil evaporation was estimated by means of micro-lysimeters. Our results show that N supply did not influence WUEg in water limited environments; but N supply significantly increased ET (2–8%) under all water availability conditions. Maize seasonal ET increments were closely related to the improvement of seasonal iPAR in non-water limited environments, but not in water limited environments. In non-water limited environments, ET response to N supply was mediated by the concomitant effects of iPAR increments on increasing transpiration while reducing evaporation. In water limited environments, ET slightly increased in response to iPAR increments due to N supply. The low ET increment in water limited environments with frequent low superficial soil water content (i.e. ≤2mmcm−1) was probably not influenced by reductions in evaporation (E); but associated with stomata closure in response to water deficiencies. This is consistent with the fact that N supply did not promote improvements in radiation use efficiency for biomass production (RUEb) in these environments.

GAS EXCHANGE AND CARBOHYDRATE PARTITIONING IN COFFEE SEEDLINGS UNDER WATERLOGGING

Irrigation has enhanced coffee production in several regions of Brazil. However, with the increase in irrigated crop areas, problems related to the frequent and poorly planned usage of irrigation may arise. Since there are few studies related to the physiological alterations in coffee plants exposed to water excess, we evaluated the effects of waterlogging on metabolism and partitioning of carbohydrates, levels of photosynthetic pigments and gas exchange in seedlings of two commercial coffee cultivars (Mundo Novo and Catuaí). After acclimation, seedlings with eight pairs of fully expanded leaves were cultivated under three water availability conditions: field capacity, intermittent waterlogging and continuous waterlogging. Gas exchange and the levels of chlorophyll, carotenoids and carbohydrates were evaluated during the five months after the beginning of the treatments. Waterlogging reduced the rates of photosynthesis and transpiration, leading to lower activity of the carboxylative step of photosynthesis and culminating in the reduction of carbohydrate partitioning in coffee seedlings. Although many physiological parameters were affected by waterlogging, the cultivars in our study survived for five months under stressful conditions.

Ecophysiology of two tropical species in an abandoned eucalyptus plantation: effect of plant litter removal and seasonality

The effect of the removal of plant litter on photosynthetic variables (gas exchanges, chlorophyll a fluorescence, and content of photosynthetic pigments) of the tropical species Xylopia sericea A. St.-Hil. and Siparuna guianensis Aubl. was evaluated in an abandoned plantation of eucalyptus (Corymbia citriodora (Hook.) K.D. Hill & L.A.S. Johnson (Myrtaceae)). The study was conducted at the Uniao Biological Reserve, Rio de Janeiro State, Brazil during the rainy and dry periods, after five years of litter removal. The removal of plant litter did not influence the ecophysiological responses of the species. There was however significant seasonal variation. During the dry period, intercellular CO2 concentration (Ci), transpiration (E), and stomatal conductance (gs) were decreased, while intrinsic efficiency of water use (IWUE), non-photochemical quenching (NPQ), and carotenoid values increased, suggesting a protective strategy against stress. Nevertheless, the values for Fv/Fm (maximum quantum efficiency) and Fm/Fo (ratio of fluorescence yields for open and closed states) indicated that even during the dry period there was no reduction in photochemical activity in these species. Only S. guianensis exhibited a reduced net photosynthetic rate (A) during the dry period. The data indicated that X. sericea was photosynthetically more efficient under conditions of low water availability and that a 5-year period of plant litter removal failed to produce differences in ecophysiological processes in the species analyzed.

Inheritance of reversions to male fertility in male-sterile sorghum hybrids with 9E male-sterile cytoplasm induced by environmental conditions

Heritable phenotypic alterations occurring during plant ontogenesis under the influence of environmental factors are among the most intriguing genetic phenomena. It was found that male-sterile sorghum hybrids in the 9E cytoplasm from the F1 and F2 generations, which were obtained by crossing CMS lines with different fertile lines grown in field conditions, when they have been transferred to greenhouse produce fertile tillers. Lines created by the self-pollination of revertant tillers exhibit complete male fertility upon cultivation under various environments (in the field, “dry plot,” “irrigated plot”). In a number of test-crosses of revertants to CMS lines in the 9E cytoplasm, restoration of male fertility in F1 hybrids was found, indicating that revertants possess functional fertility-restoring genes. A high positive correlation was found between the fertility level of the test-cross hybrids and the hydrothermal coefficient (the ratio of the sum of precipitation to the sum of temperatures) during the booting stage and pollen maturation (r = 0.75…0.91; P < 0.01), suggesting that a high level of plant water availability is needed for the expression of fertility-restoring genes of revertants. These data show that the fertility-restoring genes for the 9E cytoplasm are dominant in conditions of high water availability and recessive in drought conditions; reversions to male fertility are due to up-regulation of fertility-restoring genes by a high level of water availability. Comparative MSAP-analysis of DNA of malesterile and male-fertile test-cross hybrids using HpaII/MspI restrictases and primers to polygalacturonase gene ADPG2, which is required for cell separation during reproductive development, and gene MYB46, the transcription factor regulating secondary wall biosynthesis, revealed differences in the number and the length of amplified fragments. Changes in the methylation of these genes in conditions of drought stress are apparently the reason for male sterility of sorghum hybrids in the 9E cytoplasm. These data demonstrate that methylation of nuclear genes in sterility-inducing cytoplasm may be one of mechanisms causing the CMS phenomenon.

Consideration of Water Productivity for Farm Water Management in Different Conditions of Water Availability for Dominant Summer Crops

ABSTRACT- Efficient use of irrigation water for summer crops should be considered seriously due to rare occurrence of precipitation in summer. This research was focused on the assessment of water use efficiency for dominant crops of summer cropping pattern in the study area (i.e., maize and rice) via considering water productivity (WP) with different water management scenarios at farm level at different climatic conditions. Results indicated that in most cases the maximum WP was not occurred at full irrigation scenario. With increasing irrigation application efficiency (Ea), WP increased and the maximum WP shifted toward higher water reduction fraction (WRF). For maize, in deficit irrigation scheduling (DIS) methods with full irrigation at flowering stage, more deficit irrigation application was economically acceptable. For rice, with increasing Ea and WRF, WP increased and deficit irrigation at different growth stages was economically acceptable. Considering the real cost of water, economic water productivity ratio (EWPR) decreased greatly and in surface irrigation system, Ea should be increased and high WRF should be avoided (WRF should be lower than 0.4). In solid-set sprinkler system, EWPR increased with increasing Ea and application of WRF higher than 0.2 (0.2-0.6 for maize) was acceptable. Tape irrigation of maize was acceptable only for WRF less than 0.2; also, 0.2-0.4 was acceptable for WRF by decreasing the Ea.

Genome-wide association mapping of agronomic traits and carbon isotope discrimination in a worldwide germplasm collection of spring wheat using SNP markers

Association mapping has been proposed to identify polymorphisms involved in phenotypic variations and may prove useful in identifying interesting alleles for breeding purposes. Using this approach, a total of 382 cultivars and advanced lines of spring wheat obtained from three breeding programs (Chile, Uruguay and CIMMYT) were evaluated for plant height (PH), kernels per spike (KS), 1,000 kernel weight (TKW), grain yield and carbon isotope discrimination (Δ13C) and tested for genotyping-by-sequencing-derived SNP markers across the hexaploid wheat genome. A Bayesian clustering approach via Markov chain Monte Carlo was performed to examine the genetic differentiation (F ST) among different genetic groups. The results indicated the existence of two distinct and strongly differentiated genetic groups. Cluster I contained 215 genotypes (56.3 %), over 60 % (137/215) of which were collected from CIMMYT. Cluster II showed the highest F ST value, according to 95 % credible interval. Linkage disequilibrium (LD) among SNPs was calculated for the A, B and D genomes and at the whole-genome level. LD decayed over a longer genetic distance for the D genome than for the A and B genomes. In the A and B genomes, LD declined to 50 % of its initial value at about 2 cM. In the D genome, LD was much more extensive, declining to 50 % of its initial value only at 22 cM. In the whole genome, LD declined to 50 % of its initial value at an average of 4 cM. Important genomic regions associated with complex traits in spring wheat were identified. Selection on these regions may increase the efficiency of the current breeding programs. Although most of the associations were environment specific, some stable associations were detected for Δ13C, KS, PH and TKW. Chromosomes 1A, 3A, 4A and 5A were the most important chromosomes, as they comprised quantitative trait loci (QTL) for Δ13C, a trait that can be used as an indirect tool for increased water-use efficiency in wheat. Environment-specific genomic regions were detected, indicating the presence of QTL-by-environment interaction. To produce suitable genotypes under contrasting water availability conditions, QTL × E interactions (and genotype-by-environment interaction) should be considered in the current spring wheat breeding program.

Combined effects of arbuscular mycorrhizal fungi and exogenous cytokinins on pomegranate (Punica granatum) under two contrasting water availability conditions

To our knowledge, there are no studies on the interactive effects of inoculation with arbuscular mycorrhizal fungi and cytokinin addition to plants under drought stress. We investigated the potential protective effect of arbuscular mycorrhizae on pomegranate plants, combined with exogenous cytokinin addition, under two contrasting soil water availability regimes. Our results showed that exogenous cytokinin addition enhances plant biomass, shoot to root ratio and water content, as well as increasing the anthocyanin content. However, a combination of AM fungal inoculation and cytokinin addition did not result in a synergistic protective effect against water stress. Plants were equally well protected against this stress by cytokinin spraying alone. The improvement of pomegranate growth was due mainly to exogenous cytokinin addition. Photosynthesis was promoted both by mycorrhizal inoculation alone and by exogenous cytokinin addition. The main protection against oxidative stress caused by drought was via enhanced accumulation of anthocyanins when the plants were sprayed with cytokinins. When cytokinins were used, the photosynthesis apparatus was also protected.

Effect of Arbuscular Mycorrhizal Fungi on Water Relations and Growth of Young Plum Trees under Severe Water Stress Conditions

Aims: Arbuscular mycorrhizal fungi (AMF) can mitigate plant response to severe water stress. On this basis, an experiment was carried out under field conditions to evaluate the effect of arbuscular mycorrhization, realized by a mixture of two AMF species, Rhizophagus intraradices and Funneliformis mosseae, on drought tolerance of young plum trees. Study Design: The experimental design was a criss cross with three variable factors: water regime, mycorrhization and plum variety. Place and Duration of Study: the trial was conducted during one year (2013) under field condition in experimental station Ain Taoujdate of the Regional Agricultural Research Center of Meknes, in northern Morocco. Methodology: The experiment was performed on four one year old mycorrhizal and nonmycorrhizal plum varieties submitted to two water regimes, 50% and 100% of crop evapotranspiration (ETc). Measurements have concerned vegetative growth parameters (shoot elongation, trunk growth and leaf area), water status (predawn and midday leaf water potential, Original Research Article Razouk and Kajji; IJPSS, 5(5): 300-312, 2015; Article no.IJPSS.2015.083 301 stomatal conductance and leaf relative water content) and leaf phosphorus content). Results: the young plum trees, even mycorrhized, did not tolerate water stress applied. However, plants were dependent on AMF under water stress, highly compensating its effects even at 50% of ETc. The compensatory effect of AMF was related to an increase of water potential and stomatal conductance without changing relative water content of plants. AMF also induced a significant increase of phosphorus uptake under water stress. Conclusion: it was demonstrated that AMF significantly improve water and nutrient use efficiency of young plum trees submitted to water stress amounting to 50% of ETc. The observed improvements due to AMF were considerable, suggesting possibility of adoption of this water restriction to optimize deficit irrigation of mycorrhizal plants of this rosacea under low water availability conditions.

Is Discrimination of 13C in Potato Leaflets and Tubers an Appropriate Trait to Describe Genotype Responses to Restrictive and Well‐Watered Conditions?

AbstractSelection for drought tolerance entails prioritizing plant traits that integrate critical physiological processes occurring during crop growth. Discrimination against 13C (∆) in leaflets (∆leaflet) and tubers (∆tuber) was compared under two water regimes in two potato‐improved varieties selected to maintain yield under drought conditions (Unica and Sarnav) and one drought susceptible European cultivar (Désirée). In the control treatment, soil water content was kept at field capacity over the whole growth cycle, while in the drought treatment water supply was restricted after tuber initiation (50 % of field capacity). Gas exchange and N content per unit leaf area (Narea) as well as ∆ were assessed at different stages. Sarnav showed the highest tuber yield in both water conditions, suggesting that yield in the water restriction treatment was largely driven by yield potential in this genotype. Higher stomatal conductance (gs) and Narea and lower ∆leaflet in well‐watered Sarnav suggested higher photosynthetic capacity. Under water restriction, Sarnav maintained higher gs indicating that carbon diffusion was a key factor for biomass accumulation under water restriction. Our results suggest the use of ∆ determined after tuber initiation as an indirect selection indicator for tuber yield under both well‐watered and restricted soil water availability conditions.

Effect of Drought Stress on Tomato cv. Bombino

To study “the effect of drought stress on Tomato (Lycopersicon esculentum) Cv. Bombino” an experiment was conducted at Institute of Biotechnology and Genetic Engineering, Agricultural University Peshawar. Tomato plants were grown in green house under two different conditions of water availability i.e.- controlled and drought. The parameters studied were relative water content (%), proline content (μmoles) and relative growth rate (week?1). Drought stress has significant effect on all parameters studied. The relative water content of plant body decline during drought due to less water availability. In controlled environment, the mean value of relative water content was 89.28 while that observed in drought condition was 87.73. Proline was observed on rise due to continuous decrease in water quantity in cell sap. The value of proline content is 4.4 μmoles g?1 fresh weight in controlled condition whereas that the plants in drought condition had 5.8 μmoles g?1 fresh weight. Due to less water, photosynthesis was negatively affected which resulted in less energy production and finally low growth. In controlled condition the relative growth rate week?1 on fresh weight was 1.37 gm whereas that of plant in drought condition was 0.57 gm.

Quantifying the economic importance of irrigation water reuse in a Chilean watershed using an integrated agent-based model

Irrigation with surface water enables Chilean agricultural producers to generate one of the country's most important economic exports. The Chilean water code established tradable water rights as a mechanism to allocate water amongst farmers and other water-use sectors. It remains contested whether this mechanism is effective and many authors have raised equity concerns regarding its impact on water users. For example, speculative hoarding of water rights in expectations of their increasing value has been described. This paper demonstrates how farmers can hoard water rights as a risk management strategy for variable water supply, for example, due to the cycles of El Nino or as consequence of climate change. While farmers with insufficient water rights can rely on unclaimed water during conditions of normal water availability, drought years overproportionally impact on their supply of irrigation water and thereby farm profitability. This study uses a simulation model that consists of a hydrological balance model component and a multiagent farm decision and production component. Both model components are parameterized with empirical data, while uncertain parameters are calibrated. The study demonstrates a thorough quantification of parameter uncertainty, using global sensitivity analysis and multiple behavioral parameter scenarios.

Flood Frequency Analysis of Tel Basin of Mahanadi River System, India Using Annual Maximum and POT Flood Data

Flood frequency analysis indicates the catchment characteristics, water availability and possible extreme hydrological conditions like floods and droughts at various locations of any river system. Such studies have been done in the past using long term annual maximum flood series for early warning, preparedness, mitigation and reduction of any kind of disasters. In the present study, Annual Maximum (AM) flood series and Peak over Threshold (POT) flood series were used to carry out flood frequency analysis for Tel basin of Mahanadi river system, India. The POT values were considered based on (a) commonly used standard practice and (b) flood values damaging the downstream areas and causing disaster in Mahanadi river system, India. To recognize the anomalies in tail behavior of the flood frequency distribution and for selecting appropriate flood frequency distributions, Quantile-Quantile plots (Q-Q plots) were used. The analysis was carried out for flood series data of two gauging stations Kesinga (upstream) and Kantamal (downstream) of Tel basin, Mahanadi river system, India for the years 1972-2009. Fourteen different flood frequency distributions were tried for AM and POT flood series data for 31 years for Kesinga and 38 years for Kantamal. The results obtained using Generalized Pareto (GP) distribution shows better results for AM flood data series with all goodness of fit tests. However, for POT flood data series LogNormal (3P) distribution showed best results followed by GP distributions with all goodness of fit test. The distributions most suitable for POT data sets are same for the distribution being used globally for flood forecasting.

Величина подколосового междоузлия и продуктивность сортов яровой мягкой пшеницы разных экологических групп в лесостепи Оренбургского Предуралья

The impact of contrasting conditions of water availability on the size of the upper internodes in wheat varieties was studied under the conditions of the Orenburg steppe zone. It was noted, that less drought-resistant varieties formed a short upper internodes. We conducted a mathematical analysis of the relationship of productivity and length of ear-carrying internodes of spring soft wheat varieties of different ecological groups. It was established, that we can observe a gradual increase of grain productivity with increasing the length of the upper internodes in the studied range. As a result, the following varities were selected for inclusion into the hybridization: Logachevka, Tulaykovskaya steppe, Tulaykovskaya 1, Tulaykovskaya Belozernaya, Prokhorovka and Uchitel. They have the optimal settings for the presented feature. Using the selected varieties as parental forms can enhance the efficiency of wheat breeding programs for resistance to drought in the forest-steppe zone of the Southern Urals.

Transpiration and biomass production of the bioenergy crop Giant Knotweed Igniscum under various supplies of water and nutrients

Abstract Soil water availability, nutrient supply and climatic conditions are key factors for plant production. For a sustainable integration of bioenergy plants into agricultural systems, detailed studies on their water uses and growth performances are needed. The new bioenergy plant Igniscum Candy is a cultivar of the Sakhalin Knotweed (Fallopia sachalinensis), which is characterized by a high annual biomass production. For the determination of transpiration-yield relations at the whole plant level we used wicked lysimeters at multiple irrigation levels associated with the soil water availability (25, 35, 70, 100%) and nitrogen fertilization (0, 50, 100, 150 kg N ha-1). Leaf transpiration and net photosynthesis were determined with a portable minicuvette system. The maximum mean transpiration rate was 10.6 mmol m-2 s-1 for well-watered plants, while the mean net photosynthesis was 9.1 μmol m-2 s-1. The cumulative transpiration of the plants during the growing seasons varied between 49 l (drought stressed) and 141 l (well-watered) per plant. The calculated transpiration coefficient for Fallopia over all of the treatments applied was 485.6 l kg-1. The transpiration-yield relation of Igniscum is comparable to rye and barley. Its growth performance making Fallopia a potentially good second generation bioenergy crop.

Response of grapevine cv. Syrah to irrigation frequency and water distribution pattern in a clay soil

Water availability is one of the major factors that determine vineyard performance in many grape growing regions, so its implications have been widely studied before. However, for a given irrigation water amount, other aspects such as application frequency, or emitter spacing and flow rate (i.e., distribution pattern), may play a relevant role, but these factors have been scarcely studied. The aim of this work was to evaluate the agronomic implications of two irrigation frequencies (IrrF, every 2 and 4 days) and two water distribution patterns (DisP, 2Lh−1 emitters every 0.6m vs. 4Lh−1 emitters every 1.2m). The experiment was carried out during four consecutive seasons in a cv. Syrah vineyard with a clay soil in central Spain, and the two factors were evaluated under two water availability conditions (low and medium). IrrF and DisP promoted changes in water status that affected some aspects of vegetative development and yield components under both water availability conditions, although the effects observed were not the same every year. Berry size was the most sensitive parameter to changes in IrrF and DisP. The effects were more evident under low water availability. Soil texture has certainly conditioned the results obtained, since high frequency irrigation implied applying small amounts of water that resulted in limited superficial water bulbs, which probably favored water evaporation.

Carbon balance, partitioning and photosynthetic acclimation in fruit-bearing grapevine (Vitis vinifera L. cv. Tempranillo) grown under simulated climate change (elevated CO2, elevated temperature and moderate drought) scenarios in temperature gradient greenhouses

Although plant performance under elevated CO2 has been extensively studied in the past little is known about photosynthetic performance changing simultaneously CO2, water availability and temperature conditions. Moreover, despite of its relevancy in crop responsiveness to elevated CO2 conditions, plant level C balance is a topic that, comparatively, has received little attention. In order to test responsiveness of grapevine photosynthetic apparatus to predicted climate change conditions, grapevine (Vitis vinifera L. cv. Tempranillo) fruit-bearing cuttings were exposed to different CO2 (elevated, 700ppm vs. ambient, ca. 400ppm), temperature (ambient vs. elevated, ambient +4°C) and irrigation levels (partial vs. full irrigation). Carbon balance was followed monitoring net photosynthesis (AN, C gain), respiration (RD) and photorespiration (RL) (C losses). Modification of environment 13C isotopic composition (δ13C) under elevated CO2 (from −10.30 to −24.93‰) enabled the further characterization of C partitioning into roots, cuttings, shoots, petioles, leaves, rachides and berries. Irrespective of irrigation level and temperature, exposure to elevated CO2 induced photosynthetic acclimation of plants. C/N imbalance reflected the inability of plants grown at 700ppm CO2 to develop strong C sinks. Partitioning of labeled C to storage organs (main stem and roots) did not avoid accumulation of labeled photoassimilates in leaves, affecting negatively Rubisco carboxylation activity. The study also revealed that, after 20 days of treatment, no oxidative damage to chlorophylls or carotenoids was observed, suggesting a protective role of CO2 either at current or elevated temperatures against the adverse effect of water stress.

A Group 6 Late Embryogenesis Abundant Protein from Common Bean Is a Disordered Protein with Extended Helical Structure and Oligomer-forming Properties

Late embryogenesis-abundant proteins accumulate to high levels in dry seeds. Some of them also accumulate in response to water deficit in vegetative tissues, which leads to a remarkable association between their presence and low water availability conditions. A major sub-group of these proteins, also known as typical LEA proteins, shows high hydrophilicity and a high percentage of glycine and other small amino acid residues, distinctive physicochemical properties that predict a high content of structural disorder. Although all typical LEA proteins share these characteristics, seven groups can be distinguished by sequence similarity, indicating structural and functional diversity among them. Some of these groups have been extensively studied; however, others require a more detailed analysis to advance in their functional understanding. In this work, we report the structural characterization of a group 6 LEA protein from a common bean (Phaseolus vulgaris L.) (PvLEA6) by circular dichroism and nuclear magnetic resonance showing that it is a disordered protein in aqueous solution. Using the same techniques, we show that despite its unstructured nature, the addition of trifluoroethanol exhibited an intrinsic potential in this protein to gain helicity. This property was also promoted by high osmotic potentials or molecular crowding. Furthermore, we demonstrate that PvLEA6 protein is able to form soluble homo-oligomeric complexes that also show high levels of structural disorder. The association between PvLEA6 monomers to form dimers was shown to occur in plant cells by bimolecular fluorescence complementation, pointing to the in vivo functional relevance of this association.

Maize Root Architecture and Water Stress Tolerance: An Approximation from Crop Models

This work presents an assessment of potential advantages of drought tolerance in maize (Zea mays L.) production. A higher water uptake resulting from an enhanced root exploration at deep soil layers seems to be the most promising mechanism. The potential field‐level impacts of this mechanism is assessed in two contrasting agroecological areas of the Argentine Pampas using the CERES‐Maize model. The soil root growth factor parameter (SRGF) was manipulated to represent a modified maize hybrid with higher density of deep roots. Enhanced root exploration increased maize transpiration and consequently biomass production and yields. Benefits of the modified hybrid tend to be higher under low water availability conditions (low soil water content at sowing and/or rains during crop cycle). Although higher yield responses to root architecture changes were initially expected in the marginal semiarid area (Pilar), the opposite was observed: the average yield increases were 4.7 and 11.7% for Pilar and Pergamino, respectively. The modified hybrid showed lower yields than the current one in approximately 10% of the simulated situations. There were no yield penalties for the modified hybrid in cropping cycles with high water availability. This work shows strong interactions between root architecture and the environmental conditions in which crops are grown that affect potential field‐level benefits. We highlight the need for assessing attributes tied to drought tolerance in the context of agroecological conditions in which plants will be grown to identify which drought‐tolerance mechanisms might prove effective under different water‐stress conditions.

An adaptive ant colony optimization framework for scheduling environmental flow management alternatives under varied environmental water availability conditions

AbstractHuman water use is increasing and, as such, water for the environment is limited and needs to be managed efficiently. One method for achieving this is the scheduling of environmental flow management alternatives (EFMAs) (e.g., releases, wetland regulators), with these schedules generally developed over a number of years. However, the availability of environmental water changes annually as a result of natural variability (e.g., drought, wet years). To incorporate this variation and schedule EFMAs in a operational setting, a previously formulated multiobjective optimization approach for EFMA schedule development used for long‐term planning has been modified and incorporated into an adaptive framework. As part of this approach, optimal schedules are updated at regular intervals during the planning horizon based on environmental water allocation forecasts, which are obtained using artificial neural networks. In addition, the changes between current and updated schedules can be minimized to reduce any disruptions to long‐term planning. The utility of the approach is assessed by applying it to an 89km section of the River Murray in South Australia. Results indicate that the approach is beneficial under a range of hydrological conditions and an improved ecological response is obtained in a operational setting compared with previous long‐term approaches. Also, it successfully produces trade‐offs between the number of disruptions to schedules and the ecological response, with results suggesting that ecological response increases with minimal alterations required to existing schedules. Overall, the results indicate that the information obtained using the proposed approach potentially aides managers in the efficient management of environmental water.