Pre-Harvest Salicylic Acid Application Affects Fruit Quality and Yield under Deficit Irrigation in Aristotelia chilensis (Mol.) Plants.

Salicylic acid (SA) application is a promising agronomic tool. However, studies under field conditions are required, to confirm the potential benefits of SA. Thus, SA application was evaluated under field conditions for its effect on abscisic acid levels, antioxidant related-parameters, fruit quality, and yield in Aristotelia chilensis subjected to different levels of irrigation. During two growing seasons, three-year-old plants under field conditions were subjected to full irrigation (FI: 100% of reference evapotranspiration (ETo), and deficit irrigation (DI: 60% ETo). During each growth season, a single application of 0.5 mM SA was performed at fruit color change by spraying fruits and leaves of both irrigation treatments. The results showed that DI plants experienced moderate water stress (-1.3 MPa), which increased ABA levels and oxidative stress in the leaves. The SA application facilitated the recovery of all physiological parameters under the DI condition, increasing fruit fresh weight by 44%, with a 27% increase in fruit dry weight, a 1 mm increase in equatorial diameter, a 27% improvement in yield per plant and a 27% increase in total yield, with lesser oxidative stress and tissue ABA levels in leaves. Also, SA application significantly increased (by about 10%) the values of fruit trait variables such as soluble solids, total phenols, and antioxidant activity, with the exceptions of titratable acidity and total anthocyanins, which did not vary. The results demonstrated that SA application might be used as an agronomic strategy to improve fruit yield and quality, representing a saving of 40% regarding water use.

Seed Priming with Glass Waste Microparticles and Red Light Irradiation Mitigates Thermal and Water Stresses in Seedlings of Moringa oleifera.

The association between population increase and the exploitation of natural resources and climate change influences the demand for food, especially in semi-arid regions, highlighting the need for technologies that could provide cultivated species with better adaptation to agroecosystems. Additionally, developing cultivation technologies that employ waste materials is highly desirable for sustainable development. From this perspective, this study aimed to evaluate whether seed priming with glass waste microparticles used as a silicon source under red light irradiation mitigates the effects of thermal and water stress on seedlings of Moringa oleifera. The experimental design was set up in randomized blocks using a 2 × 2 × 2 factorial arrangement consisting of seed priming (NSP-no seed priming, and SPSi-seed priming with glass microparticles under red light irradiation), soil water replenishment (W50-50%, and W100-100% of crop evapotranspiration-ETc), and temperature change (TC30°-30 °C day/25 °C night and TC40°-40 °C day/35 °C night). Seed priming with glass microparticles under red light irradiation mitigated the effects of thermal and water stress on seedlings of Moringa oleifera seedlings through the homeostasis of gas exchange, leaf water status, osmotic adjustment, and the antioxidant mechanism.

Upland rice: phenotypic diversity for drought tolerance

Upland rice is cultivated mostly in Latin America and Africa by small farmers and in areas with risk of dry spells. This study evaluated morphophysiological mechanisms of upland rice associated to drought adaptation. A set of 25 upland rice genotypes were grown in a plant phenotyping platform during 2015 and 2017 under regular irrigation and water restriction. We evaluated morphophysiological traits in shoots (vegetative structures growth, gas exchange, water use efficiency, carboxylation efficiency, water status) and roots (length, surface area, volume and diameter), as well as agronomic traits (grain yield and its components). There was a reduction in grain yield by up to 54 % and 58 % in 2015 and 2017, respectively, under water deficit. Five upland rice genotypes with the best yield performances in both water treatments applied were recommended to the upland rice-breeding program: Bico Ganga, BRS Esmeralda, BRSMG Curinga, Guarani, and Rabo de Burro. In this study, morphophysiological traits associated to drought tolerance concerned the plant high capacity to save water in the leaves, low leaf water potential, high ability to reduce vegetative structures, high water use efficiency, high photosynthetic capacity, and improved capacity to absorb water from drying soil, either by osmotic adjustment or additional investment into the root system. Therefore, we concluded that different secondary traits contributed to drought tolerance and should be evaluated along with grain yield to improve efficiency of breeding selection.(AU)

Upland rice: phenotypic diversity for drought tolerance

Upland rice is cultivated mostly in Latin America and Africa by small farmers and in areas with risk of dry spells. This study evaluated morphophysiological mechanisms of upland rice associated to drought adaptation. A set of 25 upland rice genotypes were grown in a plant phenotyping platform during 2015 and 2017 under regular irrigation and water restriction. We evaluated morphophysiological traits in shoots (vegetative structures growth, gas exchange, water use efficiency, carboxylation efficiency, water status) and roots (length, surface area, volume and diameter), as well as agronomic traits (grain yield and its components). There was a reduction in grain yield by up to 54 % and 58 % in 2015 and 2017, respectively, under water deficit. Five upland rice genotypes with the best yield performances in both water treatments applied were recommended to the upland rice-breeding program: Bico Ganga, BRS Esmeralda, BRSMG Curinga, Guarani, and Rabo de Burro. In this study, morphophysiological traits associated to drought tolerance concerned the plant high capacity to save water in the leaves, low leaf water potential, high ability to reduce vegetative structures, high water use efficiency, high photosynthetic capacity, and improved capacity to absorb water from drying soil, either by osmotic adjustment or additional investment into the root system. Therefore, we concluded that different secondary traits contributed to drought tolerance and should be evaluated along with grain yield to improve efficiency of breeding selection.

Root Architecture and Functional Traits of Spring Wheat Under Contrasting Water Regimes.

Wheat roots are known to play an important role in the yield performance under water-limited (WL) conditions. Three consecutive year trials (2015, 2016, and 2017) were conducted in a glasshouse in 160 cm length tubes on a set of spring wheat (Triticum aestivum L.) genotypes under contrasting water regimes (1) to assess genotypic variability in root weight density (RWD) distribution in the soil profile, biomass partitioning, and total water used; and (2) to determine the oxygen and hydrogen isotopic signatures of plant and soil water in order to evaluate the contribution of shallow and deep soil water to plant water uptake and the evaporative enrichment of these isotopes in the leaf as a surrogate for plant transpiration. In the 2015 trial under well-watered (WW) conditions, the aerial biomass (AB) was not significantly different among 15 wheat genotypes, while the total root biomass and the RWD distribution in the soil profile were significantly different. In the 2016 and 2017 trials, a subset of five genotypes from the 2015 trial was grown under WW and WL regimes. The water deficit significantly reduced AB only in 2016. The water regimes did not significantly affect the root biomass and root biomass distribution in the soil depths for both the 2016 and 2017 trials. The study results highlighted that under a WL regime, the production of thinner roots with low biomass is more beneficial for increasing the water uptake than the production of large thick roots. The models applied to estimate the relative contribution of the plant's primary water sources (shallow or deep soil water) showed large interindividual variability in soil, and plant water isotopic composition resulted in large uncertainties in the model estimates. On the other side, the combined information of root architecture and the leaf stable isotope signatures could explain plant water status.

Physiological characterization of common bean (Phaseolus vulgaris L.) under abiotic stresses for breeding purposes.

In the Brazilian wet and dry seasons, common beans (Phaseolus vulgaris L.) are grown under rainfed conditions with unexpected episodes of drought and high temperatures. The objective of this study was to evaluate the physiological mechanisms associated with drought adaptation traits in landraces and line/cultivars of beans from the Andean and Mesoamerican gene pools. Twenty-five genotypes, contrasting in terms of drought tolerance, were evaluated in a phenotyping platform under irrigated and rainfed conditions. Agronomic and physiological parameters such as grain yield, shoot structures, gas exchange, water potential, and osmotic adjustment were evaluated. The stress intensity was estimated to be 0.57, and the grain yield reduction ranged from 22 to 89%. Seven accessions, representative of the Andean and Mesoamerican germplasm (CF 200012, CF 240056, CF 250002, CF 900004, CNF 4497, CNF 7382, and SEA 5), presented superior performance in grain yield with and without stresses. The physiological responses under abiotic stresses were highly variable among the genotypes, and two Mesoamerican accessions (CF 200012 and SEA 5) showed more favorable adaptive responses. As the main secondary physiological traits, gas exchange and osmotic adjustment should be evaluated together with the grain yield to increase the selection efficiency of abiotic stresses-tolerant common bean lines.

Effects of Three Irrigation Strategies on Gas Exchange Relationships, Plant Water Status, Yield Components and Water Productivity on Grafted Carménère Grapevines.

In the Chilean viticultural industry, Carménère is considered an emblematic cultivar that is cultivated mainly in arid and semi-arid zones. For this reason, it is necessary to use precise irrigation scheduling for improving water use efficiency (WUE), water productivity (WP), yield and wine quality. This study evaluated the effects of three deficit irrigation strategies on gas exchange variables, WUE, WP and yield components in a drip-irrigated Carménère vineyard growing under semi-arid climatic conditions during two consecutive seasons (2011/12 and 2012/13). The irrigation strategies were applied in completely randomized design from fruit set (S) to harvest (H). The first irrigation strategy (T1) involved continuous irrigation at 100% of actual evapotranspiration (ETa) from S to the veraison (V) period and at 80% of ETa from V to H. The second irrigation strategy (T2) involved irrigation at 50% of ETa from S to H and the third one (T3) involved no-irrigation from S to V and at 30% of ETa from V to H. The results indicated that there was a significant non-linear correlation between net CO2 assimilation (AN) and stomatal conductance (gs), which resulted in three zones of water stress (zone I = gs > 0.30 mol H2O m-2s-1; zone II = between 0.06 and 0.30 mol H2O m-2s-1; and zone III = gs < 0.06 mol H2O m-2s-1). The use of less water by T2 and T3 had a significant effect on yield components, with a reduction in the weight and diameter of grapes. A significant increase in WP (7.3 kg m-3) occurred in T3, which resulted in values of WUE that were significantly higher than those from T1 and T2. Also, a significant non-linear relationship between the integral water stress (SIΨ) and WP (R2 = 0.74) was established. The results show that grafted Carménère vines were tolerant to water stress although differences between cultivars/genotypes still need to be evaluated.

Two approaches to calculate TVDI in humid subtropical climate of southern Brazil

Soybean crops occupy most areas in Rio Grande do Sul State and are highly dependent on rainfall since most of them are non-irrigated. Rainfall during the harvest period is often insufficient to meet the water demand, making water indicators an important tool for the crops. This study compared two approaches in the parameterization process of TVDI (Temperature-Vegetation Dryness Index) in a subtropical climate region of Brazil. The process used Moderate Resolution Imaging Spectroradiometer (MODIS) images of the surface temperature (TS) and Normalized Difference Vegetation Index (NDVI), with spatial resolutions of 1,000 m and periods of 8-16 d, respectively. The evaporative triangles for the TS/NDVI scatter plots were built either for each image (scene-specific parameterization) or for all images at once (crop-type parameterization). The rainfall data were obtained from meteorological stations located in the study site and the analysis period comprised two contrasting harvests regarding soybean yield (most important crop in the region). The scene-specific parameterization allowed to analyze water status in the study site by inspecting the wet and dry edge of each image and identifying the areas of stress in each one. TVDI crop parameterization showed that the model was able to determine the time and frequency of water stress events during the crop-seasons. TVDI crop-parameterization, therefore, is more consistent for crop monitoring and forecasting purposes.(AU)

Two approaches to calculate TVDI in humid subtropical climate of southern Brazil

Soybean crops occupy most areas in Rio Grande do Sul State and are highly dependent on rainfall since most of them are non-irrigated. Rainfall during the harvest period is often insufficient to meet the water demand, making water indicators an important tool for the crops. This study compared two approaches in the parameterization process of TVDI (Temperature-Vegetation Dryness Index) in a subtropical climate region of Brazil. The process used Moderate Resolution Imaging Spectroradiometer (MODIS) images of the surface temperature (TS) and Normalized Difference Vegetation Index (NDVI), with spatial resolutions of 1,000 m and periods of 8-16 d, respectively. The evaporative triangles for the TS/NDVI scatter plots were built either for each image (scene-specific parameterization) or for all images at once (crop-type parameterization). The rainfall data were obtained from meteorological stations located in the study site and the analysis period comprised two contrasting harvests regarding soybean yield (most important crop in the region). The scene-specific parameterization allowed to analyze water status in the study site by inspecting the wet and dry edge of each image and identifying the areas of stress in each one. TVDI crop parameterization showed that the model was able to determine the time and frequency of water stress events during the crop-seasons. TVDI crop-parameterization, therefore, is more consistent for crop monitoring and forecasting purposes.

Physiological response of Cucurbita pepo var. pepo mycorrhized by Sonoran desert native arbuscular fungi to drought and salinity stresses

Plants response to symbiosis with arbuscular mycorrhizal fungi (AMF) under water stress is important to agriculture. Under abiotic stress conditions native fungi are more effective than exotics in improving plant growth and water status. Mycorrhization efficiency is related to soil fungi development and energy cost-benefit ratio. In this study, we assessed the effect on growth, water status and energy metabolism of Cucurbita pepo var. pepo when inoculated with native AMF from the Sonoran desert Mexico (mixed isolate and field consortium), and compared with an exotic species from a temperate region, under drought, low and high salinity conditions. Dry weights, leaf water content, water and osmotic potentials, construction costs, photochemistry and mycorrhization features were quantified. Under drought and low salinity conditions, the mixed isolate increased plant growth and leaf water content. Leaf water potential was increased only by the field consortium under drought conditions (0.5-0.9 MPa). Under high salinity, the field consortium increased aerial dry weight (more than 1 g) and osmotic potential (0.54 MPa), as compared to non-mycorrhized controls. Plants inoculated with native AMF, which supposedly diminish the effects of stress, exhibited low construction costs, increased photochemical capacity, and grew larger external mycelia in comparison to the exotic inoculum.(AU)

Physiological response of Cucurbita pepo var. pepo mycorrhized by Sonoran desert native arbuscular fungi to drought and salinity stresses

ABSTRACT Plants response to symbiosis with arbuscular mycorrhizal fungi (AMF) under water stress is important to agriculture. Under abiotic stress conditions native fungi are more effective than exotics in improving plant growth and water status. Mycorrhization efficiency is related to soil fungi development and energy cost-benefit ratio. In this study, we assessed the effect on growth, water status and energy metabolism of Cucurbita pepo var. pepo when inoculated with native AMF from the Sonoran desert Mexico (mixed isolate and field consortium), and compared with an exotic species from a temperate region, under drought, low and high salinity conditions. Dry weights, leaf water content, water and osmotic potentials, construction costs, photochemistry and mycorrhization features were quantified. Under drought and low salinity conditions, the mixed isolate increased plant growth and leaf water content. Leaf water potential was increased only by the field consortium under drought conditions (0.5-0.9 MPa). Under high salinity, the field consortium increased aerial dry weight (more than 1 g) and osmotic potential (0.54 MPa), as compared to non-mycorrhized controls. Plants inoculated with native AMF, which supposedly diminish the effects of stress, exhibited low construction costs, increased photochemical capacity, and grew larger external mycelia in comparison to the exotic inoculum.

Physiological response of Cucurbita pepo var. pepo mycorrhized by Sonoran desert native arbuscular fungi to drought and salinity stresses.

Plants response to symbiosis with arbuscular mycorrhizal fungi (AMF) under water stress is important to agriculture. Under abiotic stress conditions native fungi are more effective than exotics in improving plant growth and water status. Mycorrhization efficiency is related to soil fungi development and energy cost-benefit ratio. In this study, we assessed the effect on growth, water status and energy metabolism of Cucurbita pepo var. pepo when inoculated with native AMF from the Sonoran desert Mexico (mixed isolate and field consortium), and compared with an exotic species from a temperate region, under drought, low and high salinity conditions. Dry weights, leaf water content, water and osmotic potentials, construction costs, photochemistry and mycorrhization features were quantified. Under drought and low salinity conditions, the mixed isolate increased plant growth and leaf water content. Leaf water potential was increased only by the field consortium under drought conditions (0.5-0.9MPa). Under high salinity, the field consortium increased aerial dry weight (more than 1g) and osmotic potential (0.54MPa), as compared to non-mycorrhized controls. Plants inoculated with native AMF, which supposedly diminish the effects of stress, exhibited low construction costs, increased photochemical capacity, and grew larger external mycelia in comparison to the exotic inoculum.

Yield and Water Productivity Responses to Irrigation Cut-off Strategies after Fruit Set Using Stem Water Potential Thresholds in a Super-High Density Olive Orchard.

An increase in the land area dedicated to super-high density olive orchards has occurred in Chile in recent years. Such modern orchards have high irrigation requirements, and optimizing water use is a priority. Moreover, this region presents low water availability, which makes necessary to establish irrigation strategies to improve water productivity. An experiment was conducted during four consecutive growing seasons (2010-2011 to 2013-2014) to evaluate the responses of yield and water productivity to irrigation cut-off strategies. These strategies were applied after fruit set using midday stem water potential (Ψstem) thresholds in a super-high density olive orchard (cv. Arbequina), located in the Pencahue Valley, Maule Region, Chile. The experimental design was completely randomized with four irrigation cut-off treatments based on the Ψstem thresholds and four replicate plots per treatment (five trees per plot). Similar to commercial growing conditions in our region, the Ψstem in the T1 treatment was maintained between -1.4 and -2.2 MPa (100% of actual evapotranspiration), while T2, T3 and T4 treatments did not receive irrigation from fruit set until they reached a Ψstem threshold of approximately -3.5, -5.0, and -6.0 MPa, respectively. Once the specific thresholds were reached, irrigation was restored and maintained as T1 in all treatments until fruits were harvested. Yield and its components were not significantly different between T1 and T2, but fruit yield and total oil yield, fruit weight, and fruit diameter were decreased by the T3 and T4 treatments. Moreover, yield showed a linear response with water stress integral (SΨ), which was strongly influenced by fruit load. Total oil content (%) and pulp/stone ratio were not affected by the different irrigation strategies. Also, fruit and oil water productivities were significantly greater in T1 and T2 than in the T3 and T4. Moreover, the T2, T3, and T4 treatments averaged 37, 51, and 72 days without irrigation which represented 75-83, 62-76, and 56-70% of applied water compared with T1, respectively. These results suggest that using the T2 irrigation cut-off strategy could be applied in a super-high density olive orchard (cv. Arbequina) because it maintained yields, saving 20% of the applied water.

Enzymatic antioxidant responses to biostimulants in maize and soybean subjected to drought

Water stress is one of the most important environmental factors inducing physiological changes in plants, such as decrease in the water potential of the cells, the stomatal closure; and the development of oxidative processes mediated by reactive oxygen species (ROS). Antioxidant enzymes superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX) are efficient scavengers of ROS. The aim of this research was to examine how the application of biostimulant based on humic substances and aminoacids may affect activity levels of SOD, CAT, and APX of maize and soybean plants under well-watered or drought stress conditions. Pots (4.5 L) were filled with a Typic Hapludult soil where the biostimulants doses were applied. It was taken leaf samples in order to analyze SOD, CAT, and APX activities in plants. SOD and APX activity levels were increased by application of biostimulant 1 in maize subjected to stress. Catalase activity was not enhanced in plants by using the biostimulants. The composition of the biostimulants was not able to enhance stress tolerance in maize and soybean plants subjected to water stress.

O estresse hídrico é um dos mais importantes fatores ambientais que induz mudanças fisiológicas, como diminuição do potencial de água na célula, o fechamento dos estômatos e o desenvolvimento de processos oxidativos mediante a formação das espécies reativas de oxigênio (ROS). As enzimas antioxidantes superóxido dismutase (SOD), catalase (CAT) e ascorbato peroxidase (APX) são eficientes eliminadores das ROS. O objetivo deste estudo foi examinar como a aplicação de bioestimulantes com substâncias húmicas e aminoácidos em sua composição afeta os níveis de SOD, CAT e APX nos tecidos das folhas de plantas de milho e de soja cultivadas com ou sem estresse hídrico. Amostras de um Argissolo foram colocadas em vasos (4,5 L) onde foram adicionadas as doses dos bioestimulantes. Foram retiradas amostras de folhas para análise da atividade da SOD, CAT e APX nas plantas. A SOD e APX aumentaram nas plantas de milho com a aplicação do bioestimulante 1. A atividade da CAT não aumentou nas plantas com a aplicação dos bioestimulantes. As composições dos bioestimulantes não possibilitaram aumento na resistência ao estresse hídrico em plantas de milho e de soja submetidas ao estresse hídrico

Enzymatic antioxidant responses to biostimulants in maize and soybean subjected to drought

Water stress is one of the most important environmental factors inducing physiological changes in plants, such as decrease in the water potential of the cells, the stomatal closure; and the development of oxidative processes mediated by reactive oxygen species (ROS). Antioxidant enzymes superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX) are efficient scavengers of ROS. The aim of this research was to examine how the application of biostimulant based on humic substances and aminoacids may affect activity levels of SOD, CAT, and APX of maize and soybean plants under well-watered or drought stress conditions. Pots (4.5 L) were filled with a Typic Hapludult soil where the biostimulants doses were applied. It was taken leaf samples in order to analyze SOD, CAT, and APX activities in plants. SOD and APX activity levels were increased by application of biostimulant 1 in maize subjected to stress. Catalase activity was not enhanced in plants by using the biostimulants. The composition of the biostimulants was not able to enhance stress tolerance in maize and soybean plants subjected to water stress.

O estresse hídrico é um dos mais importantes fatores ambientais que induz mudanças fisiológicas, como diminuição do potencial de água na célula, o fechamento dos estômatos e o desenvolvimento de processos oxidativos mediante a formação das espécies reativas de oxigênio (ROS). As enzimas antioxidantes superóxido dismutase (SOD), catalase (CAT) e ascorbato peroxidase (APX) são eficientes eliminadores das ROS. O objetivo deste estudo foi examinar como a aplicação de bioestimulantes com substâncias húmicas e aminoácidos em sua composição afeta os níveis de SOD, CAT e APX nos tecidos das folhas de plantas de milho e de soja cultivadas com ou sem estresse hídrico. Amostras de um Argissolo foram colocadas em vasos (4,5 L) onde foram adicionadas as doses dos bioestimulantes. Foram retiradas amostras de folhas para análise da atividade da SOD, CAT e APX nas plantas. A SOD e APX aumentaram nas plantas de milho com a aplicação do bioestimulante 1. A atividade da CAT não aumentou nas plantas com a aplicação dos bioestimulantes. As composições dos bioestimulantes não possibilitaram aumento na resistência ao estresse hídrico em plantas de milho e de soja submetidas ao estresse hídrico

Water relations in seed biology

The water relations play a fundamental role in seed biology. Thus, the purpose of the present paper was to analyze the performance of water status in seed development and germination. The researches have suggested that the water potential of the seed or seed structures provides a better indicator of the seed water status than water content. The seed water status plays a regulatory role in seed development and germination.

As relações hídricas exercem um importante papel na biologia da semente. Desta forma, o presente trabalho objetivou apresentar uma análise do comportamento do estado da água no desenvolvimento e na germinação da semente. As pesquisas mostram que o potencial hídrico da semente ou de suas estruturas pode constituir-se num indicador mais eficiente do estado da água do que o teor de água e que este estado apresenta um papel regulador no desenvolvimento e na germinação de sementes.

Water relations in seed biology

The water relations play a fundamental role in seed biology. Thus, the purpose of the present paper was to analyze the performance of water status in seed development and germination. The researches have suggested that the water potential of the seed or seed structures provides a better indicator of the seed water status than water content. The seed water status plays a regulatory role in seed development and germination.

As relações hídricas exercem um importante papel na biologia da semente. Desta forma, o presente trabalho objetivou apresentar uma análise do comportamento do estado da água no desenvolvimento e na germinação da semente. As pesquisas mostram que o potencial hídrico da semente ou de suas estruturas pode constituir-se num indicador mais eficiente do estado da água do que o teor de água e que este estado apresenta um papel regulador no desenvolvimento e na germinação de sementes.