Days Of Water Stress Research Articles

Responses of the sugarcane rhizosphere microbiota to different levels of water stress

The production of sugarcane, a globally important crop, is likely to be impacted by changes in climate including higher average temperatures and decreased rainfall in regions such as the northeast and southeast of Brazil. This metatranscriptome study investigated the effect of water stress on the microbiota associated with the sugarcane rhizosphere, in order to obtain new information about plant-microbiota interactions and the ways that microorganisms could help plants to survive under adverse conditions. The results indicated that water stress increased the exudation of organic acids from the plant roots and changed the microbial gene expression in the rhizosphere. Decreased expression of genes related to growth and energy metabolism was mainly evident in samples submitted to eight days of water stress and was classified to the genera Sorangium and Rhodanobacter. Genes associated with functions such as flagella mobility, cell adhesion, and protein degradation showed increased expression in the same time period, with these transcripts classified to the genus Aequorivita. This genus also showed a positive correlation with the organic acids exuded by the plant. These results contribute to an understanding of the dynamics of the rhizosphere microbial community under normal and water stress conditions, indicating possible microbial groups that may play important roles in the maintenance of sugarcane under water stress.

Teor e identificação química do óleo essencial de manjericão (ocimum basilicum, Var. cinamon)l submetido ao estresse hídrico em ambientes distintos

O manjericão (Ocimum basilicum L, Var.Cinamon) é uma das culturas com maior potencial para o mercado de exportação devido ser é uma espécie medicinal muito utilizada devido às características de seus óleos essenciais. O presente trabalho teve como objetivo avaliar geral avaliar o teor e identificação química do óleo essencial de manjericão (Ocimum basilicum L, var. Cinamon) submetido ao estresse hídrico em ambientes distintos. O delineamento experimental utilizado foi em blocos (DBC) com esquema fatorial 2 x 5, sendo dois tipos de ambientes no qual as plantas foram submetidas ao ambiente telado e a céu aberto e cinco dias de manejo de estresse. Para a identificação dos grupos funcionais foi utilizado à espectroscopia Raman de ATR. Os resultados evidenciaram a presença de alcoóis e fenóis apresentando bandas de estriamentos intensas de O-H (quelato) centradas entre 3000 e 2500 cm-1, constando- se assim, a presença desses dois grupos funcionais, majoritariamente. Os teores de óleo essencial das plantas submetidas à ambiente telado e a céu aberto não apresentaram diferença estatística. Constatou-se que os óleos essenciais coletados após cartoze dias de estresse hídrico e submetido à variável de ambiente telado apresentaram melhores resultados de picos e intensidade de absorção. Constatando- se, assim, a presença de alcoóis e fenóis como os grupos funcionais majoritários.

Modeling Climate Warming Impacts on Grain and Forage Sorghum Yields in Argentina

Sorghum is the world’s fifth major cereal in terms of production and acreage. It is expected that its growth will be affected by the increase in air temperature, an important component of global climate change. Our objective was to use the Agricultural Land Management Alternatives with Numerical Assessment Criteria (ALMANAC) model to (a) evaluate the impact of climate warming on forage and grain sorghum production in Argentina and (b) to analyze to what extent yield changes were associated with changes in water or nitrogen stress days. For model calibration, we used previous information related to the morpho-physiological characteristics of both sorghum types and several soil parameters. We then used multiyear field data of sorghum yields for model validation. Yield simulations were conducted under three possible climate change scenarios: 1, 2, and 4 °C increase in mean annual temperature. ALMANAC successfully simulated mean yields of forage and grain sorghum: root mean square error (RMSE): 2.6 and 1.0 Mg ha−1, respectively. Forage yield increased 0.53 Mg ha−1, and grain yield decreased 0.27 Mg ha−1 for each degree of increase in mean annual temperature. Yields of forage sorghum tended to be negatively associated with nitrogen stress (r = −0.94), while grain sorghum yield was negatively associated with water stress (r = −0.99). The information generated allows anticipating future changes in crop management and genetic improvement programs in order to reduce the yield vulnerability.

Growth response of Moringa oleifera (Lam) to water stress and to arid bioclimatic conditions

A major challenge in agroforestry is the selection of the plant species involved in the systems. This issue is drawing more attention lately due to the changing climate conditions and Moringa oleifera represents a promising species to meet these climatic challenges. The adaptation potential and tolerance of Moringa to water stress was tested in this study. It included a controlled (hydroponic cultivation) and a field experiment in an arid area bordering the Bouhedma National Park (Governorate of Sidi Bouzid) in Tunisia. Water stress was induced by the use of polyethylene glycol (PEG-6000) to create different water potential levels (ψh) and included 0 (control), −0.5, −1 and −1.5 MPa. The growth of the stem and main root, relative growth rate (RGRh), and leaf area (LA) of Moringa seedlings subjected to 20 day of water stress was compared to the control. Additionally, Moringa seedlings were grown in the field for 16 months and their growth parameters were evaluated at the end of the experiment. Based on the results, the Moringa seedlings displayed a positive tolerance to water stress. Significant variations were found, such as growth delays in length, reaching up to 30% for the stems and 64% for the roots for ψh = −1.5 MPa. This water potential resulted in a 75% reduction of Relative Growth Rate (RGRh) per day for the water stress experiment (hydroponics), as a reaction of the plant to overcome the stress. Additionally, it had the highest negative effect on stem length and leaf area. As for the plants grown in the field, their main stem height increased by 43.13% and their number of branches by 45.34% per year. An overall (RGRh) of 0.44 per year was noted accompanied by a total phytomass of 0.46 and tree volume of 23.67 g cm−3. Based on the above it can be concluded that Moringa represent a promising species as an ecological solution for use in agroforestry systems, able to minimize the negative effects of drought and to rehabilitate and enhance the soil of arid zones.

The Development of Crassulacean Acid Metabolism (CAM) Photosynthesis in Cotyledons of the C4 Species, Portulaca grandiflora (Portulacaceae).

Portulaca grandiflora simultaneously utilizes both the C4 and Crassulacean acid metabolism (CAM) photosynthetic pathways. Our goal was to determine whether CAM developed and was functional simultaneously with the C4 pathway in cotyledons of P. grandiflora. We studied during development whether CAM would be induced with water stress by monitoring the enzyme activity, leaf structure, JO2 (rate of O2 evolution calculated by fluorescence analysis), and the changes in titratable acidity of 10 and 25 days old cotyledons. In the 10 days old cotyledons, C4 and CAM anatomy were evident within the leaf tissue. The cotyledons showed high titratable acid levels but a small CAM induction. In the 25 days old cotyledons, there was a significant acid fluctuation under 7 days of water stress. The overall enzyme activity was reduced in the 10 days old plants, while in the 25 days old plants CAM activity increased under water-stressed conditions. In addition to CAM, the research showed the presence of glycine decarboxylase in the CAM tissue. Thus, it appears both pathways develop simultaneously in the cotyledons but the CAM pathway, due to anatomical constraints, may be slower to develop than the C4 pathway. Cotyledons showed the ancestral Atriplicoid leaf anatomy, which leads to the question: Could a CAM cell be the precursor to the C4 pathway? Further study of this may lead to understanding into the evolution of C4 photosynthesis in the Portulaca.

Agricultural Policy Environmental eXtender (APEX) Simulation of Spring Peanut Management in the North China Plain

Spring peanut is a valuable alternative crop to mitigate water scarcity caused by excessive water use in conventional cropping systems in the North China Plain (NCP). In the present study, we evaluated the capability of the Agricultural Policy Environmental eXtender (APEX) model to predict spring peanut response to sowing dates and seeding rates in order to optimize sowing dates, seeding rates, and irrigation regimes. Data used for calibration and validation of the model included leaf area index (LAI), aboveground biomass (ABIOM), and pod yield data collected from a field experiment of nine sowing dates and seeding rate combinations conducted from 2017 to 2018. The calibrated model was then used to simulate peanut yield responses to extended sowing dates (5 April to 4 June with a 5-day interval) and seeding rates (15 plants m−2 to 50 plants m−2 with a 5 plants m−2 interval) using 38 years of weather data as well as yield, evapotranspiration (ET), and water stress days under different irrigation regimes (rainfed, one irrigation before planting (60 mm) or at flowering (60 mm), and two irrigation with one time before planting and one time at flowering (60 mm each time) or at pod set (60 mm each time)). Results show that the model satisfactorily simulates pod yield of peanut based on R2 = 0.70, index of agreement (d value) being 0.80 and percent bias (PBIAS) values ≤4%. Moreover, the model performed reasonably well in predicting the emergence, LAI and ABIOM, with a R2 = 0.86, d = 0.95 and PBIAS = 8% for LAI and R2 = 0.90, d = 0.97 and PBIAS = 1% for ABIOM, respectively. Simulation results indicate that the best combination of sowing dates and seeding rates is a density of 35–40 plants m−2 and dates during early-May to mid-May due to the influence of local climate and canopy structure to the growth and yield of peanut. Under the optimal sowing date and plant density, an irrigation depth of 60 mm during flowering gave a pod yield (5.6 t ha−1) and ET (464 mm), which resulted in the highest water use efficiency (12.1 kg ha−1 mm−1). The APEX model is capable of assessing the effects of management practices on the growth and yield of peanut. Sowing 35–40 plants m−2 during early-May to mid-May with 60 mm irrigation depth is the recommended agronomic practice for peanut production in the water-constrained NCP.

Response of sugar metabolism in apple leaves subjected to short-term drought stress

For a comprehensive understanding of gene expression, enzyme activity and sugar concentrations in response to short-term water deficit in apple (Greensleeves), sugar-modulated gene expression and enzyme activities were analyzed. Water stress resulted in the accumulation of sorbitol, glucose, fructose, galactose and starch, accompanied by a significant reduction in photosynthesis and sucrose concentration. In response to short-term water deficits, the activities of aldose-6-phosphate reductase (A6PR; EC 1.1.1.200), sorbitol dehydrogenase (SDH; EC 1.1.1.14), neutral invertase (NINV; EC 3.2.1.26), sucrose synthase (SUSY; EC 2.4.1.13), and fructokinase (FK; EC 2.7.1.4) were higher, whereas cell wall invertase (CWINV; EC 3.2.1.26) and hexokinase (HK; EC 2.7.1.1) activities were lower. In addition, sucrose phosphate synthase (SPS; EC 2.4.1.14) activity increased during the initial stages of dehydration and then decreased as the drought strengthened. Transcript levels of MdA6PR, MdSDH1/2, MdNINV1/2, MdSUSY3, MdFK1/2/4, MdSOT1/2, MdSUC1-3, MdTMT2/3, MdvGT1, MdpGlcT1-4 were upregulated, whereas transcript levels of MdCWINV1/2, MdHK1/2/3/5, and MdTMT1 were downregulated after 6 days of water stress. These findings suggest that the sorbitol metabolism pathway is induced and high levels of hexose derived from photosynthetic products are transported into vacuoles for adjustment to the water deficit. Our results provide insights into the relationships between sugar levels and sugar-modulated gene and enzyme activity in response to the imposition of short-term water stress.

Selection of drought-tolerant rice varieties from the rice variety bank of Can Tho university

Drought has been a big problem and damaged seriously to rice cultivation and production in Vietnam and the Mekong Delta region; evaluating drought tolerance of rice is a major objective for the rice improvement programmes in Can Tho University. Fifty-two collected rice varieties including resistant and susceptible control varieties were screened for water stress under the artificial drought condition. Marker RM223 was used to identify the drought tolerance genotypes for some selected varieties with good and moderate tolerant scores. After 30 days of water stress, the results were 6 varieties of good tolerant, 8 varieties of moderate tolerance, 36 varieties of moderately susceptible and 2 varieties of susceptible to drought. Analyses of PCR showed that 10 varieties expressed the similar bands with the resistant control variety. Four varieties (LH8, MTL812, Lua Canh and VB1) with good tolerant to drought were recommended to use for genetic materials of rice breeding program and applying in alternative wetting and drying irrigation technique for rice cultivation.

Physio-biochemical insights into sugarcane genotypes under water stress

ABSTRACT Sugarcane (Saccharum officinarum L.) is an economic crop cultivated in the tropical and subtropical zones. It is the world’s major crop according to production quantity. Sugarcane crop faces all types of environmental constraints due to its long life cycle period. Among various stresses, water stress creates a major obstacle to sugarcane production. Water deficit during formative stage in sugarcane causes more deleterious effect on crop growth. Plants develop mechanism to perceive external stress signals and adapt by changing in their physiological and biochemical responses. Therefore, this experiment was undertaken to elucidate the changes occur in to physiological and biochemical parameters under water stress in ten sugarcane genotypes. The water stress was applied by water suppression during formative stage (120–150 days). The third fully expanded leaf from random plant of each biological replication was collected on 120th day (irrigated condition), 135th day and 150th day after applying water stress. The obtained results showed significant differences among physio-biochemical responses in all genotypes. Minor fluctuations in physio-biochemical observations were found to be in 15 days of water stress, whereas higher level of percent changes were to be noted in samples of 30 days water stress. A minimum reduction in RWC, MSI, SCMR value, NR activity and higher increase in proline accumulation, catalase, peroxidase activities were found to be in sugarcane genotypes Co 98014, Co 0118, CoPk 05191, Co 0238 and Co 05011. Whereas the genotype Co 89003 and CoJ 64 were more affected in both stress treatment.

Assimilating MODIS data-derived minimum input data set and water stress factors into CERES-Maize model improves regional corn yield predictions.

Crop growth models and remote sensing are useful tools for predicting crop growth and yield, but each tool has inherent drawbacks when predicting crop growth and yield at a regional scale. To improve the accuracy and precision of regional corn yield predictions, a simple approach for assimilating Moderate Resolution Imaging Spectroradiometer (MODIS) products into a crop growth model was developed, and regional yield prediction performance was evaluated in a major corn-producing state, Illinois, USA. Corn growth and yield were simulated for each grid using the Crop Environment Resource Synthesis (CERES)-Maize model with minimum inputs comprising planting date, fertilizer amount, genetic coefficients, soil, and weather data. Planting date was estimated using a phenology model with a leaf area duration (LAD)-logistic function that describes the seasonal evolution of MODIS-derived leaf area index (LAI). Genetic coefficients of the corn cultivar were determined to be the genetic coefficients of the maturity group [included in Decision Support System for Agrotechnology Transfer (DSSAT) 4.6], which shows the minimum difference between the maximum LAI derived from the LAD-logistic function and that simulated by the CERES-Maize model. In addition, the daily water stress factors were estimated from the ratio between daily leaf area/weight growth rates estimated from the LAD-logistic function and that simulated by the CERES-Maize model under the rain-fed and auto-irrigation conditions. The additional assimilation of MODIS data-derived water stress factors and LAI under the auto-irrigation condition showed the highest prediction accuracy and precision for the yearly corn yield prediction (R2 is 0.78 and the root mean square error is 0.75 t ha-1). The present strategy for assimilating MODIS data into a crop growth model using minimum inputs was successful for predicting regional yields, and it should be examined for spatial portability to diverse agro-climatic and agro-technology regions.

The physiological responses of tomato to water stress and re-water in different growth periods

The aim of this study is to investigate the response of physiological functions, and to establish the model between net photosynthetic rate and some other physiological indexes during the eighteen water stress days and the three subsequent re-water days in different growth periods of tomato. Our data showed that the most of the photosynthetic indicators had the decline trend under water stress, and the value under mild water stress was higher than that of moderate water stress at the same growth stage. Furthermore, all of them recovered to the initial value by and large eventually. There was a significant positive linear relationship between net photosynthetic rate and transpiration rate, net photosynthetic rate and stomatal conductance. The instantaneous water use efficiency peaked at the last day of water stress. The activities of superoxide dismutase, peroxidase and catalase in both tomato leaves and roots increased continuously under water stress conditions at three growth stages and recovered a lot after rehydration. According to the results, the superoxide dismutase activities in leaves was higher than in roots and the peroxidase, catalase activities in leaves was lower than in roots throughout the whole growth periods. The value of net photosynthetic rate reduced with the increasing of antioxidant enzyme activities in the whole growth periods, and the correlation between net photosynthetic rate and antioxidant enzyme activities was highly significant. Both the stomatal length and stomatal width had a decline trend which was differ from the stomatal density, stomatal density increased during the water stress days. There was a positive linear correlation between net photosynthetic rate and stomatal length (significant), and significant quadratic relationship between net photosynthetic rate and stomatal width; on the contrary, the negative linear correlation between net photosynthetic rate and stomatal density was highly significant. Although the water stress had negative influences on physiological indicators of tomato, the effects of water stress on physiological indexes was not irreversible, since these indexes had restored to a certain extent after rehydration. The water stress had a bigger impact on physiological parameters in anthesis period than the seedling and fruit expanding period. In conclusion, it was verified that mild water stress had no significant effect compared to the full irrigation on tomato physiological indexes during non-critical growth periods (seedling and fruit expanding period). What’s more, the relationship between net photosynthetic rate and other physiological indexes can be predicted with the data of whole growth period, but it is better to use the data of each growth period for the accurate prediction.

High-resolution imagery acquired from an unmanned platform to estimate biophysical and geometrical parameters of olive trees under different irrigation regimes.

The experiments were conducted in a fully-productive olive orchard (cv. Frantoio) at the experimental farm of University of Pisa at Venturina (Italy) in 2015 to assess the ability of an unmanned aerial vehicle (UAV) equipped with RGB-NIR cameras to estimate leaf area index (LAI), tree height, canopy diameter and canopy volume of olive trees that were either irrigated or rainfed. Irrigated trees received water 4–5 days a week (1348 m3 ha-1), whereas the rainfed ones received a single irrigation of 19 m3 ha-1 to relieve the extreme stress. The flight altitude was 70 m above ground level (AGL), except for one flight (50 m AGL). The Normalized Difference Vegetation Index (NDVI) was calculated by means of the map algebra technique. Canopy volume, canopy height and diameter were obtained from the digital surface model (DSM) obtained through automatic aerial triangulation, bundle block adjustment and camera calibration methods. The NDVI estimated on the day of the year (DOY) 130 was linearly correlated with both LAI and leaf chlorophyll measured on the same date (R2 = 0.78 and 0.80, respectively). The correlation between the on ground measured canopy volumes and the ones by the UAV-RGB camera techniques yielded an R2 of 0.71–0.86. The monthly canopy volume increment estimated from UAV surveys between (DOY) 130 and 244 was highly correlated with the daily water stress integral of rainfed trees (R2 = 0.99). The effect of water stress on the seasonal pattern of canopy growth was detected by these techniques in correspondence of the maximum level of stress experienced by the rainfed trees. The highest level of accuracy (RMSE = 0.16 m) in canopy height estimation was obtained when the flight altitude was 50 m AGL, yielding an R2 value of 0.87 and an almost 1:1 ratio of measured versus estimated canopy height.

Potential impact of future climate change on sugarcane under dryland conditions in Mexico

AbstractAssessments of impacts of future climate change on widely grown sugarcane varieties can guide decision‐making and help ensure the economic stability of numerous rural households. This study assessed the potential impact of future climatic change on sugarcane grown under dryland conditions in Mexico and identified key climate factors influencing yield. The Agricultural Land Management Alternatives with Numerical Assessment Criteria (ALMANAC) model was used to simulate sugarcane growth and yield under current and future climate conditions. Management, soil and climate data from farm sites in Jalisco (Pacific Mexico) and San Luis Potosi (Northeastern Mexico) were used to simulate baseline yields. Baseline climate was developed with 30‐year historical data from weather stations close to the sites. Future climate for three decadal periods (2021–2050) was constructed by adding forecasted climate values from downscaled outputs of global circulation models to baseline values. Climate change impacts were assessed by comparing baseline yields with those in future decades under the A2 scenario. Results indicate positive impacts of future climate change on sugarcane yields in the two regions, with increases of 1%–13% (0.6–8.0 Mg/ha). As seen in the multiple correlation analysis, evapotranspiration explains 77% of the future sugarcane yield in the Pacific Region, while evapotranspiration and number of water and temperature stress days account for 97% of the future yield in the Northeastern Region. The midsummer drought (canicula) in the Pacific Region is expected to be more intense and will reduce above‐ground biomass by 5%–13% (0.5–1.7 Mg/ha) in July–August. Harvest may be advanced by 1–2 months in the two regions to achieve increases in yield and avoid early flowering that could cause sucrose loss of 0.49 Mg ha−1 month−1. Integrating the simulation of pest and diseases under climate change in crop modelling may help fine‐tune yield forecasting.

Differential expression of leaf proteins in four cultivars of peanut (Arachis hypogaea L.) under water stress.

Drought is a major constraint to the productivity of many crops affecting various physiological and biochemical processes. Seventy percent of the peanuts are grown in semiarid tropics that are frequently prone to drought stress. So, we analyzed its effect in 4 cultivars of peanut, with different degrees of drought tolerance, under 10 and 20days of water stress using two-dimensional gel electrophoresis and mass spectrometry. A total of 189 differentially expressed protein spots were identified in the leaf proteome of all the 4 cultivars using PD Quest Basic software; 74 in ICGV 91114, 41 in ICGS 76, 44 in J 11 and 30 in JL 24. Of these, 30 protein spots were subjected to in-gel trypsin digestion followed by MALDI-TOF that are functionally categorized into 5 groups: molecular chaperones, signal transducers, photosynthetic proteins, defense proteins and detoxification proteins. Of these, 12 proteins were sequenced. Late embryogenesis abundant protein, calcium ion binding protein, sucrose synthase isoform-1, 17.3kDa heat shock protein and structural maintenance of chromosome proteins were overexpressed only in the 15 and 20days stressed plants of ICGV 91114 cultivar while cytosolic ascorbate peroxidase was expressed with varying levels in the 10 and 20days stressed plants of all the 4 cultivars. Signaling protein like 14-3-3 and defense proteins like alpha-methyl-mannoside-specific lectin and mannose/glucose-binding lectins were differentially expressed in the 4 cultivars. Photosynthetic protein like Rubisco was down-regulated in the stressed plants of all 4 cultivars while Photosystem-I reaction center subunit-II of chloroplast precursor protein was overexpressed in only 20days stressed plants of ICGV 91114, ICGS 76 and J11 cultivars. These differentially expressed proteins could potentially be used as protein markers for screening the peanut germplasm and further crop improvement.

Rain Water Deficit and Irrigation Demand of Major Row Crops in the Mississippi Delta

Abstract. The Mississippi Delta is an important agricultural area, producing 67% of the soybean, corn, and cotton grown in the state of Mississippi. Because irrigation can stabilize and increase crop yields and economic returns, approximately 80% of the water withdrawn from the alluvial aquifer is used for irrigation. This region is experiencing severe declines in groundwater level, which threaten the sustainability of irrigated agriculture. Therefore, better irrigation management practices must be developed, but there is lack of knowledge regarding crop water requirements, rain water deficits, and irrigation demand to improve rain and irrigation water use efficiencies of these crops. The objective of this study was to determine the crop water requirements, rain water deficits, and irrigation demand of the three crops using the RZWQM2 model based on a 100-year representative weather data series from the Stoneville weather station for improving irrigation management in the Mississippi Delta. The analysis indicated that mean monthly precipitation in the crop non-growing season from November to the following April was 127 mm, while only 82 mm on average was received during the crop growing season. Soybean, corn, and cotton are typically planted in early May, late March, and late May and harvested in mid-September, late August, and late October, respectively. Rainfall during the growing seasons for soybean, corn, and cotton was 400, 510, and 435 mm and accounted for 31%, 40%, and 34% of annual rainfall, respectively, over the 100-year period. Early seeding can allow crops to receive more early season rainfall and reduce the number of days of water stress during the growing season. Average crop evapotranspiration of soybean, corn, and cotton was 546, 588, and 552 mm, respectively. Rainfall was found to be insufficient to meet the crop water requirements beginning in the 5th, 7th, and 6th weeks after planting. Weekly effective rain water deficits greater than 20 mm were found in weeks 7 through 16 (22 to 29 mm) for soybean, in weeks 11 through 20 (20 to 26 mm) for corn, and in weeks 11 through 16 (20 to 30 mm) for cotton. The RZWQM2 model estimated a range of annual effective rain water deficits in soybean of 0 to 622 mm, with an average deficit of 340 mm. Deficits in corn ranged from 32 to 685 mm, with an average deficit of 355 mm, while deficits in cotton ranged from 169 to 650 mm, with an average deficit of 395 mm. Results obtained from the 100-year historical weather data can be applied to improve irrigation scheduling, water resources planning, and design of irrigation and cropping systems in the Mississippi Delta. Keywords: Corn, Cotton, Crop water requirement, Irrigation demand, Mississippi Delta, Rain water deficit, Soil water balance, Soybean.

Preliminary Variations in Physiological Modules When <i>sub</i>1<i>A</i> QTL Is under Soil-Moisture Deficit Stress

The present investigation embodies with some distinct physiological responses of rice seedlings bearing sub1A allele when cultured under soil moisture deficit condition. In order to estimate the extent of variation of sub1A allele in cv. Swarna Sub1, few specific responses were recorded. Ongoing days (2, 4 and 8) of water stress, rice seedlings were mostly concerned with regulation of root growth through 1.24%, 4.10% and 8.96% as compared to control. When relative growth rate (RGR) of the biomass was considered, it recorded a significant down regulation maximum by 27.27% over non-stressed plants. The light absorbing capacity of foliages in terms of leaf mass ratio (15.62%) and specific leaf weight (8.45%) was also curtailed under stress contiguously with total dry matter accumulation. For light harnessing mechanism, the contributing pigments were most significantly (p ≤ 0.05) affected with maximum variation for chlorophyll (31.29%), lycopene (79.31%) and carotenoids (55.31%) over control. NAR was strikingly differed by 32.72% under water stress in average. To support the water stress related depletion of moisture tension, plants recorded RWC with a ranges of 6.62% to 21.57% under stress than control. In balance of cellular dehydration rice seedlings were recorded 6.72% loss of proline, but up-regulated the release of free amino acids by 1.35 fold. In expression of generic potential for sub1A allele, the growth inhibition even under water deficit was evident from carbohydrate depletion by 10.93%, 11.42% and 24.35% through days of treatments. This was supported by depletion of apoplastic and cellular invertase activities by 90.90% and 72.91%. The possibility for sub1A in tolerance of deficit water status in rice culture has been discussed in more details.

Least limiting water range for oil palm production in Amazon region, Brazil

In areas cultivated with oil palm, typically mechanized field operations using heavy vehicles may negatively affect soil physical properties and productivity. The aim of this study was to evaluate soil physical quality in an area cultivated with oil palm by monitoring the temporal variation of the soil water content and relating it to the critical limits of the least limiting water range. Soil bulk density (Bd), soil penetration resistance (SR), least limiting water range (LLWR), and water stress days (WSD) were used to assess soil physical quality in planting rows (PR) and the traffic zone (TZ) at depths 0-20, 20-40, and 40-60 cm. The Bd was higher and the LLWR was reduced in TZ only at the surface layer. The effect of temporal variation in soil water content on the soil physical quality was higher in TZ, mainly in subsurface layers. Bd and LLWR did not affect the fresh fruit bunch production; however, WSD in TZ at 20-40 and 40-60 cm layers provided evidence of effects of temporal variation of soil water content on oil palm productivity.

Nitrogen Use and Protein Yield of Two Maize Cultivars in Cohesive Tropical Soil

One major challenge to developing sustainable family farms in tropical regions is increasing nitrogen use efficiency. The aim of this study was to evaluate the combined effects of leguminous residues of low-and high-quality on nitrogen uptake, as well as on content of protein of a Quality Protein Maize (QPM) and of a hybrid maize in a tropical sandy loam soil. The experimental design consisted of randomized blocks with four replicates in a 6 × 2 factorial and six treatments: Gliricidia + Clitoria (GC); Gliricidia + Acacia (GA); Leucaena + Gliricidia (LG); Leucaena + Clitoria (LC); Leucaena + Acacia (LA) and a control without legumes (C). A sub-plot was constructed, sowing in each plot two maize cultivars, opened pollination QPM BR 473 and hybrid Ag 7088. We conclude that the combined use of leguminous residues applied on the soil surface might increase the uptake of nitrogen, the protein contents of maize and the grain yield. In bare soil prone to cohesion, the use of synthetic N is not feasible for both maize yield and for protein yield compared with use of covered soil. The results also showed that the effects of leguminous residue quality on N uptake may differ from year to year due to variation in water stress days.

Water stress indices for the sugarcane crop on different irrigated surfaces

ABSTRACT Sugarcane (Saccharum officinarum L.) is a crop of vital importance to Brazil, in the production of sugar and ethanol, power generation and raw materials for various purposes. Strategic information such as topography and canopy temperature can provide management technologies accessible to farmers. The objective of this study was to determine water stress indices for sugarcane in irrigated areas, with different exposures and slopes. The daily water stress index of the plants and the water potential in the soil were evaluated and the production system was analyzed. The experiment was carried out in an “Experimental Watershed”, using six surfaces, two horizontal and the other ones with 20 and 40% North and South exposure slopes. Water stress level was determined by measuring the temperatures of the vegetation cover and the ambient air. Watering was carried out using a drip irrigation system. The results showed that water stress index of sugarcane varies according to exposure and slope of the terrain, while areas whose water stress index was above 5.0 oC had lower yield values.

Expression of NCED gene in colored cotton genotypes subjected to water stress

ABSTRACT Considering that the NCED gene acts on the biosynthetic cascade of ABA, a hormone involved in the functioning of stomata and consequently in the regulation of transpiration, the aim of this research was to analyze the expression of this gene in colored cotton genotypes subjected to water stress at the beginning of plant growth. Four colored cotton genotypes were used, subjected to two managements, with and without water stress, beginning the treatments when the blade of the first true leaves reached an area that allowed the evaluation of gas exchange. For the studies of the expression of the NCED gene, via RT-qPCR, leaves were collected on three distinct dates: at 4 and 6 days of water stress, and after the plants regained their turgor. The differential expression of NCED was found in all genotypes, with higher levels of expression related to six days of water stress. When the stomatal conductance was around 25%, there was overexpression in the genotype CNPA 2009.13, followed by CNPA 2009.6, BRS SAFIRA and CNPA 2009.11, confirming the data obtained in the semi-quantitative RT-PCR. The NCED gene is involved in the response to water stress in the vegetative phase of colored cotton.