Contrasting Moisture Regimes Research Articles

Growing at the arid edge: Anatomical variations in leaves are more extensive than in stems of five Mediterranean species across contrasting moisture regimes.

Increasing aridity in the Mediterranean region affects ecosystems and plant life. Various anatomical changes in plants help them cope with dry conditions. This study focused on anatomical differences in leaves and xylem of five co-occurring Mediterranean plant species namely Quercus calliprinos, Pistacia palaestina, Pistacia lentiscus, Rhamnus lycioides, and Phillyrea latifolia in wet and dry sites. Stomatal density, stomatal length, leaf mass area, lamina composition, percentage of intercellular air spaces, and mesophyll cell area in leaves of plants in wet and dry sites were analyzed. Xylem anatomy was assessed through vessel length and area in branches. In the dry site, three species had increased stomatal density and decreased stomatal length. Four species had increased palisade mesophyll and reduced air space volume. In contrast, phenotypic changes in the xylem were less pronounced; vessel length was unaffected by site conditions, but vessel diameter decreased in two species. Intercellular air spaces proved to be the most dynamic anatomical feature. Quercus calliprinos had the most extensive anatomical changes; Rhamnus lycioides had only minor changes. All these changes were observed in comparison to the species in the wet site. This study elucidated variations in anatomical responses in leaves among co-occurring Mediterranean plant species and identified the most dynamic traits. Understanding these adaptations provides valuable insights into the ability of plants to thrive under changing climate conditions.

Field identification of drought tolerant wheat genotypes using canopy vegetation indices instead of plant physiological and biochemical traits

Seasonal drought is a major limiting factor for wheat production in the North China Plain. The use of non-destructive screening tools based on vegetation indices associated with physiological and biochemical traits will help in the identification of drought-tolerant wheat genotypes to counter drought stress. The objectives of this study were to characterize the performance of 10 wheat genotypes with different genetic backgrounds in terms of physical and biochemical traits under two contrasting moisture regimes, and to evaluate the effectiveness of vegetation indices/spectral measurement techniques for assessing drought tolerance in wheat. Traits associated with drought stress were assessed in the 10 wheat genotypes, including plant biophysical parameters, drought tolerance parameters, as well as various vegetation indices. Significant variability was found wheat genotypes with different genetic backgrounds to water stress. The clustering results indicated that Luohan-19, Luohan-22, and Jinmai-47 were drought-tolerant genotypes characterized by high stress tolerance index (STI) values (0.548, 0.535 and 0.523, respectively), drought index (DI) values (0.517, 0.524 and 0.504, respectively), and drought tolerance coefficient (DC) values (1.065, 1.074 and 1.000, respectively). Based on principal component analysis and membership function, genotypes were classified as tolerant (Luohan-19, Luohan-22, and Jinmai-47), moderately tolerant (Luomai-26, Zhongmai-175, and Bainong-207) and sensitive (Yunong-516, Zhongmai-895, Annong-0711 and Huacheng-3366) to water stress, with comprehensive evaluation values (D) of >0.761, 0.422–0.761, and <0.422, respectively. Heatmap analysis of various vegetation indices for screening wheat genotypes showed similar results to the multivariate data analysis; that is, genotypes Luohan-19, Luohan-22, and Jinmai-47 were identified as drought-tolerant genotypes. Among these vegetation indices, the normalized difference water index (NDWI) and the red edge chlorophyll index (CIred edge) were highly correlated with the drought tolerance indices, such as STI and DI (r2 >0.717), and are therefore recommended as rapid indicators for the identification of tolerance genotypes in the field. These vegetation indices, particularly NDWI and CIred edge, exhibited similar performance to the drought tolerance indices and multivariate data analysis results in identifying drought-tolerant genotypes, and thus they can be used as alternative and inexpensive measures for identifying drought tolerance in wheat in the future.

Trait responses of a grassland shrub invader to altered moisture regimes

PurposeWe sought to identify plant traits important for initial establishment of a globally invasive shrub, Prosopis spp. (mesquite), by quantifying morphological and ecophysiological responses of seedlings to contrasting moisture regimes. Our model plant was Prosopis velutina, a prominent invader of North American semi-desert grasslands.MethodsSeedlings received one of three watering levels corresponding to regional ‘ambient’ (100%), ‘dry’ (−65%; 65% reduction of ambient), and ‘wet’ (+165%; 65% increase above ambient) growing season precipitation regimes. A total of 32 plant performance (e.g., biomass and growth) and functional (e.g., morphological and physiological) traits were assessed when seedlings reached 11- and 22-days old.ResultsGermination under dry conditions was high (72%) and only slightly reduced compared to ambient and wet conditions with subsequent seedling survival unaffected. High trait variation enabled early recruitment over the range of soil moisture conditions, including extreme drought. Root volume, surface area, tips, tap root length, and leaf length functional traits were top predictors of seedling performance, with fresh weight, absolute growth rate, and root mass secondarily contributing to establishment.ConclusionNo physiological functional traits were significant in predicting performance or discriminating between moisture regimes; suggesting morphological traits for maintaining metabolic and hydraulic function are key to early establishment. Dry conditions reduced germination and slowed P. velutina seedling growth but did not prevent early establishment. Thus, recruitment of certain dryland shrubs may not be episodic with respect to above-average rainfall. Indeed, early recruitment of P. velutina and functionally similar species can potentially occur even in moisture conditions well below-average.

Nitrogen Release in Soils Amended with Different Organic and Inorganic Fertilizers under Contrasting Moisture Regimes: A Laboratory Incubation Study

Understanding nitrogen (N) release patterns and kinetics is a key challenge for improving N use efficiency in any agroecosystem. An incubation experiment was done to study the N release pattern and kinetics of contrasting soils amended with compost (CO), poultry manure (PM), rice husk biochar (RHB), poultry manure biochar (PMB) and cowdung (CD) combined with chemical fertilizer (integrated plant nutrient system, IPNS approach) under two moisture regimes, viz. field capacity (FC) and continuous standing water (CSW) at 25 °C for 120 days. Our results revealed that NH4+-N was the dominant under CSW conditions, whereas NO3−-N was dominant under FC conditions. Net mineral N data fitted well to the first order kinetic model. Both N release potential (N0) and rate constant (k) were greater in acidic soil than those of charland soil. The maximum N release varied between 24.90–76.29% of input depending on soil type and moisture status. N mineralization was strongly correlated with urea N application. PM and PMB mineralized in all soil and moisture conditions whereas N immobilization was observed in the case of RHB. N mineralization was strongly correlated with urea N application. Gaseous N losses were different for the organic amendments exhibiting more gaseous N losses in PM, CD and CO based IPNS whereas the lowest gaseous N loss was observed in PMB based IPNS. Biochar based IPNS increased soil pH in all conditions. Thus, the present study suggests that N release depends on soil type, soil moisture and type of organic amendment. However, CO, PM and CD based IPNS can be recommended for both acidic and charland soils in terms of N release as short duration crops will suffer from N deficiency if biochar based IPNS is used in the field.

Genetic studies for drought tolerance under contrasting moisture regimes in rice (Oryza sativa L.)

Twenty six genotypes and four check varieties were studied for drought tolerance in rice. The experiment was conducted under both irrigated and stress regimes. Ten different drought tolerant contributing traits were evaluated under stress regime and five yield contributing traits were evaluated under irrigated regime. Among the studied genotypes, IR 87651-26-1-1-3 possessed desirable mean performance under stress for grain yield with other studied traits except number of panicles per plant. Under irrigated regime, the genotypes IR 87753-13-1-1-3, IR 87638-10-1-1-3, IR 87759-5-2-1-3 and IR 83381-B-B-137-3 were advantageous for grain yield and other studied traits except number of panicles per plant. From the variability studies under stress, the traits viz., leaf rolling, leaf senescence, leaf drying, panicle exsertion and grain yield exhibited high genetic advance indicated additive gene action and selection is desirable for these traits. High heritability with advantageous genetic advance was recorded for plant height and grain yield under non-stress regime. From the association analysis, grain yield had positive correlation with plant height, number of panicles per plant and panicle length and negative correlation with days to fifty per cent flowering, leaf rolling, leaf senescence, leaf drying and panicle exsertion under stress. Grain yield was positively correlated with days to fifty per cent flowering, plant height and panicle length under non stress. The desirable genotypes recognized from this study may be utilized as donors and the desirable traits identified may be exploited for drought tolerance rice breeding programs.

Evaluation of nutritional and phytochemical variability of cowpea Recombinant Inbred Lines under contrasting soil moisture conditions in the Guinea and Sudan Savanna Agro-ecologies

Plant breeders’ efforts in developing drought tolerant and high-yielding cowpea varieties may be in vain unless the developed varieties are evaluated to ascertain the influence of water stress on their nutritive value, antioxidants, and phenolic contents under contrasting moisture regimes. The study was set up to evaluate the nutritional value, phytochemical content and antioxidant activity of cowpea Recombinant Inbred Lines (RILs) under contrasting soil moisture in the Guinea and Sudan Savanna agro-ecologies of Ghana. Forty-eight cowpea RILs seed samples from well-watered and water stress experiment were pulverized. Distillation and titration was carried out and the organic samples extracted and various biochemical analyses were carried out using standard protocols and methodologies. The dried grain mineral contents were determined using an Atomic Absorption Spectrophotometer, while the protein content was determined by the combustion method. Correlation and regression analysis and principal component analysis were performed using STATA version 13. Biochemical analysis for seed related traits revealed that inbred lines responded differently to drought. Significant differences of watering regimes on various phytochemical traits were only observed in phosphorus and lead. Inbred line with family number 57 had the highest crude protein content of 46.90% under well-watered conditions. Inbred line 84 under water stress conditions had high levels of Mg and K. Inbred line 20 under well-watered conditions had the highest antioxidant content. For phenolic acid content, inbred line 255 scored the highest. Quercetin and rutin were most abundant in inbred line 186 for both water-stress and well-watered conditions. The indication is that moisture stress could affect seed yield but no effects on the phytochemical and nutritional variables. Genotypic differences could arise from parental combination used for developing the inbred lines for the study.

Non-rainfall Moisture: A Key Driver of Microbial Respiration from Standing Litter in Arid, Semiarid, and Mesic Grasslands

Models assume that rainfall is the major moisture source driving decomposition. Non-rainfall moisture (NRM: high humidity, dew, and fog) can also induce standing litter decomposition, but there have been few measurements of NRM-mediated decomposition across sites and no efforts to extrapolate the contribution of NRM to larger scales to assess whether this mechanism can improve model predictions. Here, we show that NRM is an important, year-round source of moisture in grassland sites with contrasting moisture regimes using field measurements and modeling. We first characterized NRM frequency and measured NRM-mediated decomposition at two sites in the Namib Desert, Namibia (hyper-arid desert), and at one site in Iowa, USA (tallgrass prairie). NRM was frequent at all sites (85–99% of hours that litter was likely to be wet were attributed to NRM) and tended to occur in cool, high-humidity periods for several hours or more at a time. NRM also resulted in CO2 release from microbes in standing litter at all sites when litter became sufficiently wet (> 5% gravimetric moisture for fine litter and > 13% for coarse), and significantly contributed to mass loss, particularly in the western Namib site that received almost no rain. When we modeled annual mass loss induced by NRM and rain and extrapolated our characterization of NRM decomposition to a final semiarid site (Sevilleta, New Mexico), we found that models driven by rainfall alone underestimated mass loss, while including NRM resulted in estimates within the range of observed mass loss. Together these findings suggest that NRM is an important missing component in quantitative and conceptual models of litter decomposition, but there is nuance involved in modeling NRM at larger scales.Specifically, temperature and physical features of the substrate emerge as factors that affect the microbial response to litter wetting under NRM in our sites, and require further study. Hourly humidity can provide an adequate proxy of NRM frequency, but site-specific calibration with litter wetness is needed to accurately attribute decomposition to periods when NRM wets litter. Greater recognition of NRM-driven decomposition and its interaction with other processes like photodegradation is needed, especially since fog, dew, and humidity are likely to shift under future climates.

Emmer wheat (Triticum dicoccon Schrank) improves water use efficiency and yield of hexaploid bread wheat

Emmer wheat (Triticum dicoccon Schrank) is a potential source of new genetic diversity for the improvement of hexaploid bread wheat. Emmer wheat was crossed and backcrossed to bread wheat and 480 doubled haploids (DHs) were produced from BC1F1 plants with hexaploid appearance derived from 19 crossses. These DHs were screened under well-watered conditions (E1) in 2013 to identify high-yielding materials with similar phenology. One-hundred and eighty seven DH lines selected on this basis, 4 commercial bread wheat cultivars and 9 bread wheat parents were then evaluated in extensive field experiments under two contrasting moisture regimes in north-western NSW in 2014 and 2015. A significant range in the water-use-efficiency of grain production (WUEGrain) was observed among the emmer derivatives. Of these, 8 hexaploid lines developed from 8 different emmer wheat parents had significantly improved intrinsic water-use-efficiency (WUEintr) and instantaneous water-use-efficiency (WUEi) compared to their bread wheat recurrent parents. Accurate and large scale field-based phenotyping was effective in identifying emmer wheat derived lines with superior performance to their hexaploid bread wheat recurrent parents under moisture stress.

Genetic response of diverse sunflower genotypes in contrasting moisture regimes for various physiological and growth parameters at early developmental stage

Abstract Sunflower has great capacity for bridge the edible oil gap in Pakistan. It ranks second to soybean in worldwide vegetable oil production. A greenhouse experiment was performed in the research area of Department of Plant Breeding and Genetics, University of Agriculture, Faisalabad. Eleven (11) advanced lines along with Hysun-37 (Check) were evaluated under complete randomized design (CRD) replicated thrice for two water regimes and three harvestings at early developmental stage. Different morphological and physiological plant traits were recorded to find out genetic analysis of water stress tolerance in sunflower. Results for analysis of variance exhibited significantly differences among all sunflower genotypes for all the traits. Genotypes performed different under contrasting water regimes. Genotypes like A-25, A-50 and A-57 performed best under both normal and water stress condition due to increased shoot length, deep rooting pattern, increased number of root branches and possessing enormousmass of fresh and dry shoot and root traits. Presence of these enviable plant traits make them superior among all genotypes in comparison with hybrid variety. Correlation analysis indicated strong genotypic and phenotypic correlation between shoot length and shoot dry weight. Traits that possessed significant positive phenotypic correlation with shoot length were dry root weight and fresh root weight. Stress tolerant genotypes viz. A-25, A-50 and A-57 could be recommended for utilization in future sunflower breeding program and can be grown under water stress conditions for high yield. Keywords: Correlation; Genetic variability; Seedling traits; Sunflower http://dx.doi.org/10.19045/bspab.2019.80024

The Effect of Contrasting Moistening Regimes on CO2 Emission from the Gray Forest Soil under a Grass Vegetation and Bare Fallow

The effect of contrasting moisture regimes on the CO2 emission from the gray forest soils (Haplic Luvisols (Loamic, Cutanic, Humic)) under a grass vegetation and bare fallow was studied in a field simulation experiment in June–September, 2015 (Moscow region). Two short soil droughts (53 and 34 days) and a long one (94 days) were simulated on plots isolated from precipitation. A variant with regular irrigation, where the soil moisture was maintained 60–70% of their water holding capacity, was used as a control. Over the whole observation period, the CO2 emissions from the soils studied decreased by a factor of 1.8 compared to the control only in the variant with the grass vegetation under prolonged drought. During the first hours after irrigation of the dry plots, the soil respiration intensified due to the “Birch effect”. The magnitude of this effect was 84–104% in the soils under the grass vegetation and 114–133% in the fallow areas. Owing to this phenomenon, the total CO2 emission from the soils subjected to two short droughts was equal to the CO2 flux under regular moistening for the grass plots and exceeded it by almost 1.3 times for the fallow plots as compared to the control. However, the share of extra CO2 flux induced by moistening of the dry soils did not exceed 8–10% of the total CO2 emission over the whole observation period.

Divergent Patterns of Selection on Crassulacean Acid Metabolism Photosynthesis in Contrasting Environments

Premise of research. Crassulacean acid metabolism (CAM), a photosynthetic pathway that evolved in response to aridity, is beneficial for plant species in arid and semiarid environments, with positive effects on plant fitness. However, since it implies a higher metabolic cost compared with that for C3 plants, its expression under moist conditions, where it might be less necessary, could have fewer positive or even negative effects on plant fitness. Variations of the effects of CAM expression under different moisture regimes have never been addressed. Our objectives were to determine whether there are such variations and, if so, their possible ecological and evolutionary implications.Methodology. We measured CAM expression (as nocturnal acidification, ∆H+) and moisture-related morphological leaf traits, estimating their impact on reproductive effort in two populations of Puya chilensis living under contrasting moisture regimes in a natural climatic gradient in central Chile. To evaluate the effects of the measured traits on fitness, a phenotypic selection analysis was performed.Pivotal results. Phenotypic selection analysis showed that ∆H+ was the only trait significantly associated with relative fitness in both populations. There is a significant “switch” in the direction of selection between both studied populations: directional selection on CAM was positive in the dry population and negative in the moist population.Conclusions. Results suggest that under moist regimes the expression of CAM by P. chilensis could be removed by natural selection. To our knowledge, this is the first report of a negative effect of CAM on plant fitness. Since CAM is not usually studied in moist environments, we believe this pattern might be more frequent than expected. Further research on this issue is needed, especially in the context of current climate change.

Impact of decade-long warming, nutrient addition and shading on emission and carbon isotopic composition of CO2 from two subarctic dwarf shrub heaths

This study investigated ecosystem respiration, soil respiration and carbon isotopic composition in CO2 emitted from two subarctic shrub heaths with contrasting moisture regimes. The reported measurements were conducted 22 years (mesic heath) and 12 years (wet heath) upon initiation of in situ climate change related manipulations of temperature, nutrient availability and light.The aim was to quantify expected climatic change effects on soil and ecosystem respiration, and to investigate whether the emitted CO2 originates from old carbon stores in the soil or from newly fixed carbon. Ecosystem and soil respiration was measured using closed chambers and CO2 in the soil profile was sampled with gas probes installed at different depths.At the mesic heath ecosystem respiration was increased 46% by warming while soil respiration increased 133% by nutrient addition. At the wet heath, warming increased ecosystem respiration by 99% and soil respiration by 58%. Litter addition, short time warming and shading generally did not change ecosystem- and soil respiration.The carbon isotope compositions of the sources to CO2 were not significantly altered by any of the treatments at the two heaths across the growing season. However, there was a tendency across growing season towards an increased δ13C source value after 22 years of warming in the mesic shrub heath, and the effect was statistically significant in June, indicating increased decomposition of 13C enriched material. Hence, although more of the old carbon stock in the soil was possibly mineralized under warmed conditions, indicating a risk of long lasting positive feedback on climate warming, the effect was only periodically strong enough to gain statistical significance, despite strong warming-induced effect on ecosystem respiration, and may be counteracted by increased C gain by higher primary production.

Genome-Wide Association Study for Plant Height and Grain Yield in Rice under Contrasting Moisture Regimes.

Drought is one of the vitally critical environmental stresses affecting both growth and yield potential in rice. Drought resistance is a complicated quantitative trait that is regulated by numerous small effect loci and hundreds of genes controlling various morphological and physiological responses to drought. For this study, 270 rice landraces and cultivars were analyzed for their drought resistance. This was done via determination of changes in plant height and grain yield under contrasting water regimes, followed by detailed identification of the underlying genetic architecture via genome-wide association study (GWAS). We controlled population structure by setting top two eigenvectors and combining kinship matrix for GWAS in this study. Eighteen, five, and six associated loci were identified for plant height, grain yield per plant, and drought resistant coefficient, respectively. Nine known functional genes were identified, including five for plant height (OsGA2ox3, OsGH3-2, sd-1, OsGNA1, and OsSAP11/OsDOG), two for grain yield per plant (OsCYP51G3 and OsRRMh) and two for drought resistant coefficient (OsPYL2 and OsGA2ox9), implying very reliable results. A previous study reported OsGNA1 to regulate root development, but this study reports additional controlling of both plant height and root length. Moreover, OsRLK5 is a new drought resistant candidate gene discovered in this study. OsRLK5 mutants showed faster water loss rates in detached leaves. This gene plays an important role in the positive regulation of yield-related traits under drought conditions. We furthermore discovered several new loci contributing to the three investigated traits (plant height, grain yield, and drought resistance). These associated loci and candidate genes significantly improve our knowledge of the genetic control of these traits in rice. In addition, many drought resistant cultivars screened in this study can be used as parental genotypes to improve drought resistance of rice by molecular breeding.

Identification of most important rice root morphological markers in response to contrasting moisture regimes under vegetative stage drought

The experiment was carried out to examine the effect of moisture stress (drought) on different root traits, rooting pattern and to identify important root morphological markers contributing to stress tolerance. Moisture stress was imposed on 21 days old seedlings of selected rice genotypes grown in PVC cylinders. Samplings were done at 10 and 20 days after imposition of stress to examine the effect of stress on root growth and development. Results revealed that rate of assimilate allocation impeded more under 20 days stress (severe) than in 10 days stress (moderate) in terms of enhanced root: shoot ratio, maximum root length to shoot length ratio and root volume. Magnitude of trait variation among genotypes was more pronounced under severe stress than under moderate stress. The root: shoot ratio, maximum root length to shoot length ratio and root volume were observed to be the most crucial morphological markers in determining drought tolerance in rice genotypes analyzed through biplot analysis. Among the thirteen genotypes tested, AC-42994, AC-42997, AC-43020, CR-143-2-2, Ronga Bora and Bora were found to possess desirable root traits and these genotypes can be used in the breeding programme for enhancing drought tolerance in rice.

The genetic basis of spectral reflectance indices in drought-stressed wheat

Drought imposes a major constraint over the productivity of wheat, particularly in arid and semi-arid production zones. Here, the genetic basis of spectral reflectance indices was investigated in drought-stressed wheat by comparing, under two contrasting moisture regimes, the performance of an F6 recombinant inbred line (RIL) population bred from a cross between the drought tolerant cultivar Pavon76 and the sensitive cultivar Yecora Rojo. The parents and RILs were genotyped with respect to both a set of microsatellite (SSR) loci and a number of known drought-responsive genes. In all, 28 quantitative trait loci (QTL) controlling dry weight per plant, water content of the above-ground biomass, leaf water potential, canopy temperature, and spectral reflectance indices traits were identified. The loci were distributed over 11 chromosomes, belonging to each of the three wheat sub-genomes. There were important location-flanking markers Barc109 and Barac4 on chromosome 5B relating to dry weight per plant accumulation under the limited irrigation regime. The same region-harbored QTL associated with leaf water potential, canopy temperature, and ratio index under the limited irrigation regime. Linkage between the known drought-responsive genes and aspects of the drought response was established. Some of QTL were of substantial enough effect for their linked markers to be likely usable for the marker-assisted breeding of drought tolerance in wheat.

Evaluation of common bean (Phaseolus vulgaris L.) genotypes for drought stress adaptation in Ethiopia

Drought stress linked with climate change is one of the major constraints faced by common bean farmers in Africa and elsewhere. Mitigating this constraint requires the selection of resilient varieties that withstand drought threats to common bean production. This study assessed the drought response of 64 small red-seeded genotypes of common bean grown in a lattice design replicated twice under contrasting moisture regimes, terminal drought stress and non-stress, in Ethiopia during the dry season from November 2014 to March 2015. Multiple plant traits associated with drought were assessed for their contribution to drought adaptation of the genotypes. Drought stress determined by a drought intensity index was moderate (0.3). All the assessed traits showed significantly different genotypic responses under drought stress and non-stress conditions. Eleven genotypes significantly (P≤0.05) outperformed the drought check cultivar under both drought stress and non-stress conditions in seed yielding potential. Seed yield showed positive and significant correlations with chlorophyll meter reading, vertical root pulling resistance force, number of pods per plant, and seeds per pod under both soil moisture regimes, indicating their potential use in selection of genotypes yielding well under drought stress and non-stress conditions. Clustering analysis using Mahalanobis distance grouped the genotypes into four groups showing high and significant inter-cluster distance, suggesting that hybridization between drought-adapted parents from the groups will provide the maximum genetic recombination for drought tolerance in subsequent generations.

Analysis of Interrelationships of Phenological and Morphological Traits and Grain Yield of Brassica Species under Contrasting Moisture Regimes

Analysis of Interrelationships of Phenological and Morphological Traits and Grain Yield of Brassica Species under Contrasting Moisture Regimes

Indirect monitoring of root activity in soybean cultivars under contrasting moisture regimes by measuring electrical capacitance

The applicability of root electrical capacitance (EC) measurement for in situ investigation of root activity and drought tolerance was tested in soybean cultivars. Well-watered and drought-stressed plants were grown in pots with repeated EC measurements, followed terminally by harvest to determine root dry mass (RDM), shoot dry mass (SDM), root/shoot ratio (RSR) and leaf area (LA). EC measurement showed the cultivar differences in root growth and biomass production. EC increased till the beginning of flowering, then became nearly constant. Terminal EC was highly correlated with RDM for non-stressed (R 2 = 0.844) and stressed plants (R 2 = 0.936). Drought reduced the EC of cultivars by 28.8–50.5 %, consistently with the corresponding changes of SDM (25.5–49.1 %) and LA (23.6–51.5 %), but considerably exceeded the loss of RDM (12.6–47.3 %) in some cultivars. The reason is drought increased the RSR (by 3.9–21.9 %), leading to decreased water uptake, and thus EC per unit of RDM. This was confirmed by the significantly decreased slope of EC–RDM regression line from 0.437 to 0.317 nF g−1 RDM calculated for well-watered and drought-stressed plants, respectively. As EC referred to root uptake activity, it was better indicator of the actual root status than RDM. EC measurement was adequate for monitoring the cultivar-specific differences in root growth and for estimation of biomass loss caused by drought. By supplementing the conventional methods, this in situ technique could be useful for various fields of agriculture, including cultivar selection or stress tolerance studies.

Accumulation of Reserve Compounds in Common Bean Seeds under Drought Stress

To investigate the seed protein and major mineral nutrient (Fe, Zn, P, and N) contents and their accumulation procedure in the seeds of common bean (Phaseolus vulgaris L.), a biennial experiment was conducted under two contrasting moisture regimes (normal irrigation and water deficit). Seed reserves of eight genotypes (WA4502-1, WA4531-17, Akhtar, D81083, AND1007, KS21486, MCD4011, and COS16) were investigated at four stages of seed filling period (SFP). Split-plot experiments were performed as randomized complete block design with four replications. The results showed significant differences in the evaluated characteristics in both factors, the genotypes and the moisture regimes. Fe content of the seeds was affected the most by drought stress and reduced in all stages, while seed nitrogen and protein contents were affected the least under stress condition. The percentages of reductions due to water deficit were higher in stage 1 for Fe, stage 2 for Zn, and stage 4 for P and N. In the stage 3, minerals had the least changes. Nitrogen content of the seeds at mid-stages of SFP increased slightly under drought stress. Drought stress also caused 39–69% reductions in the grain yield of the genotypes. Under drought stress condition, the concentrations of Fe and N in the white bean seeds were less than that of the red and the Chitti genotypes. However, the seed P contents of the white bean seeds were higher than that of the other genotypes.

Heritability, Correlation and Path Analysis among Yield and Yield Attributing Traits for Drought Tolerance in an Interspecific Cross Derived from &lt;i&gt;Oryza sativa x O. glaberrima &lt;/i&gt;Introgression Line under Contrasting Moisture Regimes

Drought is a major constraint for rainfed lowland and upland rice productivity throughout world. A backcross inbred population derived from ‘Swarna’ and ‘WAB450-I-B-P-157-2-1’ (Oryza sativa L. x O. glaberrima) was evaluated under both irrigated and lowland drought stresses for yield and yield related traits across three different seasons. Significant differences were found among all the analyzed traits. Coefficients of variation were recorded relatively high for filled grains per panicle, spikelet fertility, test weight, harvest index and grain yield and low for panicle length under both conditions during the study interval. Broad sense heritability varied from 0.28 (panicle number) to 0.83 (plant height) under stress and 0.31 (test weight) to 0.86 (plant height) under control. However, heritability estimates for grain yield and harvest index were found to be similar under both conditions. Traits such as filled grains per panicle, spikelet fertility, harvest index and grain yield recorded higher values of both heritability, as well as genetic advance under both conditions, indicating the suitability of these traits as selection criteria to derive high yielding genotypes for drought prone regions. Harvest index exhibited maximum positive direct effect on grain yield under both the conditions; in addition, filled grains per panicle, spikelet fertility and biomass had positive direct effect on grain yield under both irrigated and lowland drought stresses state. Hence, for improving the rice yield under lowland drought ecology, a genotype should posses a large number of panicles per plant, filled grains per panicle, high spikelet fertility and maintains higher biomass and harvest index.