Differences between soybean genotypes in physiological response to sequential soil drying and rewetting

Abstract

Soybean genotypes show diverse physiological responses to drought, but specific physiological traits that can be used to evaluate drought tolerance have not been identified. In the present study we investigated physiological traits of soybean genotypes under progressive soil drying and rewetting, using a treatment mimicking field conditions. After a preliminary study with eight soybean genotypes, two drought-tolerant genotypes and one susceptible genotype were grown in the greenhouse and subjected to water restriction. Leaf expansion rate, gas exchange, water relation parameters, total chlorophyll (Chl), proline contents of leaves, and root xylem pH were monitored in a time course, and plant growth and root traits were measured at the end of the stress cycle. Drought-tolerant genotypes maintained higher leaf expansion rate, net photosynthetic rate (P n ), Chl content, instantaneous water use efficiency (WUEi), % relative water content (RWC), water potential (ψ w ), and turgor potential (ψ p ) during progressive soil drying and subsequent rewetting than the susceptible genotypes. By contrast, stomatal conductance (g s ) and transpiration rate (T r ) of tolerant genotypes declined faster owing to dehydration and recovered more sharply after rehydration than the same parameters in susceptible ones. Water stress caused a significant increase in leaf proline level and root xylem sap pH of both genotypes but tolerant genotypes recovered to pre-stress levels more quickly after rehydration. Tolerant genotypes also produced longer roots with higher dry mass than susceptible genotypes. We conclude that rapid perception and adjustment in response to soil drying and rewetting as well as the maintenance of relatively high P n , %RWC, and root growth constitute the mechanisms by which drought-tolerant soybean genotypes cope with water stress.

Physiological responses of Urochloa ruziziensis inoculated with Azospirillum brasilense to severe drought and rehydration conditions

“…4a and 4b). This fact was also registered in soybean crops (Hossain et al, 2014), which represents resistence of plant to water deficit. The WUE and iWUE were also used to differentiate cultivars of Cynodon spp.…”

Relative leaf expansion rate and other leaf-related indicators for detection of drought stress in chili pepper (Capsicum annuum L.).

“…LA data are required for many significant and frequently used parameters in growth analysis, i.e. specific leaf weight (SLW), net assimilation rate (NAR), and specific leaf area (SLA) (Hossain et al, 2014;Guendouz et al, 2016), in addition to RLER, SLFW, SLWC, and TLA. Even though SLW in plant growth analysis is mostly calculated based on dry weight, it can also be calculated based on fresh weight (SLFW) or at maximum leaf turgidity level.…”

Calibration, uncertainties and use of soybean crop simulation models for evaluating strategies to mitigate the effects of climate change in Southern Brazil

“…For AQUACROP, it was defined during calibration a maximum root depth of 110 cm, resulting in maximum water available of 150 mm (Figure 9d). For FAO (Figure 9e), there is two maximum depth, of 60 cm to rainfed condition, and 50 cm to irrigated, because we assume that under rainfed conditions the roots increased on depth (HOSSAIN et al, 2014), where water available reach maximum values close of 100 mm. Figure 9 not means that all water is available to water uptake, because DSSAT, APSIM and MONICA consider water uptake a function of root density in each soil layer, while AQUACROP and FAO use an index to limit water uptake due to reduction of water in the soil.…”

“…However, the speed of recovery from water deficit is another drought tolerance trait that should be investigated (BRODRIBB, 1996;HOSSAIN et al, 2014).…”