Physio‐morphological, biochemical, and anatomical traits of drought‐tolerant and susceptible sorghum cultivars under pre‐ and post‐anthesis drought

Abstract

Understanding the physiological mechanisms that control drought tolerance in crop plants is vital for effective breeding. In this study, we characterized drought stress responses in four sorghum cultivars exhibiting differential levels of drought tolerance at pre-and post-anthesis. Greenhouse-grown plants were subjected to two types of drought treatment, water stress (WS) and desiccant-induced water stress (DA), timed to occur at pre-and post-anthesis. Multiple physiological measurements were then made revealing varying responses among the experimental cultivars. The pre-and postflowering drought-tolerant cultivar P898012 showed a significantly higher net photosynthetic rate, higher transpiration rate, and greater stomatal conductance compared to the drought-susceptible cultivars at both pre-and post-anthesis. A significantly greater stomatal size was also detected in P898012, while the highest stomatal density was found in the drought-susceptible cultivar P721Q. Meanwhile, the two post-flowering drought-tolerant cultivars P898082 and B35 had a higher starch content and exhibited greater osmotic potential under post-anthesis water stress. Compared to WS and wellwatered control plants, a greater increase in root biomass was observed in P898012 under DA at pre-anthesis. This finding suggests that plants invested more assimilates into the roots under severe DA at pre-anthesis. Overall, our results show good conformity between drought tolerance in sorghum and key physiological mechanisms of stomatal conductance, root growth patterns, and starch accumulation, all of which act as coping mechanisms during critical drought-sensitive growth stages. | INTRODUCTIONDrought is one of the key abiotic stresses limiting crop productivity worldwide (Cha-um et al., 2012), affecting plant productivity by inducing stomatal closure, and thereby reducing photosynthesis (Németh et al., 2002) and growth (Bibi et al., 2012). With growing effects of climate change, the development of drought-tolerant and climateresilient crops is essential for survival under unfavorable environmental conditions and maintenance of high yield. Plants respond to water stress via a series of cellular events involving physiological, morphological and biochemical processes. Under water stress, photosynthesis decreases, osmotic potential is reduced, and consequently, the availability of photosynthetic assimilates and energy becomes limited. During pre-anthesis assimilation, the necessary resources for grain filling temporarily accumulate within the stem as non-structural carbohydrates such as starch, sucrose, monosaccharides, isoprenoids, and fructans (Schnyder, 1993;Jensen and Wilkerson, 2017). It has been suggested that genotypes that can synthesize and store large amounts of starch could potentially exhibit improved grain yield by mobilizing these reserves to the grains when photosynthesis is inhibited

Identification of Sorghum (Sorghum bicolor (L.) Moench) Genotypes with Potential for Hydric and Heat Stress Tolerance in Northeastern Mexico

“…Although sorghum is a crop adapted to dry climates, hydric stress is considered the most important abiotic limiting factor for growth and productivity [9][10][11][12]. This negative effect can be mitigated through genetic improvement, taking advantage of the genetic variability of the species through tolerant germplasm evaluation and selection [13][14][15]. To achieve such goal, is important to understand the physiological responses caused by drought and high temperatures [1,10,16,17].…”

“…The cell membrane stability and the relative water content (RWC) in leaves are physiological selection indices in plants when selecting for tolerance to hydric stress or high temperatures [18][19][20][21][22][23]. Hydric stress affects the water metabolism in plants, as it limits nutrient absorption [24][25][26], transpiration rates, and plant growth [4,27,28] and interferes with physiological and biochemical processes which diminishes yield and crop quality [15,29]. Additionally, hydric stress drastically diminishes growth parameters such as biomass accumulation, root to shoot ratio, foliar area, and chlorophyll concentration [30][31][32][33].…”

Salt and Water Stress Responses in Plants

“…This has been demonstrated through various test regarding physio-morphological and biochemical traits including desiccation survival, heat tolerance, osmolytes, ion homeostasis etc. [110][111][112][113][114][115].…”

Azospirillum Brasilense Innoculation Combined With Different Levels of Nitrogen Fertilization and Its Effects in the Grain Sorghum Subjected to Water Restriction

“…Understanding plant physiological responses to drought is a key aspect for agriculture in the current scenarios, since one of the most urgent problems of the present time are the combined effects and impacts of climate changes in the different biomes (Akman;Zhang;Ejeta, 2020). The imbalance triggered by adverse meteorological conditions such as alterations in the temperature patterns, humidity and precipitation are capable of promoting significant alterations in the water availability of a given region, an element that is key to agriculture (Moncada;Petersen;Munkholm, 2021).…”

“…Sorghum yields are capable of facing those climate adversities due to its high drought tolerance (Akman;Zhang;Ejeta, 2020). Sorghum (Sorghum bicolor L. Moench) is a grass native from Africa, and belongs to the Andropogeneae tribe.…”