Abstract
The influence of 24-epibrassinolide (EBR24), applied to leaves at a concentration of 5 μM, on plant physio-biochemistry and its reflection on crop water productivity (CWP) and other agronomic traits of six maize hybrids was field-evaluated under semi-arid conditions. Two levels of irrigation water deficiency (IWD) (moderate and severe droughts; 6000 and 3000 m3 water ha−1, respectively) were applied versus a control (well-watering; 9000 m3 water ha−1). IWD reduced the relative water content, membrane stability index, photosynthetic efficiency, stomatal conductance, and rates of transpiration and net photosynthesis. Conversely, antioxidant enzyme activities and osmolyte contents were significantly increased as a result of the increased malondialdehyde content and electrolyte leakage compared to the control. These negative influences of IWD led to a reduction in CWP and grain yield-related traits. However, EBR24 detoxified the IWD stress effects and enhanced all the above-mentioned parameters. The evaluated hybrids varied in drought tolerance; Giza-168 was the best under moderate drought, while Fine-276 was the best under severe drought. Under IWD, certain physiological traits exhibited a highly positive association with yield and yield-contributing traits or CWP. Thus, exogenously using EBR24 for these hybrids could be an effective approach to improve plant and water productivity under reduced available water in semi-arid environments.
Highlights
Irrigation water deficiency (IWD) is a substantial abiotic stress factor negatively affecting the growth and productivity of different crops
The adverse effects of severe drought stress (SDS) exceeded those of Moderate drought stress (MDS) and decreased the total chlorophyll, carotenoids, photochemical activity, and photosynthetic efficiency by 49.1%, 54.0%, 32.6%, and 25.5% in the same order compared with the WW plants
The results indicated that EBR24 enhanced the drought tolerance in maize hybrids by improving the chlorophyll and carotenoids contents, photochemical activity, and photosynthetic efficiency in the tested hybrids, especially under
Summary
Irrigation water deficiency (IWD) is a substantial abiotic stress factor negatively affecting the growth and productivity of different crops. It is linked to the reduction of arable land and food production [1], as well as livestock raising around the world. It causes changes in the indices of plant morphology, physio-biochemistry, including the antioxidant defense system, and molecular biology of plants [2,3,4,5,6,7]. IWD by avoiding dehydration by retaining a higher amount of water through many plant strategies (e.g., reduced leaf area, stomatal closure, and older leaf senescence), so it rarely corresponds to high yield, and/or by tolerating dehydration by functioning under the IWD event [11,12]. An innate inconsistency between the accumulation of biomass and avoidance of stress has been demonstrated, because the low transpiration rates affect the acquisition of photo-assimilate that depends on the stomatal aperture and leaf area [12,13]
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