Drought response at early seedling stage of pearl millet

The study evaluates the impact of drought at an early seedling stage of pearl millet. Drought stress imposed for 7, 14 and 21d showed considerable changes in morpho-physiological attributes and inhibited root and shoot growth. After 14 and 21d of stress, there was a significant decline in total chlorophyll content with visible chlorosis lesions in leaves. This was followed by significant decline in biomass and relative water content after 7, 14 and 21d of stress. Drought stress raised the levels of ROS such as H2O2 and O2⸺ in root and shoot to a significant level along with increased rate of lipid peroxidation. In roots, the uptake of Evans blue dye indicated severe loss of plasma membrane integrity as a consequence of high ROS induced peroxidation of membrane lipids. With high ROS production, both enzymatic and non-enzymatic antioxidants are degraded. The activities of antioxidant enzymes such as CAT, GPx, GR and SOD under drought were significantly inhibited in root and shoot as compared to their controls. Similarly, non-enzymatic antioxidant such as AsA and GSH were significantly lowered under drought stress. Our results clearly revealed that pearl millet is highly susceptible to drought condition at an early seedling stage.本研究评估了干旱对珍珠粟幼苗早期阶段的影响。施加7、14和21天的干旱胁迫会使植株的形态生理特性发生显著变化，并抑制根系与地上部的生长。胁迫14天和21天后，叶片总叶绿素含量显著下降，并出现可见的褪绿病斑；在此基础上，胁迫7、14和21天后，植株生物量与相对含水量均出现显著下降。干旱胁迫会使根系与地上部的活性氧（Reactive Oxygen Species, ROS）水平，如过氧化氢（H₂O₂）与超氧阴离子（O₂⁻），显著升高，同时脂质过氧化速率加快。在根系中，伊文思蓝（Evans Blue）染料的摄取量表明，由于高活性氧诱导的膜脂过氧化，质膜完整性遭到严重破坏。随着活性氧大量产生，酶促与非酶促抗氧化系统均发生降解。与对照组相比，干旱胁迫下根系与地上部的抗氧化酶类，如过氧化氢酶（Catalase, CAT）、谷胱甘肽过氧化物酶（Glutathione Peroxidase, GPx）、谷胱甘肽还原酶（Glutathione Reductase, GR）与超氧化物歧化酶（Superoxide Dismutase, SOD）的活性均受到显著抑制。同样，干旱胁迫下非酶促抗氧化物质，如抗坏血酸（Ascorbic Acid, AsA）与谷胱甘肽（Glutathione, GSH）的含量也显著降低。本研究结果明确表明，珍珠粟在幼苗早期阶段对干旱环境具有高度敏感性。