Scarcity of water is a severe environmental constraint to plant productivity. Drought-induced loss in crop yield probably exceeds losses from all other causes, since both the severity and duration of the stress are critical. Here, we have reviewed the effects of drought stress on the growth, phenology, water and nutrient relations, photosynthesis, assimilate partitioning, and respiration in plants. This article also describes the mechanism of drought resistance in plants on a morphological, physiological and molecular basis. Various management strategies have been proposed to cope with drought stress. Drought stress reduces leaf size, stem extension and root proliferation, disturbs plant water relations and reduces water-use efficiency. Plants display a variety of physiological and biochemical responses at cellular and whole-organism levels towards prevailing drought stress, thus making it a complex phenomenon. CO₂ assimilation by leaves is reduced mainly by stomatal closure, membrane damage and disturbed activity of various enzymes, especially those of CO₂ fixation and adenosine triphosphate synthesis. Enhanced metabolite flux through the photorespiratory pathway increases the oxidative load on the tissues as both processes generate reactive oxygen species. Injury caused by reactive oxygen species to biological macromolecules under drought stress is among the major deterrents to growth. Plants display a range of mechanisms to withstand drought stress. The major mechanisms include curtailed water loss by increased diffusive resistance, enhanced water uptake with prolific and deep root systems and its efficient use, and smaller and succulent leaves to reduce the transpirational loss. Among the nutrients, potassium ions help in osmotic adjustment; silicon increases root endodermal silicification and improves the cell water balance. Low-molecular-weight osmolytes, including glycinebetaine, proline and other amino acids, organic acids, and polyols, are crucial to sustain cellular functions under drought. Plant growth substances such as salicylic acid, auxins, gibberrellins, cytokinin and abscisic acid modulate the plant responses towards drought. Polyamines, citrulline and several enzymes act as antioxidants and reduce the adverse effects of water deficit. At molecular levels several drought-responsive genes and transcription factors have been identified, such as the dehydration-responsive element-binding gene, aquaporin, late embryogenesis abundant proteins and dehydrins. Plant drought tolerance can be managed by adopting strategies such as mass screening and breeding, marker-assisted selection and exogenous application of hormones and osmoprotectants to seed or growing plants, as well as engineering for drought resistance.

中文翻译：

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植物干旱胁迫：影响，机制和管理

缺水是严重影响植物生产力的环境因素。由于干旱的严重程度和持续时间都是至关重要的，干旱导致的作物单产损失可能超过其他所有原因的损失。在这里，我们综述了干旱胁迫对植物生长，物候，水和养分关系，光合作用，同化物分配和呼吸作用的影响。本文还从形态，生理和分子的角度描述了植物的抗旱机理。已经提出了各种管理策略来应对干旱压力。干旱胁迫会减少叶片大小，茎伸长和根系增殖，扰乱植物水分关系并降低水分利用效率。植物在细胞和整个生物体水平上对普遍的干旱胁迫表现出多种生理和生化反应，因此使其成为一种复杂的现象。一氧化碳₂叶片的同化作用主要是由于气孔关闭，膜损伤和各种酶（特别是CO _2的酶）活性降低而减少固定和三磷酸腺苷的合成。通过光呼吸途径的代谢物通量增加，因为这两个过程均产生活性氧，从而增加了组织的氧化负荷。在干旱胁迫下，活性氧对生物大分子造成的伤害是阻碍生长的主要因素之一。植物表现出一系列抵抗干旱胁迫的机制。其主要机理包括通过增加抗扩散能力来减少水分流失，通过多根和深根系统提高水分吸收量以及有效利用水分，以及通过减少叶片的多汁性来减少蒸腾作用。在营养物中，钾离子有助于渗透调节。硅增加根部内胚层硅化作用并改善细胞水平衡。低分子量渗透物，包括甘氨酸甜菜碱，脯氨酸和其他氨基酸，有机酸和多元醇对干旱条件下维持细胞功能至关重要。水杨酸，植物生长素，赤霉素，细胞分裂素和脱落酸等植物生长物质可调节植物对干旱的反应。多胺，瓜氨酸和几种酶可作为抗氧化剂，减少缺水的不利影响。在分子水平上，已经鉴定了几种干旱响应基因和转录因子，例如脱水响应元件结合基因，水通道蛋白，胚胎后期晚期丰富蛋白和脱水蛋白。植物的耐旱性可以通过采取策略来进行管理，例如大规模筛选和育种，标记辅助选择以及激素和渗透保护剂在种子或生长中植物的外源应用以及抗旱工程。