Abstract：
Potassium (K) deficiency occurs commonly in crop plants. Optimal K nutrition is particularly important when plants are exposed to stress conditions (especially drought and heat) because a cellular demand for K increases. Low K in plant tissues is known to aggravate the effects of drought stress by impairing the osmoregulation process and the photosynthetic carbon metabolism. However, despite numerous publications about the role of K in enhancing tolerance to drought stress in crop plants, our understanding of the major mechanisms underlying the stress-mitigating effects of K is still limited. This paper summarizes and appraises the current knowledge on the major protective effects of K under drought stress, and then proposes a new K-related drought stress-mitigating mechanism, whereby optimal K nutrition may promote partitioning of carbohydrates in stem tissues and subsequent mobilization of these carbohydrates into developing grain under drought stress. The importance of stem reserves of carbohydrates is based on limited photosynthetic capacity during the grain-filling period under drought conditions due to premature leaf senescence as well as due to impaired assimilate transport from leaves to the developing grains. Plants with a high capacity to store large amounts of soluble carbohydrates in stems before anthesis and mobilize them into grain post-anthesis have a high potential to yield well in dry and hot environments. In practice, particular attention needs to be paid to the K nutritional status of plants grown with limited water supply, especially during grain filling. Because K is the mineral nutrient deposited mainly in stem, a special consideration should be given to stems of crop plants in research dealing with the effects of K on yield formation and stress mitigation.
摘要：
钾(K)缺乏通常发生在作物植物中。当植物暴露于胁迫条件（尤其是干旱和高温）时，最佳的钾营养尤其重要，因为细胞对钾的需求增加。已知植物组织中的低钾通过损害渗透调节过程和光合碳代谢来加剧干旱胁迫的影响。然而,尽管有许多关于钾在增强作物对干旱胁迫的耐受性中的作用的出版物，我们对K缓解压力的主要机制的理解仍然有限.本文总结和评价了当前关于干旱胁迫下钾的主要保护作用的知识，然后提出了一种新的与钾相关的干旱缓解机制，因此，最佳的钾营养可以促进茎组织中碳水化合物的分配，并随后在干旱胁迫下将这些碳水化合物动员到发育中的谷物中。碳水化合物的茎储备的重要性基于干旱条件下谷物灌浆期间有限的光合能力，这是由于叶片过早衰老以及由于从叶片到发育中的谷物的同化物运输受损。具有在花前将大量可溶性碳水化合物储存在茎中并在花后将它们动员到谷物中的高容量的植物在干燥和热环境中具有很高的产量潜力。在实践中,需要特别注意供水有限的植物的钾营养状况，尤其是在谷物灌浆期间。因为K是主要沉积在茎中的矿物质，在研究钾对产量形成和缓解胁迫的影响时，应特别考虑农作物的茎。
