短期干旱对水稻叶水势、光合作用及干物质分配的影响

采用盆栽水分试验，研究了不同生育期短期干旱处理对水稻叶水势、光合作用和干物质分配的影响．结果表明，干旱胁迫后，水稻叶水势低于对照，午后叶水势回升缓慢。凌晨叶水势随土壤含水量的降低而降低，表现为阈值反应。叶片净光合速率与凌晨叶水势密切相关，低于凌晨叶水势临界值，水稻叶片净光合速率急剧下降在水稻抽穗期和灌浆期叶片净光合速率显著下降的凌晨叶水势临界值为-1.04和-1．13MPa，对应的土壤含水量阈值分别为饱和含水量的61.0％和50．9％，土壤水势分别为-0．133和-0．240MPa干旱胁迫下单叶净光合速率的日变化规律表现为：胁迫较轻时，单叶净光合速率在正午附近出现低谷；胁迫严重时，净光合速率全天低于对照，且不及对照的一半。短期干旱后，水稻叶、根、穗的分配指数均降低，茎鞘的分配指数升高。本研究可为水稻节水灌溉管理和水分限制下水稻的生长模拟提供生理基础和理论依据。

Effect of short-term drought on leaf water potential,photosynthesis and dry matter partitioning in paddy rice

Pot experiments were conducted to study the effect of short-term drought at four rice growth stages on leaf water potential, photosynthesis and dry matter partitioning in paddy rice. The leaf water potential of rice plant under water stress was lower than that of CK, and the difference increased after midday.The predawn leaf water potential of rice plant decreased significantly when soil water content or soil water potential went down a threshold value, resulted in an obvious decline in the single leaf net photosynthetic rate. In compared with the well-watered treatment, the net photosynthetic rate under severe water stress decreased by more than 50%. The partitioning indexes of leaf, root and spike decreased, while that of stem and sheath increased after short-term drought.