摘要：Persistent drought severely inhibits plant growth and productivity, which negatively affects terrestrial primary productivity worldwide. Therefore, it is important to investigate the impacts of drought on plant leaf CO 2 /H 2 O exchange and water use efficiency. This study assessed the responses of net photosynthesis ( Pn ), stomatal conductance ( Gs ), transpiration ( Tr ), and instantaneous water use efficiency (WUE) to drought based on a worldwide meta-analysis of 112 published studies. The results demonstrated that drought decreased Pn , Tr , and Gs significantly and differently among different moderators. C 4 plants had smaller Pn reduction than C 3 plants, which gives C 4 plants an advantage in Pn . But their WUE decreased under drought conditions, indicating a great flexibility in C 4 WUE. Annual herbs sacrificed WUE (−6.2%) to maintain efficient Pn . Perennial herbs took a different strategy in response to drought with an increased WUE (25.1%). Deciduous tree species displayed a greater increase in WUE than conifers and evergreen species. Additionally, Gs had a significant correlation with Pn and Tr , but an insignificant correlation with WUE, which could be because WUE is affected by other factors (e.g., air flow, CO 2 concentration, and relative humidity). These findings have significant implications for understanding the worldwide effects of drought on plant leaf CO 2 /H 2 O exchange and water use efficiency.
关键词：drought stress; meta-analysis; leaf CO 2 /H 2 O exchange; water sue efficiency
