中文摘要：

在大田条件下,以新陆早13号和新陆早33号为材料,研究水分亏缺与足水处理下不同基因型棉花生育后期叶片光合特性、水分利用效率变化与叶片早衰的关系。结果表明：花后不同水分胁迫对棉花主茎叶光合速率（Pn）、气孔导度（Gs）、蒸腾速率（Tr）、水分利用效率（WUE）及干物质积累与分配均有显著影响。水分亏缺下2个品种生育后期叶片Pn、Gs、Tr均明显下降,WUE也低于对照,但新陆早33号的WUE高于新陆早13号。足水处理下新陆早13号叶片Pn、Gs和WUE显著降低,Tr明显增加;新陆早33号后期叶片Pn、Gs和WUE变化不明显,Tr增加,使得新陆早33号棉株干物质积累维持较稳定水平。这说明新陆早33号叶片具有较弱的蒸腾作用,较强的水分利用效率,使其对外界水分亏缺以及足水处理适应性较强,且后期叶片光合功能维持时间长,干物质积累较多,从而使其叶片衰老较新陆早13号缓慢;而新陆早13号叶片对逆境适应性较差和光合机构破坏较严重是促进其早衰的原因。

英文摘要：

Under field condition,this experiment took Xinluzaol3 and Xinluzao33 for the materials to study the changes of leaf photosynthetic characteristics,water use efficiency（WUE） and senescence of the different genotypes during the late development of cotton under different water treatments.The results show that,after anthesis,water stress affects significantly photosynthetic rate（Pn）,stomatal conductance（Gs）.transpiration rate（Tr）,water use efficiency（WUE） as well as dry matter accumulation and allocation of leaves on the cotton main stem.Under water deficiency condition,Pn.G.s and Tr in the leaves of the two varieties decrease obviously and water use efficiency（WUE） is lower than the control,with WUE of Xinluzao33 higher than Xinluzao13.Under the condition of sufficient water,Pn,Gs and WUE of Xinluzao13 leaves are significantly lower than the control, and Tr increases significantly;Pn,Gs and WUE in the leaves of Xinluzao33 remain almost the same except for the increase of Tr,which makes dry material accumulation of Xinluzao33 maintain at a relatively stable level.Xinluzao33 leaves have weaker transpiration and stronger water use efficiency than Xinluzaol3,which endows it with stronger adaptability to water stress and a longer-lasting photosynthetic function and more dry matter accumulation at the late stage.All these lead to a slower rate of leaf senescence than Xinluzaof 3.The relatively poor adaptability and more serious damage of the photosynthetic apparatus of Xinluzao13 leaves are the main reasons of leaf senescence.