中文摘要：

于2005—2006年在南京农业大学卫岗试验站进行盆栽试验,研究花铃期土壤干旱及复水后棉花光合与蒸腾特性及水分利用率对氮素的响应.结果表明：与正常灌水处理（CK）相比,干旱处理棉花随土壤相对含水量（SRWC）的减少,其净光合速率（Pn）和蒸腾速率（Tr）迅速降低;在干旱处理前期,由于棉花Tr下降幅度高于Pn,水分利用率（WUE）表现为上升趋势,而后随SRWC和Pn的降低,WUE呈逐渐下降趋势.土壤干旱改变了Pn和Tr的日变化趋势,干旱处理棉花Pn和Tr从8：00到16：00一直呈下降趋势,而CK则呈单峰曲线,Pn和Tr峰值分别出现在10：00—11：00和12：00;干旱处理和CK的WUE日变化均呈先降后升的趋势,谷值出现在12：00.干旱条件下棉花的Pn和Tr随氮素水平的提高而降低,而WUE则表现为相反趋势;复水后,干旱处理棉花Pn、Tr及WUE日变化趋势与CK一致,但其值低于CK,该趋势在施氮肥条件下表现尤为明显.可见,棉花花铃期土壤干旱条件下增施氮肥虽然有利于WUE的提高,但却降低了棉花的光合性能.

英文摘要：

With pot culture,the physiological responses of cotton plant to fertilizer nitrogen at flowering and boll-forming stages were studied under soil drought and after re-watering.The results showed that under soil drought,the net photosynthetic rate（Pn）and transpiration rate（Tr）declined rapidly with decreasing soil relative water content（SRWC）.At the early stage of soil drought,owing to the declining degree of Tr was greater than that of Pn,the WUE had an increasing trend;but after then,the WUE decreased with declining SRWC and Pn.Soil drought altered the diurnal patters of Pn and Tr,i.e.,decreased continuously from 8：00 to 16：00,while in CK,their peak values appeared at 10：00-11：00 and 12：00,respectively.The diurnal patterns of WUE in drought treatment and CK were the same,i.e.,decreased first and increased then,with the bottom appeared at 12：00.Under soil drought,the Pn and Tr decreased with increasing fertilizer nitrogen level,while WUE was in adverse.After re-watering,the diurnal patterns of Pn,Tr and WUE were similar to CK,but their values were smaller than CK,especially under nitrogen application.It was suggested that under soil drought,nitrogen fertilization could be helpful to the increase of water use efficiency,but decreased the photosynthesis of cotton plant at its flowering and boll-forming stages.