中文摘要：

2005～2006年在南京农业大学卫岗试验站进行盆栽试验,设置正常灌水和棉花花铃期土壤短期干旱处理,每个处理再设置3个氮素水平（N 0、240、480 kg/hm^2）,研究氮素对花铃期短期干旱再复水后棉花纤维比强度形成的影响。结果表明,干旱处理结束时,干旱处理棉花的纤维可溶性蛋白含量较正常灌水处理显著降低,而内源保护酶,即：超氧化物歧化酶（SOD）、过氧化氢酶（CAT）和过氧化物酶（POD）活性升高,丙二醛（MDA）含量增加;纤维加厚发育相关酶,即：蔗糖合成酶、磷酸蔗糖合成酶、β-1,3-葡聚糖酶和IAA氧化酶的活性均显著降低。在复水后第10 d,干旱处理棉花的纤维内源保护酶活性迅速恢复到正常灌水处理水平,MDA含量降低,但纤维发育相关酶的活性仍低于相应正常灌水处理,纤维比强度亦显著低于正常灌水处理。在棉花的纤维加厚发育期土壤短期干旱再复水条件下,以N 240 kg/hm^2最有利于形成高强纤维。干旱期间该处理棉花的纤维内源保护酶活性高,细胞膜脂过氧化程度最低,其纤维加厚发育相关酶活性均最高;复水后该处理的纤维内源保护酶活性迅速恢复,MDA含量最低,棉花的纤维加厚发育相关酶活性仍处于最高值,有利于纤维素的合成与累积,最终纤维比强度亦最大。施氮不足（N 0 kg/hm^2）或过量施氮（N 480 kg/hm^2）均表现出相反的趋势。

英文摘要：

Pot experiments were conducted to study the effects of nitrogen on the cotton fiber strength formation under water stress and after re-watering during the flowering and boll-forming stage in Nanjing Agricultural University in 2005 and 2006. Within each water treatment, three nitrogen levels were imposed： N 0, 240 and 480 kg/ha. The results showed that water stress significantly reduced soluble protein content in cotton fiber, increased the antioxidant enzyme activities of SOD, CAT and POD and MDA content at the end of soil water stress, but reduced the fiber thickening key enzyme activities of sucrose synthetase, β-1,3-glucanase, sucrose phosphate synthetase, and IAA oxidase. On the 10th day after rewatering, there was no significant difference of SOD, CAT and POD activity between water-stressed and well-watered cotton. However, MDA content declined, and the fiber thickening related key enzyme activities were still lower than wellwatered treatments. The fiber strength was also reduced. The resuh of 2-year experiment showed that N 240 kg/ha was the optimal nitrogen application rate for forming high-strength fibre under soil water stress and afterward re-watering because the antioxidant enzyme activities and the fiber thickening key enzyme activities were highest, and MDA content were the lowest, thus leading to the greatest fibre strength. In this experiments, deficient （N 0 kg/ha） and excessive （N 480 kg/ha） nitrogen supply are of disadvantaged to the fiber thickening key enzyme activities and cotton fibre strength.