中文摘要：

于2005—2006年在江苏南京农业大学卫岗试验站进行盆栽试验，设置正常灌水（土壤含水量为田间持水量的75%左右）和棉花花铃期土壤短期渍水处理（将正常灌水的棉花增加灌水至盆内有可见明水，持续8 d，然后用导管排除表面水层，使盆内土壤含水量逐渐恢复到田间持水量的75%左右），每个水分处理设置3个氮素水平（0、3.73、7.46 g N pot^-1，分别相当于大田0、240、480 kg N hm^-2），研究氮素对花铃期短期渍水棉花根系生长的影响。结果表明，在渍水处理结束时，与正常灌水处理相比，根干重和根冠比（R∶S）均降低；根系可溶性蛋白含量、超氧化物歧化酶（SOD）和过氧化氢酶（CAT）活性降低，过氧化物酶（POD）活性升高，丙二醛（MDA）含量升高；棉花根系活力和单株光合速率（CAP）显著降低。增加施氮可降低渍水棉花根系SOD活性，提高POD和CAT活性，以3.73 g N pot^-1（240 kg N hm^-2）施氮水平下的棉花根干物重最大，根系MDA含量最低，根系活力最强，单株光合速率（CAP）最高，相应籽棉产量最高。渍水停止15 d后，渍水棉花根系抗氧化酶活性和MDA含量与正常灌水处理的差异较小；施氮仍可提高棉花根系POD与CAT活性，降低MDA含量，增强根系活力，提高CAP。

英文摘要：

The flowering and boll development stage is the key period for cotton quality and yield. Waterlogging during this period significantly inhibits cotton development and reduces final yield. Nitrogen fertilizer is considered to be an effective up-regulatory element for crop growth. The objective of this investigation was to evaluate effects of nitrogen on cotton resistance to soil waterlogging in terms of the changes of root dry matter accumulation, antioxidant enzyme activities and root vigor under short-term waterlogging. A pot experiment wasconducted with three N levels （0, 3.73, and 7.46 g N pot^-1 equivalent to 0, 240, and 480 kg N ha^-1, respectively）, waterlogging for eight days and then recovering for fifteen days. The results showed that the root dry matter weight and the Root/Shoot ratio of plants by waterlogged decreased, and the root dry matter weight reached a peak at the 240 kg N ha^-1 under waterlogging, but the root/shoot ratio decreased with the increase of N application. Under waterlogging, soluble protein content significantly decreased in comparison with well-watered cotton, and the reduced degree increased with increasing N application. Malondialdehyde （MDA） content in cotton roots was significantly （P 〈0.05） increased, with the lowest at the 240 kg N ha^-1 during waterlogging. Application of N increased the activities of peroxidase （POD） and catalase （CAT） of cotton roots, but decreased superoxide dismutase （SOD） activity during waterlogging. Both root vigor and CAP decreased by waterlogging, were the highest at the 240 kg N ha^-1. At the 15 d after terminating waterlogging, N application promoted root vigor and CAP, but decreased MDA content. These results suggest that appropriate N supply （240 kg N ha^-1 in this investigation） may contribute to waterlogging resistance of cotton plants through adjusting the antioxidant enzyme activities of roots, decreasing lipid peroxidation and enhancing root vigor during waterlogging （waterlogging for eight days in this inves