中文摘要：

于2005年在江苏南京（长江流域下游棉区）和徐州（黄河流域黄淮棉区）棉田设置不同氮素水平（零氮：0kgN·hm^-2，适氮：240kgN·hm^-2，高氮：480kgN·hm^-2）试验，研究氮素对不同开花期棉铃（伏前桃、伏桃和秋桃）纤维比强度形成生理基础的影响．结果表明：与适氮处理相比，零氮处理显著降低了棉铃对位叶氮浓度，增加了C／N，影响程度随开花期的推迟而加大，导致伏桃、秋桃对位叶制造和运输光合产物的能力在棉铃发育中后期大幅度下降，棉纤维的相对生长速率以及纤维发育关键酶蔗糖合成酶和β-1，3-葡聚糖酶活性降低，纤维素快速累积持续期缩短，纤维比强度显著降低；高氮处理显著增加了棉铃对位叶氮浓度，降低了C／N，影响程度随开花期的推迟而降低，其降低了伏前桃、伏桃发育过程中光合产物向纤维分配的比例、棉铃发育前中期的纤维发育关键酶活性及纤维素累积速率，导致其纤维比强度亦显著降低．综合分析认为，适宜的施氮量可以协调棉花的“源库”关系，有利于促进不同开花期棉铃高纤维比强度的形成．与适氮处理相比，零氮处理的伏前桃、伏桃和秋桃纤维比强度分别降低了1．8％、5．8％和13．0％，高氮处理则分别降低了8．2％、7．4％和-2．4％．

英文摘要：

Abstract： To study the roles of nitrogen fertilization in regulating the physiological bases of fiber specific strength formation in cotton bolls bloomed at different dates （July 15, July 25, and September 10; expressed as PSB, SB, and AB, respectively）, field experiments were conducted in two sites with different ecological conditions, i. e. , Nanjing （ middle lower reach of Yangtze River Valley） and Xuzhou （Yellow River Valley）. Three treatments （0, 240, and 480 kg N · hm^-2） were installed. The results showed that comparing with applying optimum nitrouen （240 ku N · hm^-2）,no N application decreased the N content and increased the C/N in the leaves subtending cotton bolls significantly, and the effects increased with postponing blooming date, which, to a great extent, led to the decreases of the capabilities of the leaves subtending cotton bolls bloomed at SB and AB in the accumulation and transportation of photosynthetic products, the relative growth rate of fiber in cotton bolls, and the activities of key enzymes （ sucrose synthetase and 15-1,3-glucanase） during the middle-later period of fiber development, and also, the decline of cellulose speedily ac- cumulating duration in cotton fiber and of the fiber specific strength in the bolls bloomed at SB and AB. On the contrary, applying high nitrogen （480 kg N · hm^-2） increased the N content but decreased the C/N in the leaves subtending cotton bolls significantly, and the effects decreased with postponing blooming date, whieh deereased the distribution proportion of photosynthetic produets to fiber, the key enzyme activities during the early-middle period of fiber development, and the momentary rate of eellulose accumulation in the fiber of the bolls blooming at PSB and SB, resulting in a significant decrease of the fiber specific strength. It was suggested that appropriate N application could regulate the ＇ source-sink＇ relation of cotton, and benefit the high fiber specific strength formation in cotton bolls bloomed at d