氮肥对新疆棉花产量形成期叶片光合特性的调节效应

在新疆生态条件下,采用裂区设计研究了氮肥用量对棉花产量形成期叶片光合特性的调节效应。结果表明,适量追施氮肥在一定程度上可以改善叶片光合性能,提高植株生育后期叶片叶绿素含量和硝酸还原酶(NR)活性;维持叶片较高的PSⅡ潜在活性(Fv/Fo)和PSⅡ光化学最大效率(Fv/Fm);提高中下部叶片的光合速率,延缓了叶片衰老,保证了棉花生育后期光合产物的形成,从而使棉花达到高产。这种调节效应因品种和生育时期的不同而异。新陆早6号在盛铃前期叶片叶绿素含量、NR活性、光合速率及Fv/Fo和Fv/Fm随氮肥用量增加而增加,盛铃后期至吐絮期叶绿素含量、Fv/Fo和Fv/Fm、叶片光合速率等指标均以中氮处理(300.kg/hm2)最高,高氮处理易造成植株盛花期生长过旺,群体荫蔽,影响了叶片光合作用;新陆早7号中氮处理与高氮处理之间差异不明显。因此,生产上应根据不同品种和生育时期进行合理施肥,避免因施肥不当造成产量下降和浪费肥料。

Effects of nitrogen rates on photosynthetic characteristics and yield of high-yielding cotton in Xinjiang

The effects of nitrogen rates on photosynthetic characteristics and yield of high-yielding cotton in Xinjiang were investigated with two cotton varieties, Xinluzao 6 and Xinluzao 7. The result showed that proper nitrogen rate (N 300kg/hm²) could improve photosynthetic characteristics of cotton, the chlorophyll content, nitrate reductase (NR) activity and net photosynthesis rate (Pn) of the middle and bottom leaf raised at later growth stages. The activity of PSⅡ (F_v/F_o), maximum photochemical efficiency of PSⅡ (F_v/F_m) were maintained at a relatively high level. Therefore, the physiological activity in middle and bottom leaves of cotton was raised,and senescence of leaf delayed, photosynthetic product was sufficiency during the later growth stages, finally it could lead to increase of yields of lint. But this kind of improvement on physiological function depended on cultivars and growth stages. The chlorophyll content, NR activity, Pn, F_v/F_o and F_v/F_m of Xinluzao 6 increased with the increasing of nitrogen application at the earlier stages, these indices were maintained at a relatively high in the treatment of N 300kg/hm² at the later stages,but it remained low in the treatment of N 450 kg/hm²,because excessive nitrogen application was apt to result cotton vain growing in full flowering, subsequently led to rapid decline in net photosynthesis rate. Therefore, according to change of varieties and growth stages of cotton, nitrogen application should be moderated, avoid high amount lead to decrease of yields of lint and waste of fertilizer in the later growth stages.