施氮量对小麦叶片硝酸还原酶活性、一氧化氮含量和气体交换的影响

研究了不同施氮量对冬小麦分蘖到抽穗期叶片硝酸还原酶(NR)活性、一氧化氮(NO)含量、气体交换参数和籽粒产量的影响.结果表明:叶片光合速率（P_n）、蒸腾速率（T_r）、瞬时水分利用效率（IWUE）和产量均随施氮量的增加呈先升高后降低的趋势，在180 kg·hm^-2氮处理时达到最高.随施氮量的增加，叶片NR活性提高; 在分蘖期和拔节期，叶片NR活性与NO含量呈显著线性相关（R²≥0.68，n=15），NO含量和气孔导度（G_s）呈显著正二次相关（R²≥0.43，n=15）;低氮处理下，NR活性较低使叶片NO含量维持在较低水平，促进气孔开放，高氮处理下，NR活性较高使叶片NO含量增加，诱导气孔关闭；在抽穗期叶片NR活性和NO含量无显著相关关系，虽然NO含量和G_s也呈显著正二次相关（R²≥0.36，n=15），但不能通过施氮提高NR活性来影响叶片NO含量，进而调节叶片气孔行为.合理施氮使小麦叶片NO含量维持在较低水平，可提高叶片G_s、T_r和IWUE，增强作物抗旱能力,促进光合作用，提高小麦产量.

Effects of nitrogen application rate on nitrate reductase activity, nitric oxide content and gas exchange in winter wheat leaves.

In this paper, the effects of different nitrogen application rates on the nitrate reductase (NR) activity, nitric oxide (NO) content and gas exchange parameters in winter wheat (Triticum aestivum L.) leaves from tillering stage to heading stage and on grain yield were studied. The results showed that the photosynthetic rate (P(n)), transpiration rate (T(r)) and instantaneous water use efficiency (IWUE) of leaves as well as the grain yield were increased with increasing nitrogen application rate first but decreased then, with the values of all these parameters reached the highest in treatment N180. The NR activity increased with increasing nitrogen application rate, and there was a significant linear correlation between NR activity and NO content at tillering and jointing stages (R2 > or = 0.68, n = 15). NO content had a quadratic positive correlation with stomatal conductance (G(s)) (R2 > or = 0.43, n = 15). The lower NO content produced by lower NR activity under lower nitrogen application rate promoted the stoma opened, while the higher NO content produced by higher NR activity under higher nitrogen application rate induced the stoma closed. Although the leaf NO content had a quadratic positive correlation with stomatal conductance (R2 > or = 0.36, n = 15), no remarkable correlation was observed between NR activity and NO content at heading stage, suggesting that nitrogen fertilization could not affect leaf NO content through promoting NR activity, and further more, regulate the stomatal action. Under appropriate nitrogen application the leaf NR activity and NO content were lower, G(s), T(r) and IWUE were higher, and thus, the crop had a better drought-resistant ability, higher P(n), and higher grain yield.