冬小麦光合特征及叶绿素含量对保水剂和氮肥的响应

以不施保水剂和氮（N）肥为对照，测定了保水剂（60 kg·hm^-2）与不同N肥水平（0、225、450 kg·hm^-2）及其配施条件下大田小麦的光合特征、叶绿素含量和水分利用效率等指标，研究了冬小麦拔节期和灌浆期光合生理特征、叶绿素含量及水分利用对保水剂和N肥的响应.结果表明：灌浆期各处理的光合速率、气孔导度、胞间CO₂浓度、叶片水分利用效率及叶绿素含量均大于拔节期.在拔节期，单施N肥条件下，随施N量的增加，单叶水分利用效率提高，光合速率、气孔导度、胞间CO₂浓度及蒸腾速率均先增后减；225 kg·hm^-2 N肥处理的叶绿素含量最高.施用保水剂后，随施N量的增加，胞间CO₂浓度降低，而光合速率等均提高；单施保水剂及其与N肥配施提高了叶绿素含量，而过多N肥效果不显著在灌浆期，单施N肥显著提高了小麦的光合速率及水分利用效率，降低了气孔导度、胞间CO₂浓度及蒸腾速率；叶绿素含量随N肥用量的增加而增加.施用保水剂后，随N肥用量的增加，光合速率和叶片水分利用效率均先增后减，而胞间CO₂浓度和蒸腾速率先减后增，但均低于对照，气孔导度随施N量的增加而提高.单施保水剂的叶绿素含量显著提高，但其与N肥配施叶绿素含量有所降低.保水剂与N肥配合施用显著提高了小麦的千粒重、产量及水分生产效率.其中，保水剂与225 kg·hm^-2N肥配施处理的产量及水分生产效率均最高.

Responses of winter wheat photosynthetic characteristics and chlorophyll content to water-retaining agent and N fertilizer

The effects of water-retaining agent (60 kg·hm^-2) and nitrogen fertilizer (0, 225, and 450 kg·hm^-2) on the leaf photosynthetic characteristics, chlorophyll content, and water utilization of winter wheat at jointing and grain-filling stages were studied under field conditions. In all treatments, the net photosynthetic rate, stomata conductance, intercellular CO₂ concentration, water use efficiency, and chlorophyll content were greater at grain-filling stage than at jointing stage. Under nitrogen fertilization but without water-retaining agent application, the water use efficiency (WUE) of single leaf at jointing stage increased with increasing nitrogen fertilization rate, while the net photosynthetic rate, stomata conductance, intercellular CO₂ concentration, and transpiration rate decreased after an initial increase. The chlorophyll content was the highest under 225 kg·hm^-2 nitrogen fertilization. In the treatments of water-retaining agent application, the intercellular CO₂ concentration decreased with increasing nitrogen application rate, but the net photosynthetic rate, transpiration rate, and WUE increased. The application of water-retaining agent or its combination with nitrogen fertilization increased the chlorophyll content, but excessive nitrogen fertilization had lesser effects. At grain-filling stage, applying nitrogen fertilizer alone significantly increased the net photosynthetic rate and WUE, but decreased the stomata conductance, intercellular CO₂ concentration, and transpiration rate. The chlorophyll content increased with increasing nitrogen application rate. After applying water-retaining agent and with the increase of nitrogen fertilization rate, the photosynthetic rate and WUE decreased after an initial increase, while the intercellular CO₂ concentration and transpiration rate were in adverse but still lower than those without water-retaining agent application. The stomata conductance increased with increasing nitrogen fertilization rate. The chlorophyll content increased significantly under the application of water-retaining agent, but somewhat decreased under the combined application of water-retaining agent and nitrogen fertilizer. The application of both water-retaining agent and nitrogen fertilizer increased the 1000 grain mass, grain yield, and water production efficiency of winter whe at significantly, with the best effect in the treatment of water-retaining agent with 225 kg·hm^-2 nitrogen fertilization.