中文摘要：

对不同氮肥水平下冬小麦叶片光合速率的日变化规律进行了研究，结果表明：增大氮肥的施用量可以提高冬小麦叶片的光合能力。在各种氮肥水平下，冬小麦叶片的光合作用均存在“午休”现象，而“午休”现象的产生是“气孔因素”与“非气孔因素”共同作用的结果。其中“气孔因素”则是温度造成蒸腾作用增强，气孔对蒸腾作用的反馈抑制造成的。光合速率对光强的响应在上午和下午存在明显差异，上午利用光能的能力明显大于下午。这主要表现的在上午的表观初始量子效率比下午大，而表观暗呼吸速率比下午低。光合产物对光合作用的反馈抑制会造成这种量子效率的差异性；而下午比上午的温度高则会造成下午的呼吸作用更大。无论是气孔限制、光合产物反馈抑制还是温度对呼吸作用的影响都可能是导致光合速率在上午和下午异步性的主要原因。

英文摘要：

The experiments on diurnal photosynthesis of winter wheat leaf with different nitrogen rates were conducted. The results indicated that the photosynthesis of winter wheat leaf increased with different nitrogen levels, but with obvious photosynthesis down-regulation at noon affected by both stomatal limitations. The stomatal limitation is caused by stomatal feedback to the increased transpiration under high temperature. The response of photosynthesis to light intensity in the morning was different from that in the afternoon. Higher light use efficiency and larger initial quantum efficiency in the morning are resulted from the feed- back of photosynthesis. The respiration is higher because the temperature is higher in the afternoon. The above factors such as stomatal limitation, the down-regulation of photosynthesis and the effects of respiration all can be factors for the hysteresis response of photosynthesis to light intensity.