灌水对小麦旗叶光合功能衰退的影响

利用田间小区试验研究了不同灌水对冬小麦旗叶光合功能衰退的影响。研究表明：小麦旗叶光合衰退初期引起光合下降的原因主要是气孔限制，后期则为非气孔限制。灌水可提高旗叶光合速率，并使由气孔限制非气孔转变的时间推后，同时，还可增加叶绿素含量，增强根活力，使小麦旗叶光合功能持续期延长，过量灌水改善旗叶光合速衰的效果主要表现在后期，对产量提高的意义并不大。

Effect of irrigation on photosynthesis decline of wheat leaf during senescence

Effect of irrigation on photosynthesis decline of winter wheat flag leaf during senescence was studied with field plot experiment.The results indicated that,the main reason of the decrease of photosynthetic rate at the initial stage of senescence was due to stomatal limitation but nonstomatal limitation thereafter.Irrigation could not only raise photosynthetic rate of flag leaf but also delay the turn time from stomatal limitation to nonstomatal limitation.Meanwhile,chlorophyll content increased,root activity enhanced,and photosynthesis lasting period prolonged.The role of overirrigation improving photosynthesis decline of flag leaf was mainly at the latter stage and had no role for yield increase.