长期遮光对冬小麦群体及单叶光合特性的影响

目的]研究长期弱光对冬小麦（Triticum aestivum L.）群体光合速率（CAP）以及上3叶特别是旗叶光合特性的影响。方法]以耐弱光性不同的冬小麦品种扬麦158和扬麦11为材料,设不遮光（S0）、从拔节至成熟期遮去小麦冠层自然光强的22%（S1）和33%（S2）3个处理,测定小麦CAP、上3叶的光合速率（Pn）、旗叶叶绿素含量以及籽粒产量。结果]扬麦158和扬麦11 CAP随遮光强度的增强而显著下降;长期弱光下,旗叶Pn显著下降,倒2叶Pn无明显变化,而倒3叶Pn则显著上升,从而部分地补偿了旗叶Pn的降低。该补偿效应因遮光强度和品种而异：S1处理的补偿效应大于S2处理,扬麦158的补偿效应大于扬麦11。在旗叶光合速率高值持续期内,长期遮光降低了扬麦158和扬麦11总叶绿素、叶绿素a和b的含量,以及叶绿素a/b值。结论]弱光下,旗叶叶绿素a含量以及叶绿素a/b值下降引起其Pn显著降低,从而使得CAP明显降低,最终导致籽粒产量显著下降。该研究可为长江中下游地区的小麦生产提供重要的理论依据。

Effects of Long-term Shading on Canopy and Single Leaf Photosynthetic Properties of Winter Wheat( Triticum aestivum L.)

Objective] The aim was to study the effects of long-term low radiation on canopy apparent photosynthesis(CAP) and photosynthetic properties of the top three leaves of winter wheat,especially the flag leaf.Method] Two winter wheat cultivars,differing in shading(low radiation) tolerance,Yangmai 158 and Yangmai 11 were shaded to evaluate the impacts of low radiation on CAP and photosynthetic properties of the top three leaves,chlorophyll content of the flag leaf and grain yield.Three treatments were designed as non-shading(S0),22% less intercept radiation(S1) and 33% less intercept radiation(S2) from jointing to maturity.Result] With shading intensity enhancing,CAP of both cultivars dropped significantly,while net photosynthetic rate(Pn) of flag leaf decreased significantly,no obvious effect on Pn of the second leaf from the top and significantly increased in that of the third leaf.The decrease of Pn in flag leaf was partially compensated by the increase of Pn in the third leaf.The compensation efficiency changed in different shading intensity and cultivars:It was greater in S1 than that in S2,while greater in Yangmai 158 than that in Yangmai 11.Long-term shading declined total chlorophyll,chl a and b content and chl a/b value of flag leaf in its photosynthetic active duration.Conclusion] Shading between jointing and maturity reduced chl a and chl a/b of flag leaf and then to its Pn.Thus,the CAP was decreased,which resulted in significant decline in grain yield.This research provides an important theoretical basis for wheat production in the middle-down area of the Yangtze River.