紫荆叶片夏季水分利用效率的日变化

Study on Diurnal Variation of Water Use Efficiency of Cercis chinensis Leaves in Summer

紫荆叶片净光合速率日进程曲线为“双峰”形 ,光合效率午间明显降低 ,主要由非气孔限制引起。蒸腾速率和气孔导度的日变化为“单峰”形 ,午间最高。水分利用效率早晚较高、午间较低。净光合速率、蒸腾速率、气孔导度和水分利用效率与一些环境因子的相关性都达到 0 0 1显著水平。利用多元逐步回归方法分别得到了净光合速率、蒸腾速率、气孔导度和水分利用效率与环境因子的最优方程。

The diurnal variations of net photosynthetic rate(P n),Transpiration rate(T r),stomatal conductance(G s)and water use efficiency(WUE)of Cercis chinensis leaves under natural conditions had been studied.The results were as follows:In summer clear days,the curves of diurnal variations of P n had two peaks,which had an obvious phenomenon of midday decline of photosynthetic efficiency.The mid-depress of P n was principally caused by non-stomatal limited elements.T r and G s had single peak which showed the maxmum at noon.WUE were higher at sooner or later ,and were lower at noon,the correlations,P n,T r,G s and WUE to some environmental factors were all singificant at 0.01 probability level.The most excellent equation of the diurnal variation of P n,T r,G s and WUE were attained by the methods of stepwise multi-regression respectively.