芦苇(Phragmites communis)光合作用与蒸腾作用的日进程

DIURNAL PROCESS OF PHOTOSYNTHESIS AND TRANSPIRATION OF PHRAGMITES COMMUNIS

测定了野生芦苇（Ｐｈｒａｇｍｉｔｅｓｃｏｍｍｕｎｉｓ）光合作用、蒸腾作用及相关指标的日变化。叶片的净光合作用率在１０∶００～１５∶００间保持一个高的稳定阶段，平均为７３～９９μｍｏｌＣＯ２·ｍ－２·ｓ－１，光饱和状态下的最大值为１２７μｍｏｌＣＯ２·ｍ－２·ｓ－１，处于挺水植物的低限。蒸腾作用强度的峰值达４８ｍｍｏｌＨ２Ｏ·ｍ－２·ｓ－１。光合作用和蒸腾作用的日进程均未发生“午休”现象；相反，二者都是在正午前后强度最大。光合光量子流密度与净光合作用率、蒸腾强度、叶面传导率均存在不同程度的正相关。芦苇的光合作用强度和水分利用效率相对较低，但年生产量却较高，这是因为芦苇具有密实的叶子、有利的叶片配置结构和高的蒸腾作用强度。

Diunal changes in photosynthesis,transpiration,and the related indexes of Phragmites communis were measured.Net photosynthetic rate per unit leaf area maintained on a high plateau (average 7.3～9 9μmolCO 2·m -2 ·s -1 ) from 10∶00～15∶00and reached a peak of 12.7μmolCO 2·m -2 ·s -1 at light saturation,which is in the lower range for emergent plants.The maximum transpiration rate was 4.8 mmolH 2O·m -2 ·s -1 .The daily courses of net photosynthesis and transpiration had no midday depression;on the coutrary,their peak values were recorded around noon.Positive correlations occurred between photosynthetic photon flux density and net photosynthetic rate,transpiration rate,an well as leaf conductance.The photosynthesis and water utilization efficiency are relatively lower,but annual production is rather high,which is attributed to the dense leaf,proper assemblage of leaves ,and high transpiration.