摘要
研究了在沙漠地区典型的高温低湿条件下，沙冬青的气体交换特征。结果表明：沙冬青叶片具有典型的双峰净光合速率曲线，即在中午表现出气孔关闭并伴随着光合速率的大幅度下降。但中午光合速率下降期间，沙冬青叶片胞间ＣＯ２浓度不但没有下降，反而大幅度增加（９∶００－１０∶００），继而保持相对稳定（１０∶００－２０∶００）。同时气孔导度和气孔限制值也下降，日变化幅度小，且终日低下，这与沙冬青冠层的ＶＰＤ和气温密切相关。我们认为沙冬青净光合速率下降的决定因素是叶肉细胞的光合活性，但沙冬青在中午气孔导度的下降不是造成光合午休的主要原因，而是在沙漠干旱环境中实现水分利用最优的对策。
he gas exchange characteristics of A.mongolicus grown in desert region of Ningxia,was studied under natural condition by using a portable Li6200 gas analysis system.It was found that the photosynthetic rate of A. mongolicus leaves displayed significant twopeaked diurnal courses on hot,bright sunny days,in the other words,displayed a strong depression of photosynthesis and the simultaneous stomatal closure at midday.But the intercellular CO2 concentration (Ci) increased rapidly (9∶00-10∶00) instead of decreasing,then was in steady state.At same time,stomatal conductance (Cs) and stomatal limiting value (Ls) also declined,their diurnal course was very low throught a day.The diurnal course of stomatal conductance was resulted in VPD and air temperature in canopy of A.mongolicus without corresponding to incident radiation.On the basis of analysis of stomatal limitation of photosynthesis using two criteria (intercellular CO2 concentration and stomatal limiting value) suggested by Farquhar and Sharkey (1982),it is concluded that the predominant limiting factor of photosynthesis in A.mongolicus is the photosynthetic capacity of mesophyll cells.The stomatal closure at midday in A.mongolicus leaves caused by high VPD and high temperature was not the cause of midday depression of photosynthesis but was a strategy of realize optimal water use under desert region.
出处
《西北植物学报》
CAS
CSCD
1998年第2期207-213,共7页
Acta Botanica Boreali-Occidentalia Sinica
关键词
沙漠地区
沙冬青
气体交换特点
desert region,Ammopiptanthus mongolicus,gas exchange characteristics,stomatal and nonstomatal limitation
