长果安息香夏季光合蒸腾日变化与其环境因子的关系

Photosynthesis and transpiration characteristics of Changiostyrax raxdolichocarpa and their relations with environmental factors

长果安息香是稀有濒危植物,国家II级保护植物。为探明长果安息香光合蒸腾特性与其环境因子的关系,在夏季晴朗天气下,利用Li-6400光合测定仪测定了4年生长果安息香的净光合速率(Pn)、蒸腾速率(Tr)、气孔导度(Gs,X1)、气温(Ta,Xs)、光合有效辐射(PAR,X3)、空气相对湿度(RH,X4)、大气CO2浓度(Ca,X5)以及胞间CO2浓度(Ci,X6)的日进程。结果表明:长果安息香Pn与Tr日进程曲线均呈"双峰型",有明显的光合"午休"现象,且主要是由于气孔限制因素引起的;水分利用率(WUE)在早、晚较高并在中午出现一次回升;应用逐步多元回归的方法得到了长果安息香的Pn和Tr日变化的最优方程:Y(Pn)=32.719+0.001X3+5.554X1-0.058X5-0.251X2(复相关系数R=0.681,F=44.204,P<0.01,标准估计误差Se=0.942);Y(Tr)=4.613+12.353X1-0.057X4-0.002X6(复相关系数R=0.913,F=341.779,P<0.01,标准估计误差Se=0.287)。通径分析结果表明,PAR、Gs、Ca、Ta与长果安息香Pn的日变化呈极显著或显著的相关关系,是长果安息香Pn的主要影响因子,直接效应的顺序为Ca>Ta>PAR>Gs,总效应顺序为Ta>Ca>Gs>PAR;Gs、RH、Ci是长果安息香Tr的主要影响因子,直接效应和总效应的顺序均为Gs>RH>Ci。

Changiostyrax raxdolichocarpa C.T. Chen, a rare and endangered species, is a ornamental plant ranged as the national second class protection species. In order to study the photosynthesis and transpiration characteristics of C. raxdolichocarpa and their relations with environmental factors, in a clear day at summer, the diurnal variations of net photosynthetic rate （Pn）, transpiration rate （Tr）, stomatal conductance （Gs, X1）, air temperature （Tr）（2）, photosynthetic effective radiation （PAR, X3）, air relative humidity （RH, X4）, air CO2 concentration （Ca, X5） and intercellular CO2 concentration （Ci, X6） of C. raxdolichocarpa were determined by using Li-6400 Portable Photosynthesis Measurement System. The results show that the curves of Pn and Tr had respectively two peaks with an obvious decline of Pn at noon and the midday depression of Pn was mainly influenced by the stomatal factors; The water use efficiency （RWUE） was higher at early morning and at dusk, and had a little raise at noon. The optimized equations of the diurnal variations of Pn and Tr were calculated respectively by the method of stepwise multiple regression as follows： Y（Pn）=32.719＋0.001X3＋5.554X1-0.058X5-0.251X2 （R=0.681, F=44.204, P 〈 0.01, Se=0.942）, Y（Tr）=4.613＋12.353X1-0.057X4-0.002X6 （R=0.913, F=341.779, P 〈 0.01, Se =0.287）. The path analysis indicates that the Pn had significant correlations with X3, X1, X5 and X2. X3, X1, X5 and X6 were the main environment factors affecting the Pn and they ranked by the direct path coefficient as X5 〉 X2 〉 X3 〉 Xt, or ranked by the total path coefficient as X2 〉 X5 〉 X1 〉 X3. X1, X4 and X6 were important environment factors affecting the Tr and the significant correlations were observed. The affecting ability of X1 on Tr was the highest, followed by X4 and X6.