当归叶片光合参数日变化及其与环境因子的关系

在当归根茎膨大期,利用CI-310便携式光合仪,田间活体测定了当归的净光合速率(Pn)、蒸腾速率(Tr)、气孔导度(Gs)、胞间CO2浓度(Ci)等光合生理生态因子,以及光合有效辐射(PAR)、田间CO2浓度(Ca)、相对湿度(RH)、大气温度(Ta)、叶温(TL)等环境因子的日变化。结果表明,当归Pn日变化曲线为"双峰"型,最高峰出现在10:00左右,次高峰出现在16:00左右,午间有明显的"午休"现象,气孔因素是导致其"午休"的主要原因。Tr、Gs和Ci的日变化曲线均为"双峰"型,最高峰出现在10:00,次高峰出现在17:00。当归叶片净光合速率随环境因子日变化最优逐步多元回归方程为yPn=14.3108 0.0076xPAR-0.5271xTL(R2=0.6601,P<0.05),TL和PAR是对光合速率直接影响最大的生态因子,而Ca、RH和Ta主要是通过TL而间接影响光合速率的变化。

Diurnal Dynamics of Photosynthetic Parameters in Leaves of Angelica sinensis and Its Relation to Environmental Factors

During the rootstock thickening period,the diurnal dynamics of photosynthetic rate(Pn),transpiration rate(Tr),stomatal conductance(Gs) and internal CO2(Ci) of Angelica sinensis as well as the ecological factors photosynthetically active radiation(PAR),CO2 concentration in field(Ca),relative humidity(RH),air temperature(Ta) and leaf temperature(TL) were measured.The results show that the diurnal net photosynthetic rate of A.sinensis in sunny day exhibited double-peak pattern,and the peaks occurred at 10:00 and 16:00 respectively.There was a significant midday depression with A.sinensis,which was caused principally by stomatal factors such as stomatal conductance.The curves of diurnal variation in Tr,Gs and Ci of A.sinensis leaves had two peaks also,the peaks occurred at 10:00 and 17:00 respectively,and an obvious midday depression from noon to 1pm.The most optimal equation describing diurnal variation of Pn was attained by the method of stepwise multiple-regression as follows:yPn=14.310 8 0.007 6xPAR-0.527 1xTL(R2=0.660 1,P<0.05).With analysis of partial correlation and path on Pn and environmental factors,it is concluded that TL and PAR had the greatest effect on the diurnal dynamics of Pn,while Ca,RH and Ta indirectly affected Pn mainly through TL.