Abstract:

To study the photosynthesis and its relationships with environmental factors of Ixeris chinensis (Thunb.) Nakai, photosynthetic characteristics of I. chinensis and photosynthetic active radiation (PAR), atmospheric CO2 concentration (Ca), ambient temperature (Ta), leaf temperature (Tl) and relative humidity (RH) were measured by TPS-1. Result showed: diurnal variation of net photosynthetic rate of I. chinensis could be expressed as two-hump curves, reflecting an obvious middy depression at noon, and the maximum values that appeared at 10:00 and 14:00 were 9.26 and 4.17 μmol/(m2?s), respectively, the stomatal limitations were responsible for photosynthetic decline of I. chinensis in the midday; the diurnal variation of transpiration rate was single peak curve, and the maximum value that appeared at 10:00 was 3.52 mmol/(m2?s), the variations of stomatal conductance and water use efficiency were two-hump curves with the peaks appeared at 10:00 and 14:00; the direct effects of environmental factors to Pn were the order of TL>PAR>Ta>Ca>RH, there was a significantly and positively correlation between the Pn and PAR, RH (P<0.05), and negative correlation with Ta and TL. In the diurnal dynamics of gas exchange, effects of environmental factors on photosynthetic physiological parameters of I. chinensis were different. In a word, PAR, Ta and RH were main environmental factors to influence photosynthetic gas exchange of I. chinensis.