Study on diurnal variations of photosynthesis and response to light of Mesona chinensis

In order to study the photosynthetic characteristics of six germplasm of Mesona chinensis for exploring suitable planting model, LI6400XT portable photosynthesis system was used to measure diurnal dynamics of the photosynthetic characteristics, lightresponse curve of photosynthesis，and chlorophyll content was measured with spectrophotometry. The results showed that stomatal and nonstomatal factors played a positive role in the change of photosynthesis of Sanjia Mesona and Xiaba Mesona, while stomatal factor induced the changes of photosynthesis of the others. Light compensation point (LCP) of six germplasm of Mesona size order is Lingshan smallleafSanjia MesonaXxiaba MesonaPaitan MesonaLingshan bigleafVietnam Mesona and light saturation point (LSP) size order is Lingshan smallleaf Xiaba MesonaVietnam MesonaPaitan MesonaLingshan bigleafSanjia Mesona. Variance analysis shows that LCP and LSP of lingshan smallleaf are much higher than those of other Mesona (P0.05), and it is adaptive to the environment with high level of light intensity. LCP of Vietnam Mesona is lowest (P0.01), showing that it was shadetolerant and attempted to plant under forest. There was a significant positive correlation between chlorophyll content and Pn,max, and daily variation regularity of Pn was caused by environmental factors and internal factors. The study provides theoretical basis for exploring Mesona planting model, reasonable standardized planting and screening of improved strains.