Responses of mesophyllic conductance in leaves of 4 dominant subtropical forest tree species to moderate high temperature
亚热带森林四种建群树种叶片叶肉导度对适度高温的响应

By using CO2 exchange system and chlorophyll fluorescence method, the magnitude of mesophyllic conductance (g(m)), namely the CO2 transfer conductance from intercellular space to chloroplast, in the leaves of four dominant subtropical forest tree species under moderate high temperature (38 degrees C) was studied. The results revealed that sun or early-successional species Schima superba had a higher g(m) than mesophytic and shade-tolerant species, such as Castanopsis hystrix, C. fissa and Cryptocarya concinna, and the leaves under full direct light had a higher g(m) than those under shade. The average g(m) of the four test trees from 25 degrees C to 38 degrees C was 1.59 +/- 0.27, and the responses of g(m) to temperature were dependant on the tree species and their leaf type (sun or shade leaves). Because the diffusion of CO2 in water was only about 1.25, g(m) might be controlled by a protein-related process besides temperature. Moderate high temperature could increase the g(m) value, resulting in the increase of CO2 concentration and carboxylation rate in chloroplasts. Comparing with that of S. superba, the carboxylation rate of C. hystrix, C. fissa and C. concinna was significantly increased by moderate high temperature, regardless of under full direct light or shading, indicating that moderate high temperature would favor the succession of mid- and late-successional species.