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

利用CO2气体交换和叶绿素荧光法,研究了适度高温(38℃)下亚热带森林4种建群树种叶片叶肉导度(gm).结果表明:阳生或早期演替树种荷木叶片gm较中后期演替的中生性或耐荫树种红椎、藜蒴和黄果厚壳桂高(P<0·05).生长在全日光下的叶片gm亦较遮荫的高(P<0·05).温度从25℃升至38℃,4个树种的平均叶肉导度Q10值为(1·59±0·27).gm对温度的响应依赖于植物种类和光环境.由于CO2在水中扩散的Q10值为1·25,gm除受温度影响外,还受到蛋白质的调控.适度高温可引起gm上升,导致叶绿体羧化部位的CO2浓度和羧化速率增高.无论是全日照还是遮荫处理,与荷木相比,适度增温可显著提高红椎、藜蒴和黄果厚壳桂叶绿体羧化速率,说明适度高温对演替中后期树种的演替进程有利.

Responses of mesophyllic conductance in leaves of 4 dominant subtropical forest tree species to moderate high temperature

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.