4种木本植物叶片的光合电子传递和吸收光能分配特性对光强的适应

以气体交换和叶绿素荧光测定相结合的方法研究了亚热带自然林乔木荷树、黧蒴和林下灌木九节、罗伞幼苗的光合电子传递及激发能利用的分配对生长光强的适应特性。4种植物生长于100%、36%和16%的自然光下8个月，叶片的光化学速率和热能耗散速率随光强增大而提高，热能耗散占总的光能吸收的比例也因光强不同而改变，16%光下的相对热耗散率约为40%～45%,100%自然光下增大至50%～75%。叶片总的非环式电子流速率及其分配到光呼吸的比例在100%光强下最高。乔木和灌木的电子传递和光能分配特性在16%光下相似，在100%光下差别较明显。除灌木种有较高的热耗散比例之外，其余的参数皆比乔木的低。结果表明乔木与灌木皆可通过提高激发能热耗散比例和提高光合电子传递向光呼吸的比例来适应于高光强条件。

The Allocation of Photosynthetic Electron Transport and Absorbed Light Energy in Leaves of Four Woody Plants Acclimated to Different Light Intensities

The characteristics of acclimation in photochemistry, thermal energy dissipation and electron transport to three light intensities in leaves of forest plants were studied by using the combination of gas exchange and chlorophyll fluorescence measurements. The saplings of tree species Schima superba, Castanopsis fissa and understory shrub species Psychotria rubra, Ardisia quinquegona were grown for 8 months under 100%, 36% or 16% of full sunlight. The estimated rates of photochemical reactions, thermal energy dissipation, and percentages of absorbed light dissipating as thermal energy increased with increasing growth light intensity in all four plants (Figs. 2,3), whereas the allocated fraction of absorbed light to photochemistry decreased (Table 2). Photosynthetic electron transport rate (J F) was the highest under 100% sunlight, accompanied by a high partitioning ratio to photorespiration(J O/J F) (Fig.1, Table 1). The changes in values of these parameters of electron transport and energy were similar between tree species and shrub species under deep shade of 16% sunlight, but were different under 100% sunlight (Tables 1,2). All these parameters were higher in tree species than in shrub species, except that a higher fraction of absorbed light was dissipated as thermal energy in shrub species under high light condition. The results indicated that both tree and shrub species from a natural forest could acclimate to high light intensity by increasing the fractions of thermal energy dissipation and electron transport flow through photorespiration.