不同生态习性热带雨林树种的幼苗对光能的利用与耗散

研究了生长于100％、25％和8％光照条件下的热带雨林先锋树种团花、演替顶极阶段的冠层树种绒毛番龙眼和中下层树种滇南风吹楠幼苗的光合能力及光能分配特性对光强的响应。与绒毛番龙眼和滇南风吹楠相比，团花具有较高的最大光合速率和最大电子传递速率，从光能分配对光强的响应曲线可以看出，随着光强的增加，3个树种幼苗叶片吸收的光能分配到光化学反应的比例减少，分配到热耗散的比例增加，光能在光化学反应与热耗散之间的分配呈显著负相关，与其它两个种相比，100％光下的团花幼苗将较多的光能分配到光化学反应中，热耗散较弱且未达到饱和。过剩光能少，没有引起长期光抑制，绒毛番龙眼和滇南风吹楠将叶片吸收的较多光能分配到热耗散中，但生长于100％光下的幼苗过剩光能仍然较多，导致幼苗遭受长期光抑制，结果表明，不同生态习性热带雨林树种幼苗更新对光环境的要求与这些幼苗对光能的利用和耗散特性密切相关。

Light energy utilization and dissipation in seedlings of three tropical rain forest tree species with different ecological habits

In this study,the light energy allocations between photochemical reactions and heat dissipation in the seedlings of three tropical rain forest tree species were investigated under three light regimes (100%,25% and 8% of full sunlight) by using chlorophyll fluorescence technique.These tree species are Anthocephalus chinensis (Rubiaceae),a pioneer species,Pometia tomentosa (Sapindaceae),a canopy climax species,and Horsfieldia tetratepala (Myristicaceae),a sub-canopy climax species.Under the same light levels,A.chinensis had a higher maximum photosynthetic rate (P max) and maximum electron transport rate (ETR max) than P.tomentosa and H.tetratepala.From the light response curves of light energy allocations,all test species had a decreased fraction of light energy allocated to photochemical reactions,while the fraction of light energy allocated to heat dissipation was increased with light intensity.The fractions of light energy allocated to photochemical reactions and heat dissipation were negatively correlated with very high significance.Compared to other two species,A.chinensis allocated more light energy to fractions of photochemical reactions,and had weaker and unsaturated heat dissipation.But,when growing under 100% sunlight,this species had less excess light energy to be used for photosynthesis,so that,it did not suffer from photoinhibition.In contrast,more light energy was allocated to fractions of heat dissipation in both P.tomentosa and H.tetratepala seedlings.Growing under 100% sunlight,these two species received more excess light energy,which caused photoinhibition.Our results support the idea that light requirements for the regeneration of three tropical tree species under different ecological habits are related to their characteristics of light energy utilization and dissipation.