热带雨林剑叶凤尾蕨(Pteris ensiformis)对光强变化的适应

野外调查表明剑叶凤尾蕨能适应不同的光环境，本研究测定剑叶凤尾蕨在两种不同光环境下的适应能力，在热带雨林林下和林窗生长40d后，林下生长的剑叶凤尾蕨比林窗生长的植株有较多的叶片数，大的冠幅，高的叶绿素含量和表观量子效率。同时。林下生长的剑叶凤尾蕨有高的光化学效率和较低的非光化学耗散能力，这说明低光植物表现出有较高的能量转换能力，而两种光强生长的剑叶凤尾蕨最大光合放氧速率相似。这可能与在高光下的非辐射耗散的提高和光合机构的损伤有关，研究结果表明，剑叶凤尾蕨通过光合器官的调整对不同光强的适应。以促进剑叶凤尾蕨在不同光环境的生长能力。

Acclimation to Light Environment Changes of a Tropical Rainforest Fern,Pteris ensiformis

Investigations of field showed that Pteris ensiformis has the ability to acclimate to different light levels. This study investigated the ability of individuals of Pteris ensiformis to acclimate to low and high irradiance. Plants were cultivated in understory and gap of tropical primary rainforest for about 40 days. Individuals growing in understory indicated more number of leaves, bigger canopy width, higher chlorophyll contents and higher photosynthetic rates than that of plants growing in forest gap. Plants growing in understory also exhibited a greater efficiency in the photochemical utilization of absorbed light energy and lower ability to dissipate excess energy nonphotochemically, relative to the plants growing in forest gap. However, maximum photosynthetic rates were similar in both sets of plants, reflecting the higher efficiency of energy conversation in the understory growning plants and an apparent saturation of photosynthetic capacity in the gap growing plants. The latter may have resulted from the injury of the photosynthetic apparatus in addition to an increase in nonphotochemical dissipation of excess light energy. The higher capacity for harmless thermal dissipation of excess light energy should be beneficial in plants growing in exposed locations and subject to drought and nutrient stresses. Thus, the results expanded those plasticity in adjusting the photosynthetic apparatus to various light levels constitutes a valuable adaptation to growing in different light environments in the tropical rainforest.