紫椴幼树叶片的光合作用特征

对生长于不同光照环境中紫椴幼苗叶片光合作用的光响应动态研究结果表明，适度遮荫环境中的幼苗叶片平均光饱和光合速率和平均光饱和水分利用效率高于全光环境个体，蒸腾速率和暗呼吸速率则低于后者，受强度遮荫的幼苗各指标均处于最低水平。在生长高峰期，全光和强度遮荫环境中的个体叶片暗呼吸速率占净光合速率的80%以上，受一层网遮荫个体的暗呼吸速率只占净光合速率的38.3%。表观量子产额测定结果表明，紫椴幼苗叶片光合作用对光的需求量相对较低，当紫椴幼苗处于强光环境中时，幼苗必须采取某种对策避免吸收过量的光能，或者通过某种方式耗散过剩的热能。综合叶片的光合作用特征，认为在生长高峰期的高呼吸消耗是全光环境中紫椴幼苗枝干生长量小、生物量积累相对低的主要原因，光照不足是强度庇荫环境中紫椴幼苗枝干生长量小、生物量积累相对低的主要原因。

Leaf Photosynthetic Characteristics of Tilia amurensis Seedling

Leaf photosynthetic characteristics of Tilia amurensis seedlings which adapted to different. light environments were analyzed in the peper. Results showed that the average light-saturated net photosynthetic rate and the average light-saturated water use efficiency of seedling leaves which shaded by one layer of shade net was much higher than that of sun seedlings. Bat the transpiration rate and dark respiration rate of the shaded seedlings was obviously lower than that of the sun seedlings. The photosynthetic indices of seedling leaves which suffered to hem shade. mentioned above. was the least. The dark respiration rate took beyond 80% of net photosynthetic rate for seedlings adapted to full sunlight. and heavy shade environment, while the dark respiration rate only took 38. 3% of net photosynthetic rate for seedlings growing in moderate shade environment. By comparison of apparent quantum yield between the linden and other plants. the authors suggested that the amour linden photosynthesis need less PAR. Thus the seedlings must dissipate excess radiation energy so as to ensure normal leaf physiological metabolism when the seedlings exposed to high light. By analyzing integrate photosynthetic characteristics of the linden. the authors concluded that high respiration consumption in speed growth period was the main reason of lower branch and bole increment and lower biomass accumulation to seedlings exposed to full sunlight. And insufficient PAR was the main reason of lower branch and bole increment and lower biomass accumulation to seedlings growing in heavy shade environment.