适度高温下亚热带阔叶树种叶片的光合速率和吸收光能的分配

 利用光合作用测定系统（Li-COR 6400和叶室荧光仪），测定了亚热带阔叶树种的光合速率和荧光参数，分析了38 ℃适度高温对叶片光合作用 和吸收光能分配的影响。测试树种包括华南亚热带地区常见的阳生性树种木荷（Schima superba）、耐荫树种黄果厚壳桂（Cryptocarya concinna）和中生性树种红锥（Castanopsis hystrix）。适度高温处理均引起 所有树种的光合能力下降，而且木荷和红锥下降的程度比黄果 厚壳桂明显。与25 ℃的对照温度相比，适度高温处理的木荷叶片用于光化学反应所消耗的光能下降，红锥和黄果厚壳桂也有相似的反应，表明 适度高温限制叶片用于光化学反应的吸收光能。无论哪个树种，38 ℃适度高温处理的植物，叶片总吸收光能中额外多余的那部分和处于非活化 状态PSⅡ所吸收的那部分光能都增加，而且黄果厚壳桂比木荷和红锥显著，因此，亚热带阔叶森林的树种对适度高温的响应因种类而异。研究 结果意味着将来气候变化导致温度的上升对演替后期树种黄果厚壳桂的光合过程的限制比演替早期的树种木荷和中生性树种红锥会更严重。

PHOTOSYNTHETIC RATES AND PARTITIONING OF ABSORBED LIGHT ENERGY IN LEAVES OF SUBTROPICAL BROAD-LEAF TREES UNDER MODERATELY HIGH-TEMPERATURE

Aims This study aimed at better understanding the physiological mechanisms involved in the moderately high temperature treatment, particularly those relating to partitioning of absorbed light energy in some dominant tree species of low subtropical broad-leaf forest in South China, which would affect vegetation succession.Methods Two-year old saplings of three tree species, Schima superba, Castanopsis hystrix and Cryptocarya concinna, which represent different successional stages in subtropical broad-leaf forest were treated with moderately high temperature (38 ℃). Their photosynthetic rate and chlorophyll fluorescence parameters were measured using a photosynthesis measurement system ( Li-COR 6400 and leaf chamber fluorometer) in order to evaluate the effects of moderately high temperature on photosynthesis and partitioning of absorbed light energy under subsequent irradiance.Important findings Exposure to moderately high temperature caused decrease of photosynthetic capacity of all experimented tree species under the subsequent irradiance, and such decrease was more obvious in sun plant, S. superba and mesophytic plant, C. hystrix than in shade-adapted plant, C. concinna. The fraction of energy consumed by photochemical reaction decreased in the exposed leaves of S. superba, in comparison with those in control at 25 ℃, and a similar response was also found in C. hystrix and C. concinna. The results showed that moderately high temperature could restrict the fraction of absorbed energy utilized in photochemical reaction in leaves treated with moderately high temperature under the subsequent irradiance. The portion of total absorbed light energy that was excessive and the fraction of energy absorbed by the inactive PSⅡ also increased in the exposed leaves at 38 ℃ irrespective of species difference, and the increments were more remarkable in C. concinna than in C. hystrix and S. superba. Different responses to moderately high temperature were dependent on tree species in subtropical broad-leaf forest. The results may mean that the increase of ambient temperature by changing climate would more severely restrict photosynthetic process in the late-successional species, C. concinnia than in the early- or mesophytic species, S. superb and C. hystrix.