贡嘎山地区黄背栎光合作用日变化及光合响应

Photosynthetic Diurnal Variations and Photosynthetic Responses of Quercus pannosa in Gongga Mountains

使用Li-6400便携式光合作用测定系统,研究了自然条件下黄背栎光合作用日进程及光合响应.结果表明:(1)晴天叶片净光合速率日变化为比较平缓的单峰曲线,无光合'午休'现象,峰值出现在14:00左右,为7.15μmol·m-2·s-1,净光合速率日变化趋势与光合有效辐射和叶片气孔导度的变化一致,与大气CO2体积分数和叶片的胞间CO2体积分数的日进程相反;(2)随着CO2体积分数的增加,叶片对光合有效辐射的利用效率增加,光饱和点、弱光下光量子利用效率和最大净光合速率均增加,而光补偿点和暗呼吸速率降低,较高的CO2体积分数可增强植物对强光的适应性,抑制暗呼吸作用.3种CO2体积分数下测得的黄背栎光饱和点为1 486～1725μmol·m-2·s-1,光补偿点为46～76μmol·m-2·s-1,表观量子效率为0.025 41～0.029 69;(3)随着光合有效辐射的增加,光合速率在一定范围内随CO2体积分数的增加而增加,气孔导度随CO2体积分数的增加而降低.CO2饱和点为1 000～1 200μmol·mol-1,羧化效率为0.0149～0.0420.

Diurnal variation of photosynthesis and photosynthetic response of Quereus pannosa were studied using the Li - 6400 portable photosynthesis system. Results showed that the diurnal variation of net photosynthetic rate （ P, ） in the sunshine is a smooth one - peak curve and has no midday depression. The peak value appears at 14：00 with 7.15 μmol·m^-2·s^-1 The diurnal variation of net photosynthetic rate （Pn） is in agreement with that of photosynthetic active radiation （RPh） and stomatal conductance, but opposite with the air CO2 concentration and the intercellular CO2 concentration （Ci）. With increasing CO2 concentration, the use efficiencyies of leaves to photosynthetic active radiation increase gradually, and the light saturate point （P1s）, apparent quantum utilization efficiency （α） and maximum net photosynthetic rate （Pmax） also increase, but the light compensate point （PLC） and the clark respiration rate （Rd） decrease. The increasing of CO2 concentration can extend the adaptability of plants to strong radiation and restrain the clark respiration. The P1s of Q. pannosa under different CO2 concentrations changes between 1 486 and 1 725 μmol · mol^-1, and Pl.s between 46 and 76 μmol · mol^-1, a between 0.025 41 and 0.029 69. When photosynthetic active radiations increase, the Pn of leaves increases with increasing CO2 concentrations to a certain extent, but the stomatal conductance decreases. The CO2 saturate point ranges from 1 000 μmol · mol^-1 to 1 200 μmol · mol^-1 , and the earboxylation efficiency from 0.014 9 to 0.042.