藏东南高山林线树种冷杉光合生理特征

Photosynthetic Physiological Characteristics of Abies georgei var.smithii in Sub-alpine Timberline Ecotone of Southeast Tibet

采用L i—Cor—6400光合作用测定系统,对藏东南色季拉山高山林线树种急尖长苞冷杉(Abies georgei var.smithii)的光合作用进行了测定。结果表明:在自然环境条件下的急尖长苞冷杉光合日进程表现为双峰型曲线,在9:30左右达到最高峰,次高峰出现在15:30,其光合作用存在明显的"午休"现象;胞间CO2摩尔分数值随着净光合速率的下降而下降,气孔因素是导致"午休"的主导因素;叶片的气孔导度、蒸腾速率与水分利用效率的日变化进程均呈双峰曲线,并且气孔导度、蒸腾速率与净光合速率三者间有较强的正相关关系。与同一地区其他针叶树种林芝云杉(Picea likiangensis)相比较,急尖长苞冷杉的净光合速率较大,最大值为6.0μmol.m-2.s-1,高于林芝云杉的3.0μmol.m-2.s-1。

An experiment was conducted to study the photosynthesis of Abies georgei var. smithii in sub-alpine timberline ecotone of southeast Tibet using Li-Cor 6400. Results show that the diurnal net photosynthetic rate of A. georgei vat. smithii on sunny days can be expressed with a bimodal curve. The peaks occur at 9：30 and 15：30 respectively. There is an obvious midday depression phenomenon. Intercellular CO2 concentration between cells decreases with the decrease of net photosynthetic rate, and stomatal factors contribute to the midday depression phenomenon. The diurnal changes in stomatal conductance, transpiration rate and water use efficiency also exhibit bimodal curves. The net photosynthetic rate is highly positive correlated with transpiration rate and stomatal conductance. Compared with other conifer species in the same area such as Linzhi spruce, the net photosynthetic rate of A. georgei var. smithii is higher, and its maximum value is 6.0 μ mol m^ -2 ·s^-1 , while the maximum net photosynthetic rate of Linzhi spruce is 3.0 μmol ＂ m^-2 · s^-1.