干旱胁迫下5种幼苗光合特性的研究

以该区年龄相同的5种主要植被恢复树种车桑子、滇柏、侧柏、花椒和香樟幼苗为研究对象，通过盆栽控水试验，测算其在不同水分梯度下的叶绿素相对含量、净光合速率、蒸腾速率、气孔导度、胞间CO₂浓度以及水分利用效率等生理生态指标，系统比较各参数的适应性变化及其差异性分析，结果表明：（1）随着干旱胁迫的加剧，5种幼苗叶片叶绿素相对含量呈现不同的变化趋势，车桑子逐渐降低，侧柏和滇柏先降后升，花椒和香樟先升后降；（2）各光合生理生态参数也呈现不同的变化规律：随干旱胁迫的加剧，净光合速率、蒸腾速率、气孔导度均逐渐降低，且在中度和重度干旱胁迫时极显著降低，其中在重度干旱胁迫时，侧柏的净光合速率最低比对照下降了100.5%，下降幅度最大；胞间CO₂浓度在轻度干旱胁迫时下降，中度和重度干旱胁迫时上升；水分利用效率在轻度和中度干旱胁迫时增加，重度干旱胁迫时下降，其中香樟的水分利用效率在重度干旱胁迫时仍是对照的1.05倍；（3）综合分析各项生理生态参数，5种幼苗均能耐受一定程度的干旱胁迫，但香樟的控水耐旱能力明显高于其它4种树种，更能适应石漠化地区的生态环境。

Studies on Seedling Photosynthetic Characteristics of Five Tree Species under Drought Stress

In order to provide theoretical basis for vegetation restoration in rocky desertification district, the seedlings of 5 tree species, Dodonaea viscosa (Linn.) Jacq., Fokienia hodginsii (Dunn) Henry et Thomas, Platycladus orientalis (Linn.) Franco, Zanthoxylum bungeanum Maxim, and Cinnamonum camphora L. with same age in the district were used as study objects, through potted water control experiments, to measure and calculate the chlorophyll content, net photosynthetic rate, transpiration rate, stomatal conductance, intercellular CO₂ concentration, water use efficiency, and some other physiological and ecological index, and the adaptabilities and differences among the 5 tree species under different moisture gradients were compared. The results are as follows. (1) With the increasing drought stress, the chlorophyll content of 5 tree species changed in different levels, D. viscosa showed a trend of gradually reducing, P. orientalis and F. hodginsii showed a trend of decrease and then increase, while Z. bungeanum and C. camphora showed a trend of increase and then decrease; (2) The physiological and ecological parameters expressed different variation: the net photosynthetic rate, transpiration rate, and stomatal conductance showed decreasing trends, and under moderate and severe drought stress, they reduced significantly, the net photosynthetic rate of P. orientalis decreased by 100.5%, which was the sharpest decline under severe drought stress; the intercellular CO₂ concentration dropped under mild drought stress, while increased under moderate and severe drought stress; the water use efficiency increased under mild and moderate drought stress, but decreased under severe drought stress; the water use efficiency of C. camphora decreased under severe drought, but still 1.05 times that of the contrast. (3) Based on a comprehensive analysis of the physiological and ecological indexes, it showed that all the seedlings could tolerate a certain degree of drought stress, belonging to the stronger drought-resistant ability trees, but the water control drought tolerance ability of C. camphora was higher than that of the other 4 species and is more capable to adapt to environment of rocky desertification district.