遮阴条件下大叶竹节树光合特性和荧光参数的变化

为研究大叶竹节树对弱光的适应性,通过盆栽实验,分析了不同程度(0%,25%,50%,75%)遮阴条件下大叶竹节树幼苗光合特性和荧光参数的变化.结果表明,随着遮阴程度增加,叶片净光合速率(Pn)、气孔导度(Gs)、蒸腾速率(Tr)、水分利用效率(WUE)和光合有效辐射(PAR)随之减小,而胞间CO2浓度(Ci)随之增大,说明非气孔制限因素是大叶竹节树光合速率下降的主要原因.各遮阴条件下叶片总叶绿素(a+b)、叶绿素a和叶绿素b质量比均显著高于全光照,且随遮阴程度的增加叶绿素质量比逐渐上升,而叶绿素a/b值则随着遮阴程度的增强而下降.叶绿素荧光参数PSⅡ原初光能转化效率(Fv/Fm)和潜在活性(Fv/Fo)的日变化呈单谷曲线;各遮阴条件下Fv/Fm和Fv/Fo值均高于全光照,且与遮阴程度正相关,说明大叶竹节树是一种耐荫性很强的植物.在遮阴条件下,光补偿点、光饱和点、净光合速率、暗呼吸速率和叶绿素a/b值降低,而叶绿素a和b质量比、光能利用率、Fv/Fm以及Fv/Fo值提高,从而增强弱光条件下的生长能力.

Effects of Shading on the Photosynthetic Characteristics and Chlorophyll Fluorescence Parameters of Carallia garciniaefolia

To study the adaptability of Carallia garciniaefolia to low light conditions, the effects of different shading treatments (25%, 50% and 75% shading) on the photosynthetic characteristics and chlorophyll fluorescence of C. garciniaefolia seedlings were studied in a pot experiment. The results showed that net photosynthetic rate (Pn), stomatal conductivity (Gs), transpiration rate (Tr), water use efficiency (WUE) and photosynthetic active radiation (PAR) of the plant decreased, while its stomatal CO2 concentration (Ci) increased significantly with increasing shading, suggesting that non-stomatal limitation is the main cause of the reduction in photosynthesis rate of C. garciniaefolia. The contents of total chlorophyll (a+b), chlorophyll a and chlorophyll b in the leaves of the plants grown under different shading conditions were all significantly higher than under full day light, and increased with increasing shading, while chlorophyll a/b decreased. Fv/Fm and Fv/Fo in the shading treatments were significantly higher than under full day light and increased with increasing shading, indicating that C. garciniaefolia is a strongly shade-tolerant plant. Under the shading conditions, the light saturation point, light compensation point and chlorophyll a/b of C. garciniaefolia decreased, but he contents of its total chlorophyll, chlorophyll a and chlorophyll b, and the Fv/Fm and Fv/Fo values increased, thus improving its adaptability to shading conditions.