遮阴条件下大叶竹节树光合特性和荧光参数的变化

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

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.

To study the adaptability of Carallia garciniaefoliato 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/Fmand Fv/Foin the shading treatments were significantly higher than under full day light and increased with increasing shading,indicating that C.garciniaefoliais 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/Fmand Fv/Fovalues increased,thus improving its adaptability to shading conditions.