龙须藤净光合速率日变化及其主要影响因子

Diurnal Changes of Net Photosynthetic Rate and Influencing Environmental Factors of Bauhinia championii

采用LI-6400型便携式光合仪,对桂林岩溶石山龙须藤Bauhinia championii不同季节净光合速率Pn的日变化进行测定。结果表明,龙须藤Pn日变化曲线春季和冬季呈"单峰"型;夏季和秋季呈"双峰"型,都有明显的光合"午休"现象。夏季龙须藤Pn中午降低主要为非气孔限制,而秋季则主要为气孔限制;龙须藤夏季和秋季节有较高生长势,Pn季节变化趋势为夏季>秋季>春季>冬季;建立了Pn与其影响因子的关系模型,回归方程均达极显著水平(P<0.01)。统计分析结果显示,在春季,龙须藤Pn主要受气孔导度Gs和胞间CO2浓度Ci的影响;夏季,Pn受光合有效辐射PAR的影响较明显;秋季时,Gs是Pn主要的影响因子;而冬季则由Gs转为Ci和蒸腾速率Tr的共同作用。

Diurnal changes of net photosynthetic rate （P.） of Bauhinia championii on Guilin＇s Karst hills were measured by Li-6400 portable photosynthesis analysis system （LI-6400,Li-cor USA） in different seasons. It was found that diurnal curves of Pn were ＂single peak＂ in spring and winter, but ＂double peak＂ in summer and autumn and they were both with a significant ＂midday depression of photosynthesis＂.Pn reduction at noon in summer was mainly originated from nonstomatal limitation, while it was mainly due to stomatal limitation in autumn;Bauhinia charnpionii showed higher growth potential in summer and autumn,the seasonal changes of Pn were in the order of summer〉autumn〉spring〉winter ; The positive relationship models between Pn and its influence factors were all significant （P〈0. 01） in different seasons. Statistical analysis indicated that diurnal changes of Pn were affected by stomatal conductance （Gs） and intercellular CO2 concentration （Ci） in spring,photosynthetic active radiation （PAR） was the main factor influencing Pn in summer,the dominant factor for Pn in autumn was Gs,and Pn in winter was contributed to the the co-effects of Ci and transpiration rate （Tr）.