不同土壤水分条件下麻栎盆栽实生苗的光合响应

在南京林业大学树木园内,应用Li-6400光合作用测定系统测定一年生麻栎（Quercus acutissima Carruth）盆栽实生苗在不同土壤水分条件下的光合响应参数、相同光合有效辐射强度下的净光合作用参数、高光强度下的Pn-CO2变化曲线;用光合作用光响应实测值和直角双曲线修正模型对不同土壤水分条件下麻栎的光响应曲线进行拟合,探讨双曲线修正模型对麻栎幼苗的适用性及麻栎的光合响应规律.结果表明：1）在光合有效辐射强度160μmol/（m2·s）条件下,土壤含水量为24.0％、14.5％、11.4％的处理组和土壤含水量32.0％的对照组之间的净光合速率及蒸腾速率存在显著性差异（P＜0.05）;2）直角双曲线修正模型拟合出的光响应数据除了光饱和点和实测值有较大的差异外,拟合的其他光响应数据相差不大,并随土壤含水量的变化和实测值呈现相同的趋势;3）麻栎的羧化效率、CO2补偿点都随土壤含水量的降低而降低,土壤含水量抑制了1,5-二磷酸核酮糖羧化酶（Rubisco）的酶活性.

Photosynthetic response of potted Quercus acutissima Carruth seedlings under different soil moisture conditions

Photosynthesis-light response curve,photosynthesis-CO2 response curve and parameters of photosynthesis in leaves of potted Quercus acutissima Carruth seedlings under different soil moisture conditions were measured with Li-cor-6400 portable photosynthesis system in the arboretum of Nanjing Forestry University.The photosynthesis-light response curves were fitted and analyzed by actual measurement and a modified model based on the rectangular hyperbola model.The results were as follows.1） When the photosynthetically active radiation intensity was 160 μmol/（m2· s）,the net photosynthesis rate and transpiration rate of seedlings grown at soil moisture contents of 24％,14.5％ and 11.4％ were significantly different with those of seedlings grown at a soil moisture content of 32％.2） The modified rectangular hyperbola model could well fit parameters of photosynthesis-light response of leaves in Q.acutissima Carruth of all treatments except light saturation point,which had an evident difference between simulated value and measured value.The trend of photosynthesis-light response curve of leaves in Q.acutissima Carruth of all treatments was same as that of actual measurement.3） Both carboxylation efficiency and CO2 compensation point of Q.acutissima Carruth decreased with the reduction of soil moisture,so it is concluded that water stress inhibits Rubisco＇ s activity.