夜间低温对2种桉树幼苗光合特性的影响

Effects of Nocturnal Low Temperature on Photosynthetic Characteristics of Eucalyptus urophylla and E.dunnii

以人工气候箱模拟夜间低温处理尾叶桉和邓恩桉幼苗,研究其对2种桉树的光合特性和叶绿体超微结构的影响.结果表明:夜间低温使尾叶桉和邓恩桉的净光合速率、气孔导度和蒸腾速率均降低;胞间CO2浓度和气孔限制值升高;2种桉树幼苗的水分利用率变化有一定的差异,邓恩桉的水分利用率随低温胁迫升高,而尾叶桉的水分利用率则先升高然后下降;同时,低温胁迫下尾叶桉和邓恩桉气孔导度与净光合速率和蒸腾速率均呈明显的线性关系.夜间低温导致2种桉树叶绿体肿胀变形,淀粉粒降解,对尾叶桉的影响要比邓恩桉的影响大.

With nocturnal low temperature treatments for 12 h each day, the chloroplast ultrastructures were observed and net photosynthetic rate （Pn）, stomata conductance （Gs）, intercellular CO2 concentration （Ci） ,stomata limitation （Ls）,transpiration rate （Tr） and water use efficiency （WUE） of Eucalyptus urophylla and E. dunnii seedling leaves were measured. The results showed that Pn,Gs and Tr of E. urophylla and E. dunnii seedling leaves were significantly inhibited by nocturnal low temperature treatments but Ci and Ls increased. There were some differences in the change of WUE between two eucalypts species. The WUE of E. dunnii increased always,while the WUE of E. urophylla increased first and then decreased. At the same time,a linear relationship existed between Pn and Gs and between Tr and Gs respectively. The shape of chloroplasts changed gradually from fusiform to round and starch grains decomposed slightly.