盐桦幼树光合特性的研究

目的]为保护和开发盐桦提供依据。方法]以1年生盐桦为试验材料，研究了叶片光合参数的日变化。结果]晴天时净光合速率日变化为不对称的双峰曲线，最大值出现在上午10：00前后，为11．1773μmol／（m^2·s），第2个峰值出现在16：00～17：00，为10．1551μmol／（m^2·s）．盐桦蒸腾作用的最大值出现在16：00时前后，为7．3952μmol／（m^2·s），气孔导度与净光合速率日变化趋势相似。光合有效辐射达到1600μmol／（m^2·s）以后，盐桦幼树叶片光舍速率仍有增加：盐桦叶温与气温的日变化趋势一致，呈单峰曲线型，峰值出现在14：00，最高叶温达39℃，在11：00～13：00气孔导度与胞间CO2浓度也同步下降，15：00之后，气孔导度下降而胞间CO2浓度的上升。结论]盐桦是比较喜光的树种。

Study on Photosynthetic Characteristics of Betula halophila Young Trees

Objective] The aim was to provide the basis for the protection and development of Betula halophila.Method] With 1-year-old B.halophila as tested material,the diurnal variation of leaf photosynthetic parameter was investigated. Result] The diurnal variation of net photosynthesis rate in clear day showed as asymmetric double-peak curve.The peak value appeared at about 10 am,being 11.177 3 μmol/(m2·s),and the second peak value appeared between 16:00 and 17:00,being 10.155 1 μmol/(m2·s).The biggest value of transpiration of B. halophila appeared at about 16:00,being 7.395 2 μmol/(m2·s).Diurnal variation trend of stomatal conductance and net photosynthesis rate was similar.After the light intensity reached 1 600 μmol/(m2·s),the photosynthetic rate of Betula halophila young trees still increased.The diurnal variation trends of leaf temperature and climate temperature were uniform,which showed a single peak curve and the peak value appeared at 14:00 with highest leaf temperature of 39 ℃.During 11:00-13:00,the stomatal conductance and intercellular CO2 concn.decreased synchronously.15:00 later,the stomatal conductance decreased continuously,while intercellular CO2 concn.rose.Conclusion] B.halophila was photophilic species.