冰冻对珊瑚树(Viburnum odoratissimum)叶片光合效率的影响

光合作用的冰冻伤害研究大多利用离体叶片、原生质体,甚至叶绿体类囊体进行人工冰冻预处理,关于室外自然温度下出现的植物光合作用冰冻伤害,特别是冰冻影响光合量子效率的研究报告还很少。虽然光合碳同化受抑是最早可以测到的冰冻伤害征状,但其机理迄今不清楚(Krause等1982,Krause和Klosson1983)。

The Effect of Freezing Injury on the Photosynthetic Efficiency in Sweet Viburnum (Viburnum odoratissimum) Leaves

Studies on effects of freezing temperatures on photosynthesis in sweet viburnum (Viburnum odoratissimum) leaves were carried out after natural or artificial freezing pretreatment. Photosynthetic rate, stomatal conductance, RuBP carboxylation efficiency, RuBP regenera- tion capacity, ATP content and fluorescence yield as well as electric resistance of leaves sub- jected to freezing temperatures decreased, whe- reas intercellular CO_2 concentration and apparent photosynthetic quantum requirement increased. In the meantime marked changes in cellular ultrastructure such as plasmolysis,. swelling, unstacking of grana and increase of plastoglobuli were observed in chloroplasts of leaves subjected to freezing temperatures. The results indicate that the primary cause of in- hibition of photosynthesis by freezing injury is the decrease in activities of photosynthetic energy-transducing system and carbon assimi lating enzyme system rather than stomatal closure. The ultrastructural injury caused by freezing temperatures is responsible for the decrease in the photosynthetic activities of mesophyll cells.