模拟干旱胁迫对高山杜鹃光合生理特性的影响

摘要

以不同浓度（5%～25%）的PEG-6000模拟干旱胁迫处理高山杜鹃幼苗,研究了不同程度干旱胁迫下高山杜鹃叶片光合生理特性的变化。结果表明,干旱胁迫对高山杜鹃幼苗叶片光合和荧光参数的影响与其抗旱性密切相关,其中净光合速率（Pn）与气孔导度（Gs）的相关系数较大（r=0.988 1,n=5）。随着干旱胁迫程度加重,在高山杜鹃叶片各种光合色素含量均比对照有不同程度增加的同时,叶片的Pn、Gs、蒸腾速率（Tr）、PSⅡ最大光化学效率（Fv/Fm）、实际光化学效率（Fv′/Fm′）以及光化学猝灭系数（qP）均下降,这表明在高浓度的PEG-6000干旱胁迫下叶绿体片层中捕光Chla/b-Pro复合体已经受到损伤,光合机构受到严重破坏,明显抵消了叶片总叶绿素浓缩的综合作用。综合多个指标,分析得出：在干旱胁迫下高山杜鹃叶片净光合速率的降低主要是由非气孔因素引起的。%By adding different concentrations（5% to 25%） of polyethylene glycol（PEG-6000） into Hogaland solution to simulate the drought stress,the change of photosynthetic physiological characteristics in leaves of Rhododendron hybrides ‘Cosmopolitan’ was investigated.The results show that there is a close correlation between drought-resistance and the alteration of photosynthetic characters and chlorophyll fluorescence parameters,of which the correlation index of the net photosynthesis rate（Pn） and stomatal conductance（Gs） is higher（r=0.988 1,n=5）.With increasing drought stress,the content of photosynthetic pigments increases,while Pn,Gs,transpiration rate（Tr）,the maximal photochemical efficiency of PSⅡ（Fv/Fm）,actual photochemical efficiency of PSⅡ（Fv′/Fm′） and photochemical quenching coefficient（qP） decreases,which demonstrates that light-harvesting chlorophyll a/b proteins in the lamella of chloroplasts are destroyed,the structures of photosystem are damaged seriously and the advantage of inspissation of photosynthetic pigments is neutralized.The comprehensive results indicate that the reduction of Pn under drought stress is mainly due to non-stomatal limitation.