以西洋杜鹃铁红、粉红、梅红、普红4个品种(系)的扦插苗为试验材料,分别在38℃/28℃和43℃/32℃(昼/夜)胁迫4d后转入25 ℃/22℃(昼/夜)恢复,研究不同高温对西洋杜鹃光合作用和叶绿素荧光动力学参数的影响.结果表明:高温加重了光合作用光抑制,4个品种(系)的净光合速率(Pn)都下降,气孔导度随着处理时间的延长均显著下降；胞间二氧化碳浓度随着处理时间的延长均显著升高；蒸腾速率随着处理时间的延长则表现出先升高后下降的趋势.非气孔因素是导致西洋杜鹃光合作用下降的主要因素.4个品种(系)之间对高温胁迫的反应存在差异.铁红受高温的影响相对较小,Pn在4个品种(系)中的下降幅度最小；而普红Pn的变化受高温的影响最大.在叶绿素荧光动力学参数方面,高温胁迫4d后,4个品种(系)的原初光能转换效率、光合电子传递量子效率、光化学猝灭系数和非光化学猝灭系数均显著下降.在恢复试验中,38℃组仅有少量植株存活,而43℃组则无—植株存活,表明在38和43℃胁迫下所产生的光抑制,已导致光系统Ⅱ结构在短期内受到了不可恢复的伤害或失活.%Four Rhododendron hybridwn cultivars, Tiehong, Fenhong, Meihong and Puhong, were used for the study on the effects of high temperature stress on the photosynthesis and the chlorophyll fluorescence of R. hybridwn after 4 d stress in 38℃/28℃ or 43 ℃/32 ℃( day/night) , and recovery in 25℃/22 ℃(day/night). The results were as follows: the photosynthetic rate (Pn) of the four cultivars decreased with the 38 or 43 t stress, which suggest the stress make the photoinhibition heavier. The stomatal conductance decreased and the concentration of internal leaf CO2 increased with the processing time, nonetheless, the transpiration rate fell after rising. The results suggest that nomstomatal limitations are the key factors for the decrease of Pn during the 38 and 43 t stress. The difference can be found in the response of each cultivar to the same stress, the Pn of Tiehong decreased least while that of Puhong decreased most. About the chlorophyll fluorescence, the values of higher photosystem II (PS II ) photochemical maximum efficiency, effective quantum yield of photochemical energy conversion in PS II , photochemical quenching and non-photochemical quenching decreased distinctively with the heat stresses. The results of recovery experiments, a small number of Tiehong, Puhong, and Meihong can recover after the elimination of stress, while none can recover which endured 43℃ stress, show that the heavy photoinhibitions have led to non-recoverable harm or irreversive inactivation in the structure of PS II.
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