低温对南极假山毛榉光系统Ⅱ的影响

  目的  探究低温对南极假山毛榉Nothofagus antarctica光系统Ⅱ(PSⅡ)的影响，利用综合生物反应指数(IBR)评价法计算低温胁迫下的叶绿素荧光综合指标的可行性。  方法  采取逐步降低环境温度的方法(从25 ℃降至?25 ℃)，测量并分析南极假山毛榉叶片的相对叶绿素含量和快速叶绿素荧光，计算各温度下植株的综合生物反应指数，综合评价温度降低对PSⅡ光化学活性的影响。  结果  环境温度为15 ℃时，PSⅡ光化学活性无变化；环境温度为5 ℃时，放氧复合体损伤，PSⅡ各单位之间的能量流通受阻。低温(?5、?15和?25 ℃)导致相对叶绿素含量显著降低，PSⅡ供体侧受损加剧，电子传递效率下降，PSⅡ各单位之间的能量流通混乱，热耗散显著增加。各温度处理下植株的综合生物反应指数和相对叶绿素含量与测试温度均表现为显著负相关。  结论  低于?5 ℃的低温会对南极假山毛榉PSⅡ的光化学活性造成严重胁迫，综合生物反应指数可以综合评价低温胁迫对植株PSⅡ光化学活性和相对叶绿素含量的影响。图7表1参24

Effect of low temperature on photosystem Ⅱ in Nothofagus antarctica

  Objective  Nothofagus antarctica PSⅡ photochemical performance under low temperature was assessed and its results were used in calculation integrated biomarker response (IBR) to assess the synthetical indicator of chlorophyll fluorescence under low temperature stress.  Method  The environment temperature of N. antarctica was changed gradually (from 25 ℃ to ?25 ℃). After exposed, relative chlorophyll content (SPAD value) and fast chlorophyll fluorescence were measured and analysed, IBR were calculated, to assess the effect of low temperature PSⅡ photochemical activity.  Result  15 ℃ hardly affects the PSⅡ photochemical activity. Oxygen-evolving complex and energy flow between PSⅡ units were disturbed under ?5 ℃. Under the low temperature of ?5, ?15 and ?25 ℃, SPAD value was remarkably reduced, and the PSⅡ donor side, electron transport of PSⅡ, energy flow between PSⅡunits were all disturbed seriously; heat dissipation was remarkably increased. IBR under different temperature treatments have a significant negative correlation with SPAD value and temperature.  Conclusion  The damage of PSⅡ photochemical activity by low temperature (below ?5 ℃) was serious, and IBR can be used as a comprehensive parameter to evaluate the effect of low temperatures on PSⅡ photochemical activity and SPAD value. Ch, 7 fig. 1 tab. 24 ref.]