热激胁迫对番茄果实表面光系统活性的影响

Effects of Heat Shock Stress on the Photosystem Activity of Tomato Fruit Surface

以‘保罗塔’番茄果实为试材,采用叶绿素成像荧光仪（MINI-IMAGING-PAM）和QE65000光谱议测试分析了热激胁迫对番茄果实表面光化学活性和叶绿素荧光光谱的影响。结果表明：在较低的热激胁迫下（36-43℃）,最大光化学量子产量Fv/Fm稳中有降,反映温度胁迫引起PSⅡ功能的部分抑制,而此时调节性能量耗散量子产量Y（NPQ）的增加耗散了过剩光能,以减轻过剩光能对光合机构的进一步伤害;当温度超过43℃时,非调节性能量耗散的量子产量Y（NO）显著增加,Fv/Fm、PSⅡ天线转化效率Fv′/Fm′和电子传递ETR急剧下降,Y（NPQ）开始下降,表明PSⅡ反应中心的天线色素耗散机制可能遭到破坏,对高温胁迫的自我调节功能开始下降,PSⅡ反应中心已开始失活,光抑制程度加重;当温度超过果实表面PSⅡ蛋白复合体变性中点温度51.4℃时,激发能分配不平衡偏离系数（β/α–1）显著上升,叶绿素荧光衰减率Rfd急剧下降,反映此时激发能分配严重失衡,番茄潜在的CO2同化能力极弱。通过对标准状态变性自由能变△GD计算的变性中点温度Tm得出,Tm（Fv/Fm）大于Tm[Y（II）],说明PSⅡ的耐热性稍强于整个光合作用。

The effect of heat shock stress on the photochemical activity and chlorophyll fluorescence spectra of tomato fruit surface was studied by a MINI-IMAGING-PAM system and QE65000 spectrometer.The results showed that the maximal photochemical efficiency（Fv/Fm）decreased steadliy under lower temperatue of heat shock stress（36-43 ℃）,which indicated that the PSⅡ could be ihhibited partly under temperature stress,and at this point,the increased Y（NPQ）dissipated the surplus energy so as to alleviate further damage to photosynthetic apparatus.When the temperature exceeded 43 ℃,the quantum yield of nonregulated energy dissipation Y（NO）increased significantly,Fv/Fm,the open PSⅡ reaction centers（Fv′/Fm′）and the apparent electron transport rate（ETR）decreased sharply,and Y（NPQ）began to decrease,indicating that antenna pigment dissipation mechanism of PSⅡ reaction center might have been damaged,and consequently the self-adjustment function of high-temperature stress began to decrease.Meantime,PSⅡ reaction center turned inactive and the photoinhibition was aggravated.When the temperature exceeded the enaturalization midpoint temperature（Tm（Fv/Fm）,51.4 ℃）,the relative deviation（β/α-1）from full balance between two photosystems increased,while the fluorescence decline ratio（Rfd）decreased sharply,showing that the excitation energy distribution was seriously imbalanced and the assimilation capacity of CO2 was extremely weak.Tm（Fv/Fm） calculated from Gibbs free energ（△GD）was higher than Tm[Y（II）],indicating that the heat resistance of PSⅡ was a little stronger than that of the whole photosynthesis.