24-表油菜素内酯对干旱胁迫下辣椒叶片快速叶绿素荧光诱导动力学曲线的影响

Effects of 24-Epibrassinolide on the Chlorophyll Fluorescence Transient in Leaves of Pepper under Drought Stress

以辣椒品种“超辣九号”为试材,采用15%的PEG6000模拟干旱,研究了0.1μmol·L^-1外源24-表油菜素内酯(EBR)处理对干旱胁迫下辣椒叶片快速叶绿素荧光诱导动力学曲线(OJIP)的影响。结果表明:干旱胁迫降低了辣椒叶片的光化学效率和光合性能,导致干旱光抑制的发生。干旱胁迫既损伤了辣椒叶片PSⅡ供体侧放氧复合体(OEC),同时也对PSⅡ反应中心和受体侧造成伤害,阻碍了光合电子传递;干旱胁迫还导致单位叶面积有活性反应中心数目(RC/CS)的下降,并降低了单位叶面积吸收的光能(ABS/CS)、捕获的光能(TRo/CS)和进行电子传递的能量(ETo/CS),同时诱导了单位叶面积热耗散(DIo/CS)的增加。这说明辣椒遭受干旱胁迫后启动了相应的防御机制,一方面通过PSⅡ的可逆失活减少光能吸收与传递,另一方面通过促进热耗散减少过剩激发能的积累。EBR处理改善了干旱胁迫下辣椒叶片PSⅡ受体侧的电子传递,缓解了单位叶面积有活性反应中心数目的减少,优化了光合电子传递的进行,并维持相对较高的热耗散能力,从而减轻了干旱光抑制程度,对干旱胁迫下辣椒叶片光合机构和光合性能起到保护作用。

In order to investigate the role of exogenous 24-epibrassinolide(EBR)in improving drought tolerance in pepper(Capsicum annuum L.cv.Chaola 9),the chlorophyll fluorescence transient curve(OJIP)was examined in plants under drought stress(15%PEG6000).Drought reduced the photochemical efficiency and photosynthetic performance of pepper leaves,and induced photoinhibition.Drought not only disrupted the oxygen-evolving complex(OEC),but also impaired the PSⅡreaction and acceptor side of PSⅡ,which inhibited the photosynthetic electron transportation.Drought decreased the number of active PSⅡreaction centers per unit area.Drought also decreased the specific energy fluxes per unit area for absorption(ABS/CS),trapping(TRo/CS),electron transport(ETo/RC),but increased dissipation energy fluxes per unit area(DIo/CS).These results indicated that drought initiated defense mechanism by decreasing the absorption and transportation of light energy by reversible deactiveation of PSⅡ,and reducing the accumulation of excess excitation energy by promoting heat dissipation.EBR treatment improved the electron transport of PSⅡacceptor side,alleviated the drought-induced decrease of active reaction center per unit area,optimized the process of photosynthetic electron transport,maintained high heat dissipation capacity in pepper leaves under drought,and alleviated drought-induced photoinhibition.In conclusion,EBR could optimize photochemical efficiency and photosynthetic performance,and protect the photosynthetic electron transport chain and PSⅡreaction center in pepper leaves under drought stress.