通过快速荧光动力学曲线探测白黄瓜光系统Ⅱ的热激胁迫效应
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国家科技攻关计划资助项目(2004BA525B14)


Heat shock stress on photosystem Ⅱ in white cucumbers probed by the fast fluoresence rise OJIP
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    摘要:

    以耐热性较强的短粗型白黄瓜和长棒型白黄瓜为试材,并以耐热性较差的‘新泰密刺’和耐热性较强的‘津春4号’为对照品种,经热激胁迫后采用植物效率仪PEA测试,进行光系统Ⅱ(PSⅡ)快速叶绿素荧光诱导动力学分析(JIP-test)及其热稳定性的热力学分析。随着热激胁迫温度的升高(在30~57 ℃下5 min),表现为PSⅡ的最大光化学效率Fv/Fm、单位面积的光合机构含有的反应中心数目RC/CSo、放氧复合体活性ρk呈“S”型下降趋势;单位反应中心以热能形式耗散的能量DIo/RC呈“S”型上升趋势。综合分析反映出热激胁迫下PSⅡ反应中心的可逆失活、放氧复合体(OEC)的钝化和热耗散的三重机制在保护PSⅡ防止光抑制中起到重要作用。热激胁迫温度超过30 ℃时ρk就开始下降;超过40 ℃时RC/CSo开始下降;超过44 ℃以上,PSⅡ热耗散能力DIo/RC才表现出增加;超过51℃时,会加重耐热性较差的新泰密刺品种PSⅡ热耗散机构对PSⅡ保护的负担。通过标准状态变性自由能变ΔGD计算的变性中点温度Tm表明,PSⅡ蛋白复合体的热稳定性优于PSⅡ反应中心复合体热的稳定性和放氧复合体(OEC)的热稳定性。对于Fv/Fm、RC/CSo、和ρk的Tm均呈现出津春4号耐热性较强,新泰密刺耐热性较差,长棒型白黄瓜和短粗型白黄瓜耐热性居中。

    Abstract:

    Fast chlorophyll fluorescence kinetics were measured by a PEA, Plant Efficiency Analyzer from Hansatech Instruments, in two strains of white cucumbers (Cucumis sativus L.) with short-fruit-type or long-fruit-type. The goal is to analyse the chlorophyll a fluorescence kinetics and the thermodynamics of photosystem Ⅱ (PSⅡ) heat shock stability of two contrast varieties of ‘XINTAIMICI’ with lower heat resistant temperature and ‘JINCHUN Ⅳ’ with a higher one. Along with increasing temperature (5 min at 30-57 ℃), the structure and function of PSⅡ shows to be more sensitive to heat shock as maximum quantum yield of primary photochemical of PSⅡ(Fv/Fm=1-Fo/Fm). The density of reaction centers (RC/CS) and the activity of the oxygen-evolving-complex activity (ρk) show a sigmoid decay, while in contrary energy dissipation per RC(DIo/RC) increases. The analysis of the data show that the determinant mechanism under the heat shock, i.e., the reversible deactivation of the PSⅡ reaction centers and of oxygen-evolving-complex (OEC) as well as the energy dissipation, plays a vital role in protecting PSⅡ to prevent photoinhibition. For heat shocks above 30 ℃ the ρk starts to decrease. Over 40℃, RC/CS begins to decrease and over 44℃, DIo/RC increases. Over 51 ℃, in ‘XINTAIMICI’ high temperature weakens the capacity of the dissipative protection mechanisms of PSⅡ.The denaturising midpoint temperature (Tm) calculated from Gibbs free energy (ΔGD ) indicates that the heat stability of protein complexes is higher than that of reaction center or that of oxygen-evolving-complex (OEC). Each midpoint temperature Tm for Fv/Fm, RC/CSo or ρk shows that the thermotolerance of ‘JINCHUN Ⅳ’ is the highest among the four cultivars. The white cucumbers with short or long fruits follow afterwards and ‘XINTAIMICI’shows the lowest heat shock resistance.

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高玉,高志奎*,张晓慧,高荣孚.通过快速荧光动力学曲线探测白黄瓜光系统Ⅱ的热激胁迫效应.生态学报,2009,29(6):3335~3341

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