二硫苏糖醇对海水胁迫下菠菜活性氧代谢及叶绿素荧光特性的影响

Effects of the Dithiothretiol on Activate Oxygen Metabolism and Chlorophyll Fluorescences in Spinach Leaves Under Seawater Stress

以耐海水菠菜品种‘荷兰3号’为材料,采用水培方法,研究了二硫苏糖醇(DTT)对海水胁迫及甲基紫精(MV)诱导下菠菜活性氧代谢及叶绿素荧光特性的影响。结果表明,海水胁迫与MV处理一样,诱导菠菜叶片产生氧化胁迫,使超氧阴离子( )产生速率、过氧化氢(H2O2)含量和丙二醛(MDA)含量显著上升,叶绿素a(Chl.a)、叶绿素b(Chl.b)、总叶绿素[Chl.(a+b)]和类胡萝卜素(Car.)含量显著下降,最大光量子产量(Fv/Fm)、实际光量子产量(Yield)、电子传递速率(ETR)和光化学猝灭系数(qP)显著降低,而非光化学猝灭系数(NPQ/4)显著上升;海水胁迫与MV处理下,由叶柄导入叶黄素循环活性抑制剂DTT,菠菜叶片活性氧(ROS)大量积累,导致光合色素降解加剧,Fv/Fm、Yield、ETR、NPQ、qP进一步下降。上述结果表明,海水胁迫抑制了菠菜叶片叶黄素循环活性,降低了叶片非辐射能量耗散能力,加重了叶片ROS积累,从而导致光合色素含量降低,PSⅡ活性下降,电子传递速率降低,用于光化学反应的能量部分减少,光合作用受到严重影响,说明海水胁迫下叶黄素循环在保持菠菜叶片光合色素稳定和光合作用正常运转中发挥重要作用。

The effects of the dithiothretiol （DTT） on activate oxygen metabolism and chlorophyll fluorescences under seawater stress and methyl viologen （MV）induced oxidative stress in leaves of＇Helan 3＇ （seawater tolerant cultivar） were investigated by hydroponics. The results shown that production rate of superoxide radical （O2）, content of hydrogen peroxide （H202） and malonaldehyde （MDA） were remarkably increased by seawater and MV which could induce oxidative stress on spinach leaves, whereas contents of chlorophyll a （Chl.a）, chlorophyll b （Chl.b）, total chlorophyll and carotenoid （Car.） remarkably decreased. Under the stress of seawater and treated with MV, maxmium quantum efficiency of photosystem II photochemistry （Fv/Fm）, the effectivePSII quantum yield （Yield）, apparent electron transport rate （ETR） and coefficient of photochemical quenching （qp） were decrease significantly, coefficient of nonphotochemical quenching （NPQ/4） was increased significantly. Accumulation of reactive oxygen species （ROS）, degradation of photosynthetic pigments, as well as decrease of Fv/Fm, Yield, ETR, NPQ, qe were aggravated by introduction of dithiothreitol. Our results suggested that the inhibition of xanthophyll cycle under seawater stress decreased the dissipation of non-radiative energy, enhanced the accumulation of ROS, which were leading the degradation of photosynthetic pigments, decreation of activity of PS Ⅱ and ETR, reduction of energy for photochemical reactions, and photosynthetic performances were affected significantly. Higher activity of xanthophyll cycle in seawater-tolerant spinach plays a major role in maintaining the stability of photosynthetic pigments and photosynthetic activity under seawater stress.