外源一氧化氮供体对镉胁迫下黑麦草幼苗活性氧代谢、光合作用和叶黄素循环的影响

Effects of an exogenous nitric oxide donor on active oxygen metabolism,photosynthesis and the xanthophyll cycle in Ryegrass(Lolium perenne L.) seedlings under cadmium stress

为了探讨外源NO对镉胁迫下牧草生理响应的调节作用,采用溶液培养方法,以多年生黑麦草为试验材料,研究了外源NO供体硝普钠(SNP)对镉胁迫下黑麦草幼苗生长、活性氧代谢、光合作用和叶黄素循环的影响.结果表明,150μmol·L-1SNP能明显缓解100mg·L-1Cd2+对黑麦草幼苗生长的抑制作用,提高幼苗的生长速度.与单纯镉胁迫相比,外源150μmol·L-1SNP显著抑制镉胁迫下黑麦草幼苗根系和叶片超氧化物歧化酶(SOD)、抗坏血酸过氧化物酶(APX)活性的下降和过氧化物酶(POD)活性的升高,促进过氧化氢酶(CAT)活性和谷胱甘肽(GSH)含量的提高,降低抗坏血酸(ASA)、H2O2和丙二醛(MDA)含量及超氧阴离子(O·2-)产生速率.同时,外源SNP处理不仅降低了镉胁迫下黑麦草叶片净光合速率(Pn)、气孔导度(Gs)、蒸腾速率(Tr)、叶绿素最大荧光(Fm)、PSII原初光能转换效率(Fv/Fm)、光合电子传递量子效率(ΦPSII)、光化学荧光猝灭系数(qP)、光合电子传递速率(ETR)和光化学速率(PCR)的下降及初始荧光(F0)的上升幅度,还提高了非光化学荧光猝灭系数(NPQ)和叶绿素含量及叶黄素循环库(V+A+Z)的大小,使叶黄素循环脱环氧化状态(A+Z)/(V+A+Z)升高.由此表明,外源NO可通过提高活性氧清除能力和增强依赖于叶黄素循环的非辐射能量耗散,保护由镉胁迫引起的黑麦草幼苗叶片光合机构的破坏,从而提高光合效率.

To understand the regulating effect of exogenous nitric oxide on the physiological response of herbage under cadmium stress, we have examined the effects of exogenous nitric oxide with the donor Sodium Nitroprusside （SNP） on the growth, metabolism of reactive oxygen species, photosynthesis, and xanthophyll cycle in the perennial ryegrass （Lolium perenne L. ）. Hydroponic experiments showed that addition of 150 μmol· L^-1 exogenous SNP significantly alleviates the inhibitory effect of 100 mg·L^-1 Cd^2＋ stress on the growth of ryegrass seedlings in the following aspects： （ 1 ） inhibits the decrease of the activities of Superoxide Dismutase （SOD） and Ascorbate Peroxidase （APX） ; （2） inhibits the increase of peroxidase （POD） activity in roots and leaves of ryegrass seedlings; （3） promotes the increase of catalase （CAT） activity and glutathione （GSH） content; （4） decreases the contents of Ascorbic Acid （ ASA ） , H2O2 , and malondiadehyde （ MDA ） and production rate of O2^.- . Exogenous SNP also inhibits the decreases of net photosynthetic rate （Pn）, stomatal conductance （Gs）, transpiration rate （Tr）, maximum fluorescence （Fm ）, PSII intrinsic photochemical efficiency （Fv/Fm ） , quantum yield of PSII （ФPSII） , photochemical quenching （qv）, electron transport rate （ ETR）, and photochemical rate （PCR） and the increase of minimal fluorescence （ Fo） ; and also inhibits the increase of Non-Photochemical Quenching （NPQ） , chlorophyll content, xanthophyll cycle pool size and the de-epoxidation extent of the xanthophyll cycle （A ＋ Z）/（ V ＋ A ＋ Z）. These resuhs suggest that exogenous NO protects against damage of the leaf photosynthetic apparatus of ryegrass seedlings under Cadmium stress by promoting reactive oxygen scavenging and non-radiative energy dissipation through the xanthophyll cycle, thus elevating the photosynthetic efficiency.