外源一氧化氮供体对盐胁迫下多裂骆驼蓬幼苗光合作用和叶黄素循环的影响

Effects of Exogenous Nitric Oxide Donor on Photosynthesis and Xanthophyll Cycle of Peganum multisectum Seedlings under NaCl Stress

一氧化氮(NO)是植物体内新发现的一种活性分子。为了探讨外源NO对盐胁迫下荒漠植物光合生理响应的调节作用,以多裂骆驼蓬为试验材料,研究叶面喷施NO供体硝普钠(SNP)预处理对根施NaCl胁迫下叶片光合色素含量、气体交换参数、叶绿体Hill反应活力和ATPase活性、叶绿素荧光参数及叶黄素循环的影响。结果表明:①0.15 mmol.L-1SNP可显著缓解300 mmol.L-1NaCl胁迫下叶绿素a、b和类胡萝卜素含量及净光合速率(Pn)、气孔导度(Gs)、蒸腾速率(Tr)和气孔限制值(Ls)的下降和细胞间隙CO2浓度(Ci)的升高;②SNP处理减小了NaCl胁迫诱导的叶绿体Hill反应活力和Ca2+-ATPase、Mg2+-ATPase活性的下降幅度;③NaCl胁迫下叶绿体最大荧光(Fm)、PSⅡ潜在光化学效率(Fv/F0)、最大光化学效率(Fv/Fm)、实际光化学效率(ΦPSⅡ)和光化学猝灭系数(qP)显著降低,天线热耗散(D)略微下降,初始荧光(F0)和非光化学猝灭系数(NPQ)明显提高。SNP处理使NaCl胁迫下的F0显著降低,Fm、Fv/F0、Fv/Fm、ΦPSⅡ、qP、NPQ和D明显提高;④NaCl胁迫引起叶黄素循环库(V+A+Z)显著降低和脱环氧化状态(A+Z)/(V+A+Z)明显提高,SNP处理使NaCl胁迫下的V+A+Z明显提高,(A+Z)/(V+A+Z)显著下降。由此表明,NO能够缓解盐胁迫下非气孔因素引起的光合速率的下降及光抑制对光合系统的破坏作用,而非光化学效率的提高和天线热耗散的增强可能是NO保护光合系统并提高光合速率的重要机制之一。

Nitric oxide（NO） is an active molecule involved in many biological pathways.To investigate the photosynthetic and physiological responses of desert plants under salt stress to exogenous NO,we examined the effects of spraying NO with the donor of sodium nitroprusside（SNP） on the photosynthetic pigment content,gas exchange,activities of Hill reaction and ATPase of chloroplast,chlorophyll fluorescence and xanthophyll cycle in leaves of Peganum multisectum Bobr seedlings.The results are as follows.（1） By pretreatment with 0.15 mmol·L^-1SNP,the decreases of chl.a,chl.b and carotenoid contents,the net photosynthetic rate（Pn）,stomatal conductance（Gs）,transpiration rate（Tr） and stomatal limitation value（Ls） and the increase of intercellular CO2 concentration（Ci） are significantly alleviated at the stress condition of 300 mmol·L^-1 NaCl.（2） SNP pretreatment alleviates the decreases of activities of Hill reaction and Ca^2＋-ATPase,Mg^2＋-ATPase in chloroplast by NaCl stress.（3） Under NaCl stress,the maximum fluorescence（Fm）,potential photochemical efficiency（Fv/F0）,maximum photochemical efficiency（Fv/Fm）,actual PSII efficiency（ΦPSⅡ）,photochemical quenching（qP） are significantly decreased,and antennae heat dissipation（D） is slightly decreased.But initial fluorescence（F0） and non-photochemical quenching（NPQ） are significantly increased.After pretreated with SNP,F0 is evidently decreased,while Fm,Fv/F0,Fv/Fm,ΦPSⅡ,qP,NPQ and D are significantly increased under NaCl stress.（4） Under NaCl stress,the xanthophyll cycle pool（V＋A＋Z） is evidently decreased,but（A＋Z）/（V＋A＋Z）（the de-epoxidation extent of xanthophyll cycle） is significantly increased.After pretreated with SNP,V＋A＋Z increased,but（A＋Z）/（V＋A＋Z） significantly decreases under NaCl stress.In conclusion,NO can alleviate the decrease of photosynthetic rate induced by non-stomata factors and the damage of photoinhibition on photosynthetic system,and increasing of non-photochemical efficiency and antennae heat dissipation is probably the mechanism that NO protects photosynthetic system and improves photosynthetic ability under salt stress.