盐胁迫下外源褪黑素和丛枝菌根真菌对月季幼苗生长生理特性的影响

Influence of exogenous melatonin and arbuscular mycorrhizal fungi on growth and physiological characteristics of Rosa chinensis seedling under salt stress

【目的】盐胁迫易导致月季生长发育不良、观赏品质下降,严重影响其在高盐环境或沿海地区室外绿化应用,探究施用外源褪黑素(MT)和接种丛枝菌根真菌(AMF)对其幼苗生长、叶绿素荧光参数以及激素代谢的调控作用,解析它们促进月季适应盐胁迫的生理生化机制,对于增强月季抗盐性,扩大月季应用范围具有重要意义。【方法】以月季品种‘月月红’幼苗为试验材料,采用室内盆栽试验,设置对照(CK)、100 mol/L NaCl胁迫、根际施用MT、根际接种AMF幼套近明球囊霉(Claroideoglomus etunicatum)及其组合等8个处理,考察各处理对月季幼苗生长、叶绿素荧光参数、激素代谢及抗氧化系统的影响。【结果】(1)施用MT可以促进AMF对月季幼苗根系的侵染,提高侵染率、丛枝着生率、泡囊数和侵入点数;(2)月季幼苗株高、茎粗以及生物量等在盐胁迫下显著下降,在MT或AMF处理下均不同程度增加,而AMF+MT处理下株高、茎粗无显著变化,地上部干重、地下部干重分别显著增加24.1%和37.0%;(3)月季幼苗叶绿素含量在盐胁迫下显著下降,叶绿素荧光参数也降低,MT或AMF处理能提高盐胁迫月季幼苗叶绿素含量以及叶绿素荧光参数,AMF+MT处理则使叶绿素总量、叶绿素a/b分别增加46.2%和67.2%,PSⅡ最大光化学效率(F_(v)/F_(m))、潜在活性(F_(v)/F_(o))、实际光化学效率(ΦPSⅡ)、有效光化学量子效率(Fv'/Fm')、光化学淬灭系数(qP)分别增加4.9%、51.0%、175.0%、168.7%和92.5%,而NPQ下降42.7%;(4)在盐胁迫下,月季叶片中玉米素(ZT)、赤霉素(GA)、生长素(IAA)含量下降,而脱落酸(ABA)含量增加,MT或AMF处理有利于盐胁迫下ZT、GA、IAA含量的提高以及ABA含量的下降,AMF+MT处理后ZT、GA、IAA分别增加146.9%、116.9%、35.7%,ABA下降21.1%;(5)在盐胁迫下,抗氧化酶SOD、CAT活性增强,超氧阴离子(O_(2)^(-·))产生速率和H_(2)O_(2)累积大量增加,MT或AMF处理有助于增加抗氧化酶活性并减少O_(2)^(-·)产生速率和H_(2)O_(2)含量,而AMF+MT处理能够进一步激活SOD、CAT活性,降低O_(2)^(-·)产生速率和H_(2)O_(2)累积。【结论】接种AMF、添加MT或者AMF+MT处理均可以提高盐胁迫下月季幼苗叶绿素含量,保护叶绿素荧光系统,维持植物内源激素的平衡,激活SOD、CAT等抗氧化酶活性以及降低脂质过氧化和H_(2)O_(2)累积,以减轻盐胁迫对月季幼苗的伤害,促进月季生长,并以AMF+MT处理增强月季幼苗抗盐性的效果更佳。

[Objective]Salt stress leads to poor growth and development and decreased ornamental quality of Chinese rose(Rosa chinensis Jacq.),and seriously affects their outdoor greening applications in high salt environments or coastal areas.This study explores the effects of exogenous melatonin(MT)and inoculation with arbuscular mycorrhizal fungi(AMF)on seedling growth,chlorophyll fluorescence parameters,and cytokinin metabolism,and analyzes their physiological and the biochemical mechanisms that promote rose to adapt to salt stress,in order to enhance salt resistance and expand the application of rose.[Methods]The seedling of Chinese rose variety‘Yueyue Hong’was used as experimental material to conduct indoor potting experiments.In addition,control(CK),100 mol/L NaCl stress,root administration of MT,and root inoculation of AMF larvae of the genus Claroideoglomus etatunicum and their combination were set to investigate the effects of each treatment on the growth of rose seedlings,chlorophyll fluorescence parameters,hormone metabolism,and antioxidant system.[Results](1)Application of MT promoted AMF infestation of the roots of rose seedlings and increased the infection rate,bush growth rate,number of vesicles,and invasion points.(2)Under salt stress,the growth of rose seedlings was inhibited,and plant height,stem thickness,and biomass were decreased significantly.MT and AMF treatments increased the height,stem thickness,and biomass of rose seedlings,whereas AMF+MT treatment had no significant difference in plant height and stem thickness,aboveground dry weight and underground dry weight were increased by 24.1%and 37.0%.(3)Under salt stress,the chlorophyll content of rose seedlings was decreased significantly while chlorophyll fluorescence parameters were decreased,and MT and AMF treatments could improve the chlorophyll content and chlorophyll fluorescence parameters.Under AMF+MT treatment,the total amount of chlorophyll and chlorophyll a/b was increased by 46.2%and 67.2%,respectively.PSⅡmaximum photochemical efficiency(F_(v)/F_(m)),potential activity(F_(v)/F_(o)),actual photochemical efficiency(ΦPSⅡ),effective photochemical quantum efficiency(Fv'/Fm'),and photochemical quenching coefficient(qP)were increased by 4.9%,51.0%,175.0%,168.7%,and 92.5%,respectively,whereas NPQ was decreased by 42.7%.(4)Under salt stress,zeatin(ZT),gibberellin(GA),auxin(IAA)content in leaves were decreased,whereas the abscisic acid(ABA)content was increased.MT and AMF contributed to the increase in ZT,GA,and IAA content and the decrease in ABA content.Under AMF+MT treatment,ZT,GA,and IAA content were increased by 146.9%,116.9%,35.7%,respectively,while ABA was decreased by 21.1%.(5)Under salt stress,the activity of SOD and CAT were increased,and the rate of superoxide anions(O_(2)^(-·))production and H_(2)O_(2)accumulation was increased.MT and AMF treatments decreased O_(2)^(-·)production rate and H_(2)O_(2)content,while AMF+MT treatment activated SOD and CAT activity,and reduced the rate of O_(2)^(-·)production and H_(2)O_(2)accumulation.[Conclusion]Inoculation with AMF,addition of MT,or AMF+MT treatment could increase the chlorophyll content of rose seedlings under salt stress,protect the chlorophyll fluorescence system,maintain the balance of endogenous plant hormones,activate the activity of antioxidant enzymes such as SOD and CAT,and reduce lipid peroxidation and H_(2)O_(2)accumulation,thereby reduce the damage caused by salt stress to rose seedlings,promote rose growth,and enhance the salt resistance of rose seedlings better with AMF+MT treatment.