外源褪黑素对干旱胁迫下苦水玫瑰生理特性的影响

Effects of exogenous melatonin on physiological characteristics of Kushui rose under drought stress

为探明外源喷施不同浓度褪黑素(MT)对干旱胁迫下苦水玫瑰生理特性的影响,以2年生苦水玫瑰扦插苗为试材,采用盆栽控水法,设置6个处理,即正常浇水(CK1)、干旱胁迫(CK_(2)),干旱胁迫+喷施4种浓度褪黑素MT:50(T_(1))、100(T_(2))、200(T_(3))、300μmol/L(T_(4))处理,观察胁迫后叶片与枝条形态变化,测定各处理植株叶片丙二醛(MDA)含量、渗透性调节物质、相对电导率(REC)及抗氧化酶活性。结果表明,(1)干旱胁迫20 d时,与CK1相比,褪黑素(T_(1)-T_(4))处理叶片虽呈现不同程度黄化、卷曲甚至脱落,枝条也呈现不同程度下垂、干枯坏死,但表型均优于CK_(2);(2)外源喷施褪黑素(MT)可有效降低干旱胁迫下苦水玫瑰叶片丙二醛及相对电导率的升高幅度,提高过氧化物酶(POD)、超氧化物歧化酶(SOD)和过氧化氢酶(CAT)活性,促进可溶性糖(SS)、可溶性蛋白(SP)和脯氨酸(Pro)的积累,且具有明显的浓度效应。对8个指标进行多元方差分析评价,结果显示各处理对干旱胁迫的缓解效应由高到低依次为T_(3)>T_(2)=T_(4)>T_(1)>CK_(2)。其中,胁迫至20 d时,T_(3)处理下叶片MDA和REC分别较CK_(2)降低36.23%和59.97%;POD、SOD、CAT、SS、SP和Pro分别较CK_(2)提高19.16%、3.54%、45.71%、20.23%、31.42%和6.75%。综上所述,外源褪黑素通过提高抗氧化酶活性和增强生物膜稳定性来降低干旱胁迫对植株的损伤,增强抗旱性,且以200μmol/L为最适处理浓度。

In order to explore the effects of exogenous spraying of melatonin(MT)on physiological characteris⁃tics of Kushui rose under drought stress,the cutting seedlings of 2⁃year⁃old Kushui rose were examined using a pot⁃culture water⁃controlling method with 6 treatments,namely,CK_(1)(normal watering),drought stress(CK_(2))and drought stress+MT spraying with 4 concentrations of melatonin[50(T_(1)),100(T_(2)),200(T_(3)),300μmol/L(T_(4))].The morphological changes of leaves and branches were observed under each treatment.The contents of malo⁃ndialdehyde(MDA),osmotic regulatory substances(SS,SP,Pro),relative conductivity(REC)and antioxidant enzyme activities(SOD、POD、CAT)were determined.The results showed:(1)Compared with CK_(1),leaves treated with melatonin(T_(1)-T_(4))showed different degrees of chlorosis,curling and even shedding,and branches exhibited different degrees of drooping and dry necrosis at 20 d of drought stress,but these phenotypic symptoms were less se⁃verer than those treated with CK_(2);(2)Spraying melatonin(MT)effectively reduced the malondialdehyde(MDA)and relative electrical conductivity(REC),and improved the activities of peroxidase(POD),superoxide dismutase(SOD)and catalase(CAT).On the other hand,MT promoted the accumulation of soluble sugar(SS),soluble pro⁃tein(SP)and proline(Pro).However,the degree of these effect depended upon the MT concentration.Multivariate analysis of variance(ANOVA)was used to evaluate the eight indexes,whose results showed that the alleviating ef⁃fect of each treatment on drought stress was T_(3)>T_(2)=T_(4)>T_(1)>CK_(2).After 20 days of stress,MDA and REC of leaves under T_(3) treatment were 36.23%and 59.97%lower than those under CK_(2),respectively.Additionally,under T_(3) treatment,compared with CK_(2),POD,SOD,CAT,SS,SP and Pro increased by 19.16%,3.54%,45.71%,20.23%,31.42%and 6.75%,respectively.In conclusion,exogenous melatonin(MT)can reduce the damage to plants under drought stress and enhance drought resistance by improving the activity of antioxidant enzymes and en⁃hancing the stability of membrane,and 200μmol/L showed to be the optimal concentration.