干旱胁迫对苜蓿幼苗叶绿素荧光特性和膜脂过氧化的影响

Effects of drought stress on chlorophyll fluorescenceparameters and lipid peroxodation inalfalfa seedling

摘要:

为明确干旱胁迫对紫花苜蓿不同抗旱品种幼苗叶片的光合生理及膜脂过氧化的影响,以陇中苜蓿(强抗旱),陇东苜蓿(中抗旱)和甘农3号紫花苜蓿(弱抗旱)为试验材料,采用营养液砂培方法,以-1.2 MPa PEG-6000溶液模拟干旱胁迫,比较不同胁迫时间(0、3、6、9和12 d)处理下紫花苜蓿叶片相对含水量(RWC)、叶绿素(Chl)含量、活性氧(O2·-、H2O2 和OH· )和丙二醛(MDA)含量及叶绿素荧光参数的变化。结果表明:随干旱胁迫时间延长,供试苜蓿品种的RWC、Chl a 含量、Chl a/b 比值、最大荧光(Fm)、潜在光化学效率(Fv/Fo)、最大光化学效率(Fv/Fm)、光化学淬灭系数(qP )、PSⅡ光化学量子产量(Yield)和表观光合电子传递速率(ETR)不断下降;而其O2·-、H2O2、OH· 和MDA 含量不断增加。陇中苜蓿叶片RWC、Chl a 含量、Fm、Fv/Fo、Fv/Fm、Yield 和ETR 的降幅及H2O2 和MDA含量的增幅均低于陇东苜蓿和甘农3号。相关性分析表明,供试苜蓿RWC、Chl a、Chl a/b、Fm、Fv/Fm、qP 、ETR、Yield 与O2·-、H2O2、OH· 、MDA 均呈极显著负相关。主成分分析表明,对陇中苜蓿抗旱性影响最大的主要为叶绿素荧光特性因子(qN 、Yield、Chl a、qP 和ETR),而对陇东苜蓿和甘农3号抗旱性影响最大的主要为膜脂过氧化因子(OH· 、H2O2、O2·-和MDA)。相比陇东苜蓿和甘农3号,陇中苜蓿的叶绿素荧光参数受干旱影响小,其抗旱的重要生理原因是具有较强的叶片保水能力,较低的光合机构损伤及膜脂过氧化程度。

Abstract:

The effects of drought stress on photosynthetic physiology and lipid peroxidation in leaf of differentdrought-tolerant alfalfa (Medicago sativa) varieties,including Longzhong (strong drought-tolerant),Longdong(moderate drought-tolerant) and Gannong No.3 (drought-sensitive),were studied through sand cultureexperiment in glasshouse.The changes of relative water content (RWC),chlorophyll content,the levels of reactiveoxygen species (O2·- ,H2O2 and OH· ) and malondialdehyde (MDA),and chlorophyll fluorescence parameterswere measured under drought stress stimulated by polyethylene glycol (PEG-6000) with the water potentialof -1.2 MPa at 0,3,6,9 and 12 days of treatment.The results showed that,with the prolonging of stresstime,RWC,chlorophyll a content,chlorophyll a/b ratio,maximum fluorescence (Fm),potential photochemicalefficiency (Fv/Fo),maximal chemical efficiency (Fv/Fm),photochemical quenching (qP),photochemical quantumyield of photosystem Ⅱ (Yield) and photosynthetic electron transport rate (ETR) in leaf of tested varietiesdecreased gradually,while the levels of O2·- ,H2O2,OH· and MDA increased continuously.However,theincrease amplitudes of H2O2 and MDA and the decrease amplitudes of RWC,chlorophyll a content,Fm,Fv/Fo,Fv/Fm,Yield and ETR in leaf of Longzhong were lower than those of Longdong and Gannong No.3.Simplecorrelation analysis showed that there were significant negative correlation between RWC,Chl a,Chl a/b,Fm,Fv/Fm,qP ,ETR,Yield and O2·- ,H2O2,OH· ,MDA.Principal component analysis indicated that chlorophyllfluorescence characteristic factor (including qN,Yield,Chl a,qP and ETR) was responsive for the drought-toleranceof Longzhong,while the drought-tolerance of Longdong and Gannong No.3 were mainly affected bymembrane lipid peroxidation factor (including OH· ,H2O2,O2·- and MDA).Overall,the variations in chlorophyllfluorescence parameters of Longzhong were less affected by drought stress than those in Longdong andGannong No.3.The stronger water retention capacity and lower degrees of photosynthetic apparatus damageand lipid peroxidation might contribute to the greater drought-tolerance of Longzhong.