外源CaCl_(2)对盐胁迫下苹果砧木T337生理特性的影响

Effect of Exogenous CaCl_(2) on Physiological Characteristics of Apple Rootstock T337 under Salt Stress

为探究不同浓度外源喷施CaCl_(2)对盐胁迫下苹果幼苗生理特性的影响,以二年生T337实生苗为试材,通过盆栽试验法,设置100 mmol/L NaCl(T1)和100 mmol/L NaCl+4种不同浓度CaCl_(2)(5.0(T2),7.5(T3),10.0(T4),12.5 mmol/L(T5))处理,以去离子水浇灌为对照(CK)。测定各处理组的叶绿素含量、光合与荧光参数、抗氧化酶活性及渗透调节物质含量,并对其进行相关性和主成分分析。结果表明,随胁迫时间延长,T337叶片的过氧化氢酶(CAT)、过氧化物酶(POD)、超氧化物歧化酶(SOD)呈先升后降趋势,丙二醛(MDA)、胞间CO_(2)浓度(Ci)、脯氨酸(Pro)和相对电导率(REC)呈不断上升趋势,初始荧光(F0)、PSⅡ最大光能转化率(Fv/Fm)、气孔导度(Gs)和蒸腾速率(Tr)呈下降趋势;相比CK和T1,外源CaCl_(2)处理后T337叶片各指标的变幅均减小,存在明显浓度效应。其中,T4(10 mmol/L)处理下相对叶绿素含量(SPAD)、Pn、Tr、POD、F0及SOD降幅最小,显著高于其他处理组;MDA、REC和Ci升幅最小,显著高于CK,低于其他处理组。14个指标相关性分析表明,Pn与CAT、Tr、Gs、F0、Fv/Fm、ETR、SPAD、SOD和POD呈正相关,与Pro、MDA、Ci、REC呈负相关。将盐胁迫处理后相关的14个指标进行主成分分析,提取特征值大于1的2个主成分,其特征值分别为11.190,2.295;第一、二主成分方差贡献率依次为79.930%,16.394%,累计方差贡献率达到96.324%,符合分析要求。依据主成分得分排序,外源CaCl_(2)对T337盐胁迫缓解能力由高到低为T4>T3>T2>T5。因此,10 mmol/L的CaCl_(2)能更好地改善盐胁迫下T337砧木叶片的光合荧光特性、提高抗氧化酶系统和渗透调节能力、增强生物膜稳定性和通透性达到缓解盐胁迫的效应。

To explore the effects of spraying CaCl_(2) at different concentrations on physiological characteristics of apple seedlings under salt stress,two-year-old T337 seedlings were used as test materials,and the pot experiment was used to set 100 mmol/L NaCl(T1)and 100 mmol/L NaCl+four different concentrations of CaCl_(2)(5.0(T2),7.5(T3),10.0(T4),12.5 mmol/L(T5))treatment,watering with deionized water was used as the control(CK).Determine the chlorophyll content,photosynthetic and fluorescence parameters,antioxidant enzyme activity and osmotic adjustment substance content of each treatment group,and carry out correlation and principal component analysis.The results showed that with prolonged stress time,the catalase(CAT),peroxidase(POD),superoxide dismutase(SOD)of T337 leaves first increased and then decreased,malondialdehyde(MDA),intercellular CO_(2) concentration(Ci),proline(Pro)and relative conductivity(REC)showed a rising trend,initial fluorescence(F0),PSⅡmaximum light energy conversion rate(Fv/Fm)stomatal conductance(Gs)and the transpiration rate(Tr)showed a downward trend;compared with CK and T1,the variation amplitudes of T337 leaves after treatment with exogenous CaCl_(2) were all reduced,and there was a significant concentration effect.Among them,the relative chlorophyll content(SPAD),Pn,Tr,POD,F0 and SOD decreased the least under T4(10mmol/L)treatment,which was significantly higher than other treatment groups;MDA,REC and Ci increased the least,which was significantly higher than CK and lower than others processing group.Correlation analysis of 14 indicators showed that Pn was positively correlated with CAT,Tr,Gs,F0,Fv/Fm,ETR,SPAD,SOD and POD,and negatively correlated with Pro,MDA,Ci,and REC.Principal component analysis was performed on 14 related indicators after salt stress treatment,and 2 principal components with eigenvalues greater than 1 were extracted,and their eigenvalues were 11.190,2.295,respectively;The first and second principal component variance contribution rates were 79.930%,16.394%,respectively,the cumulative variance contribution rate reached 96.324%,which meets the analysis requirements.According to the ranking of principal component scores,the mitigation ability of exogenous CaCl_(2) to T337 salt stress was T4>T3>T2>T5 from high to low.Therefore,10 mmol/L CaCl_(2) could improve the photosynthetic fluorescence characteristics of T337 rootstock leaves under salt stress,improve the antioxidant enzyme system and osmotic adjustment ability,and enhance the stability and permeability of biofilms to alleviate salt stress.