外源柠檬酸对铝胁迫下马尾松生理特性的影响

Effects of Exogenous Citric Acid on Physiological Characteristics of Pinus massoniana under Aluminum Stress

【目的】研究受铝毒的马尾松幼苗施加外源柠檬酸后的一系列生长及生理特性变化,确定柠檬酸最佳缓解浓度,揭示柠檬酸缓解马尾松铝毒的生理机制,为土壤酸化地区马尾松的生长提供理论依据。【方法】以2种不同家系马尾松幼苗(耐铝型FJ5、铝敏感型GD20)为试验材料,采用水培法研究不同浓度柠檬酸对铝胁迫下马尾松幼苗株高增量、根系形态及其针叶中抗氧化酶[过氧化物酶(POD)、超氧化物歧化酶(SOD)、过氧化氢酶(CAT)、抗坏血酸过氧化酶(APX)、谷胱甘肽还原酶(GR)]活性、活性氧(H_2O_2和O_2^(-·))、渗透调节物质(可溶性糖、可溶性蛋白、游离脯氨酸)和丙二醛含量的影响,并运用主成分分析法探讨外源柠檬酸缓解马尾松铝毒过程中起主导作用的生理指标。【结果】铝胁迫下2种家系马尾松幼苗根系总长、表面积、体积、直径及株高增量均降低,针叶内抗氧化酶活性增强,H_2O_2、O_2^(-·)、MDA和渗透调节物质含量均有所升高。经柠檬酸处理后,2种家系马尾松根系总长、表面积、体积、直径及株高增量均有所增加,其针叶内抗氧化酶活性增强,H_2O_2、O_2^(-·)、MDA和渗透调节物质含量均相应减少,且GD20变化幅度大于FJ5。主成分分析得出第一主成分中各指标贡献率大小为MDA>H_2O_2>脯氨酸>GR。【结论】活性铝对马尾松幼苗生长产生一定的毒害作用;外源柠檬酸能有效缓解马尾松的铝毒作用,且对铝敏感型马尾松的缓解效果好于耐铝型。柠檬酸缓解铝毒的效果因浓度不同而存在差异,0.02 mmol·L-1的柠檬酸解毒效果最佳,当浓度大于0.08 mmol·L-1时,缓解效果受到抑制。MDA和H_2O_2可能是外源柠檬酸缓解铝毒作用的关键指标。

【Objective】 This paper investigated the effects of exogenous citric acid on a series of growth and physiological characteristics of Pinus massoniana seedlings under aluminum toxicityto find the optimal alleviating concentration of citric acid,and reveal the physiological mechanism how exogenous citric acid alleviates aluminum toxicity,in order to provide theoretical basis for the growth of P. massoniana in soil acidification areas.【Method】In this study,two different families of P. massoniana seedlings（aluminum-resistant FJ5,aluminum-sensitive GD20） were used to investigate the effects of exogenous citric acid on P. massoniana subjected to aluminum stressin a hydroponic experiment.The height increment contents,the form of root,as well as the activities of antioxidant enzymes（POD,SOD,CAT,APX,GR）,the contents of active oxygen（H2O2 and O2（-·））,osmotic adjustment substances（soluble sugar,soluble protein,free proline） and malondialdehyde（MDA） in the leaves of P. massoniana seedlings were measured under different concentrations of exogenous citric acid. The Principal Component Analysis was applied to explore the main physiological indexes during the process of exogenous citric acid to alleviate the aluminum poisoning of P. massoniana. 【Result】Aluminum stress decreased the length,surface area,volume,diameter of P. massoniana seedling roots and the height increment,inscreasedthe activities of antioxidant enzymes in the leaves,and the contents of H2O2,O2（-·）,MDA andosmotic adjustment substances in the leaves. After applying exogenous citric acid,the length,surface area,volume,and diameter of the root,and the seedlingheight increment increased,the activities of antioxidant enzymes in the leaves enhanced,and the contents of H2O2,O2（-·）,MDA and osmotic adjustment substances in the leaves reduced. Compared with FJ5,GD20 had greater change range. Principal component analysis showed that the contribution rate of each index in the first principal component was MDA 〉 H2O2 〉 Proline〉 GR.【Conclusion】Active aluminum has an obvious toxic effect on P. massoniana seedlings; Exogenous citric acid could effectively alleviate the toxicity of aluminum on P. massoniana seedlings,and it had a better effect on aluminum-sensitive variety than aluminum-resistant variety. The alleviating effect of exogenous citric acid on the aluminumtoxicityvarieddependent on the different concentrations of citric acid. The optimum concentration of citric acid was 0. 02 mmol·L-1 among all applied concentrations,and whenthe concentrations was greater than 800 mmol · L-1,the alleviating effects of citric acid was inhibited. MDA and H2O2 may be the key indexes of exogenous citric acid to alleviate aluminum toxicity.