外源谷氨酸对杨树耐旱性的影响

Effect of Exogenous Application Glutamate on Drought Tolerance of Populus alba×P.glandulosa‘84K’

[目的]谷氨酸(Glu)是植物体内普遍存在的氨基酸,在氨基酸代谢过程中发挥着重要的作用。本研究以银腺杨84K(Populus alba×P.glandulosa‘84K’)为材料,分析外源施加谷氨酸对杨树干旱胁迫下的影响,探讨其在林木响应干旱中的作用,为揭示谷氨酸在林木抗逆性中的作用机制提供参考。[方法]以生长2个月的84K杨为供试材料,分别进行谷氨酸处理后干旱试验和干旱复水试验,观察植株表型,并对叶片含水量、电解质渗透率、谷氨酸含量、渗透调节物质、活性氧含量及活性氧清除酶(CAT、POD和SOD)活性等指标进行分析。[结果]干旱试验表明:谷氨酸处理植株与正常植株相比,显著提高了植物的耐旱能力。经谷氨酸处理的叶片相对含水量增加30.3%、电解质渗透率降低54.0%、谷氨酸含量增加了1.85倍;脯氨酸含量增加33.1%、脯氨酸合成相关基因P5CS、P5CR和P5CDH表达显著升高,分别是对照的2.47倍、2.57倍和8.89倍,而脯氨酸降解基因PDH表达量降低了48.8%。另外,处理后的植株能维持较高的CAT、POD和SOD酶活水平,分别是正常植株的1.67倍、1.35倍、1.17倍,导致过氧化氢含量减少了19.3%。干旱复水试验表明,谷氨酸显著增强了干旱植株的恢复能力。谷氨酸溶液处理植株的叶片相对含水量比未处理植株提高1.08倍,电解质渗透率减少12.1%,脯氨酸含量提高1.09倍,CAT活性和POD活性分别增加了19.0%和62.9%,过氧化氢含量降低31.2%。[结论]外源施加谷氨酸可以提高84K杨叶片谷氨酸含量、诱导脯氨酸合成积累、降低电解质渗透率,减轻干旱胁迫引起的氧化损伤,进而有效缓解植株叶片所受水分胁迫,降低植株对干旱的敏感性。因此,通过外源施加谷氨酸可提高抗氧化能力和渗透调节能力,以提高84K杨在干旱环境下的适应能力,这对揭示谷氨酸在非生物胁迫中的作用起到参考价值。

[Objective]Glutamate is a ubiquitous amino acid in plants,which plays an important role in amino acid metabolism.In this study,poplar 84K(Populus alba×P.glandulosa'84K')was used to analyze the effect of glutamate on the growth of 84K poplar under drought stress,and to explore the role of glutamate in the drought tolerance of 84K poplar.This study provides insights into the amino acid metabolism relating to forest stress resistance.[Method]84K grown for 2 months were subjected to drought after glutamate treatment and re-water to analyze phenotypic and physiological changes,including the leaf water content,electrolyte permeability,glutamic acid content,osmotic adjustment substance content,active oxygen content,active oxygen scavenging enzyme(CAT,POD,and SOD)activity and so on.[Result]The drought test after glutamate treatment showed that glutamate could improve the drought tolerance of plants.Compared with normal drought plants,the relative water content of the leaves increased by 30.3%,the proline content increased by 33.1%,the electrolyte permeability decreased by 54.0%,and the expression of proline synthesis-related genes P5CS,P5CR,and P5CDH significantly increased,2.47 times,2.57 times and 8.89 times higher than that of the control,respectively.The expression of proline degradation gene PDH decreased by 48.8%.In addition,glutamate treatment plants could maintain higher CAT,POD,and SOD enzyme activity levels,which were 1.67 times,1.35 times,and 1.17 times higher than those of normal drought plants,respectively,and the hydrogen peroxide content decreased by 19.3%.The application of glutamic acid after drought significantly enhanced the recovery ability of drought plants.Compared with the re-water plants,the relative water content of the plant leaves increased by 1.08 times,the proline content increased by 1.09 times,the electrolyte permeability decreased by 12.1%,the CAT activity and POD activity increased by 19.0%and 62.9%,respectively,and the hydrogen peroxide content also decreased by 31.2%.[Conclusion]Exogenous application of glutamic acid can increase the endogenous glutamate content of 84K poplar,induce proline synthesis and accumulation,reduce the electrolyte permeability and oxidative damage caused by drought stress,and effectively alleviate the water stress of plant leaves,thus reducing the sensitivity of plants to drought.Therefore,the exogenous application of glutamic acid can strengthen amino acid metabolism,improve antioxidant capacity and osmotic adjustment ability,and improve the adaptability of 84K poplar in a drought environment,which plays a reference value in revealing the role of glutamic acid in abiotic stress.