根区亚低温胁迫下外源GABA对山定子根系抗氧化功能的影响

Effects of Exogenous GABA on Antioxidant Function of Malus baccata Borkh.Roots under Suboptimal Root-zone Temperature

以当年生山定子实生苗为试材,采用温室盆栽土培试验,模拟根区亚低温(5℃)条件,设置亚低温(L)、亚低温+外源γ氨基丁酸(LG)和亚低温+氨己烯酸(LV)处理,分别于处理后0、12、24、48、96和144h后剪取白色幼嫩根系,测定山定子根系内源γ-氨基丁酸(GABA)含量、渗透调节物质含量、活性氧含量和抗氧化酶活性等指标,研究根区亚低温下GABA对山定子根系抗氧化系统的调节效应。结果显示:(1)根区亚低温下,山定子根系内源GABA含量略高于对照,渗透调节物质也不同程度积累,超氧阴离子(O_2^-·)含量、过氧化氢(H_2O_2)含量显著升高,膜脂过氧化程度加深。(2)外源施加GABA进一步促进了内源GABA的积累,明显增加根系中可溶性糖、可溶性蛋白和脯氨酸(Pro)等渗透调节物质含量,显著提高根系的超氧化物歧化酶(SOD)、过氧化氢酶(CAT)、抗坏血酸过氧化物酶(APX)等酶活性,最终使得山定子根系中H_2O_2等的含量降低,膜脂过氧化程度缓解。(3)GABA专一性抑制剂VGB处理后的效果与外源GABA处理结果相反。研究表明,GABA代谢对山定子根系抵御亚低温胁迫引发的氧化胁迫有积极作用,外源GABA具有通过诱导内源GABA代谢提高根系抗氧化能力的生理效应。

The potted seedlings of Malus baccata were used as materials in the treatments of simulated suboptimal root-zone temperature(5 ℃)in culture room.The treatments included the suboptimal root-zone temperature(L),L +exogenous GABA(LG)and L + VGB(LV),the white roots were cut at 0,12,24,48,96,and 144 hafter treatment,respectively.We measured the contents of endogenous GABA,osmotic adjustment substances and reactive oxygen species,the activities of antioxidant enzymes to investigate the regulating effect of GABA on the antioxidant system in roots under suboptimal root-zone temperature.The results showed that:(1)the endogenous GABA content in the roots of Malus baccataincreased under the L treatment,osmotic adjustment substances accumulated in different degrees.And as a consequence,the contents of superoxide anion (O2-) and hydrogen peroxide(H2O2)increased significantly.The peroxidation in roots was deepened.(2)Exogenous GABA increased the contents of endogenous GABA in roots,soluble sugar,soluble protein and proline(Pro)in the roots,significantly enhanced the activities of superoxide dismutase(SOD),catalase(CAT)and ascorbate peroxidase(APX)in roots,and effectively reduced the contents of H2O2 and O2-,which meant exogenous GABA could significantly alleviate the degree of membrane lipid peroxidation.(3)The effect of VGB,which is the specific inhibitor of GABA(LV),treatment was opposite to that of LG treatment.Those results indicated that the GABA metabolism had a positive effect on the defense of the roots to the oxidative stress triggered by suboptimal rootzone temperature,and exogenous GABA had the effect of enhancing the antioxidant capacity of the roots through regulating endogenous GABA metabolism.