γ-氨基丁酸对番茄嫁接苗耐盐性的生理调控效应

Physiological regulation of γ-aminobutyric acid on the salt tolerance of grafted tomato seedlings

[目的]γ-氨基丁酸(GABA)可增强作物品质和抗逆性,但其效果是否受植株根系耐盐性的影响尚不明确。因此,研究添加外源GABA对不同耐盐性番茄嫁接苗的生理调节机制及生长的影响,为小分子氨基酸在蔬菜生产中的应用提供理论依据。[方法]以耐盐性较强的砧用番茄‘OZ-006’为砧木、对盐分较敏感的‘中杂9号’为接穗形成的嫁接苗(RS)为材料,以‘中杂9号’自嫁接苗(SS)为对照材料,进行无土营养液栽培试验。以Hoagland营养液为基础,以调节NaCl浓度至175 mmol/L形成的盐胁迫条件作为对照(CK),在CK基础上设置添加5 mmol/L GABA处理(+G)。从处理后3天起,测定了幼苗生长、Na^(+)积累、氨基酸含量及活性氧代谢指标。[结果]随着NaCl胁迫时间的延长,SS和RS幼苗均显著受到盐胁迫伤害,但RS幼苗盐害指数及Na+含量显著低于SS幼苗,其生长速率、叶绿素含量及氨基酸含量显著高于SS幼苗,其O2·-和MDA含量显著低于SS幼苗,表现为耐盐性显著高于SS幼苗。添加外源GABA后,SS和RS幼苗的鲜重、生长速率、叶绿素及氨基酸(GABA、谷氨酸和脯氨酸)含量、抗氧化酶(SOD、POD和CAT)活性均显著提高,根系和叶片内Na+含量、O2·-产生速率及MDA含量均显著降低,且SS幼苗耐盐性提高的效果大于RS幼苗。[结论]盐胁迫显著影响番茄幼苗的生长,尤其对耐盐性弱的品种生长抑制更加显著。γ-氨基丁酸(GABA)可有效提高番茄嫁接苗的耐盐性,主要原因在于GABA为幼苗提供了氮素营养,促进了盐胁迫下植物的生长和叶绿素的合成,同时GABA诱导细胞内多种氨基酸含量上升,叶片渗透调节能力增强,从而抑制了Na^(+)过量积累,缓解了细胞内活性氧积累带来的膜伤害。此外,GABA添加对耐盐性弱的番茄嫁接苗耐盐性的提升效果比对耐盐性强的番茄嫁接苗更加明显。因此,在盐胁迫条件下,施用外源小分子氨基酸(如GABA)可能是提高作物耐盐能力的有效措施。

[Objectives] γ-Aminobutyric acid(GABA) plays an important role in enhancing crop quality and stress resistance.We studied the effects of exogenous GABA on salt tolerance of plants through the growth and the physiological responses under salt stress,to provide theoretical base for the application of small molecular weight amino acid against salt stress in vegetable production.[Methods] Soilless culture method was used for this research.The salt-tolerant tomato seedlings were grafted the scions of salt-sensitive cultivar ‘Zhongza 9’ onto the rootstocks of salt-tolerant cultivar ‘OZ-006’(RS),the less tolerant seedlings were self-grafted of ‘Zhongza 9’(SS).The salt stress condition was made by adding 175 mmol/L of NaCl in the basic Hoagland nutrient solution,and 5 mmol/L of GABA was added as treatment.Since the tomato seedlings were treated three days,the growth,Na^(+) accumulation,amino acid content and active oxygen metabolism indices of the seedlings were measured.[Results] Both SS and RS seedlings were significantly injured by salt stress with the extension of NaCl stress time,however,the RS seedlings had significantly lower salt damage index and Na^(+) content,significantly higher seedling growth rate,chlorophyll content and total amino acid content,and significantly lower O2·- production rate and MDA content,compared with those of SS seedlings.The addition of GABA significantly increased the fresh weights,seedling growth rates,chlorophyll contents and the amino acid contents(especially GABA,glutamic acid and proline),antioxidant enzyme(SOD,POD and CAT) activities,while significantly reduced Na^(+) content,O2·-production rate and MDA contents in roots and leaves of both SS and RS seedlings,compared with respective controls.Furthermore,the effect of exogenous GABA on improving the salt tolerance of SS was greater than that of RS.[Conclusions] Salt stress significantly affects the growth of tomato seedlings,especially the salt intolerant varieties.GABA could effectively improve the salt tolerance of both salt tolerant and sensitive tomato seedlings.The reason for this effect may be that,GABA provides nitrogen nutrition for seedlings and promotes plant growth and chlorophyll synthesis under salt stress.The addition of GABA induces the increase of multiple amino acid contents in cells and the enhancement of osmotic adjustment ability of leaves,thus inhibits the accumulation of Na^(+) and alleviates the damage caused by the accumulation of intracellular reactive oxygen species.In addition,the mitigation effect of the salt damage is more obvious in salt sensitive seedlings.Therefore,under salt stress conditions,the application of exogenous small molecular weight amino acids,such as GABA,may be an effective measure to improve the salt tolerance of crops.