A Preliminary Study On BABA-induced Resistance To Alkaline Stress In Tobacco

Tobacco is an important agricultural economic crop in China,which contains abundant amino acids and medicinal nicotine.But under salt and alkali stress,tabacco is seriously inhibited and the yield is obviously reduced.?-aminobutyric acid?BABA?is a non-protein amino acid and it is a good plant growth regulator.BABA can induce plants to resist many biological and abiotic stresses but no study reported to induce tobacco to be resistant to alkali stress.In this paper,we will use Yunyan 87 as a test material to exert BABA treatment to exert its regulation on the antiquization of tobacco,and explore its mechanism from the aspects of antioxidant system,ion transport and gene expression.The results are as follows:1.The exogenous 0.2 mmol/L and 0.5 mmol/L BABA could significantly increase the root length and fresh weight of tobacco under alkali stress.The relative water content of tobacco was increased and the chlorophyll content was significantly improved.The symptoms of stress damage caused on tobacco are greatly alleviated;2.Under the stress of alkali stress,tobacco seedling was subjected to severe oxidative stress and exogenous 0.2mmol/L and 0.5mmol/L BABA could significantly increase the contents of antioxidants such as GSH,ASA and carotenoids.It enhanced the non-enzymatic antioxidant system of tobacco.The activities of superoxide dismutase?SOD?,ascorbate reductase?APX?,peroxidase?POD?and catalase?CAT?in tobacco seedlings were also enhanced and It enhanced the enzymatic antioxidant system.And then the content of MDA and H₂O₂ decreased,making the membrane membrane by the membrane lipid peroxidation weakened,the relative conductivity decreased;3.In the case of alkali stress,tobacco will improve its ability to penetrate osmotic stress by synthesizing proline.After treatment with 0.2 mmol/L and 0.5 mmol/L BABA,tobacco increased the synthesis of soluble and soluble sugars to relieved the osmotic stress and reduced the dependence on proline synthesis.4.Under the single alkali stress,the content of organic acids in the aerial part of tobacco increased while the content of organic acids in the roots decreased.The content of organic acids in the two parts after BABA treatment increased.It could alleviate the high pH toxicity caused by alkali stress by inducing more organic acids to synthesize tobacco.5.The contents of Na+ and Ca²⁺) in tobacco increased,K+ and Mg²⁺ contents decreased under single alkali stress.After BABA treatment,tobacco was induced to decrease Na+ content,increase K⁺ and Mg²⁺ uptake,maintain cell ion balance and decrease ion toxicity.6.The result of relative quantitative PCR showed that BABA could induce the expression of NtCaM calmodulin family gene and ABC transporter family gene to regulate the transport and growth and metabolism of GSH1 and PROX1,and promote GSH synthesis and proline metabolism.The above evidence suggested that BABA induced tobacco to defense alkaline stress was the result of antioxidant,organic acid synthesis,ion transport and gene expression.