Effects Of γ-Aminobutyric Acid On Tomato Seed Germination And Seedling Growth Under Salt Stress

Due to its unique natural climate and planting area advantages,Xinjiang has became a major tomato-producing area.However,soil salinity is widespread due to climatic reasons,and it is urgent to study exogenous substances to alleviate the damage of tomatoes under salt stress.In this study,two different salt-sensitive tomato varieties were used as test materials,and the effect of exogenous GABA on different salt-sensitive tomato varieties under salt stress was investigated by adding GABA（γ-aminobutyric acid）to tomato seeds and seedlings under Na Cl stress.The effects of seed germination indicators,seedling agronomic traits indicators,reactive oxygen species metabolism,seedling root architecture,photosynthetic pigment accumulation and leaf photosynthetic parameters were screened out.provide a theoretical basis.The main findings are as follows:（1）The effects of exogenous GABA at different concentrations(1.25-20 mmol·L^-1)on the seed germination of two different salt-sensitive tomato cultivars under Na Cl stress were studied by seed soaking.The results showed that the treatment of 1.25 mmol·L^-1GABA promoted the germination potential,the number of lateral roots and the growth of seed germ in the’M82’tomato cultivar.In’IL-7-5-5’tomato cultivar,the low concentration Seed soaking with GABA(≤2.5 mmol·L^-1)promoted the germination potential and germination index of tomato seeds,and high concentration GABA soaking(≥1.25 mmol·L^-1)promoted the increase of the number of lateral roots.（2）Compared with the control,Na Cl treatment inhibited the seedling growth of two different salt-sensitive tomato varieties.Under Na Cl stress,exogenous GABA treatment alleviated the damage and inhibition of tomato seedling phenotype and seedling growth.Under the treatment of 35 mmol·L^-1GABA,the morphological indexes of the seedlings of two tomato varieties were improved.The alleviation effect of external application of GABA on seedlings was related to time,and long-term application of GABA would reduce the accumulation of root system.（3）Compared with the control,under Na Cl stress,exogenous GABA treatment can increase the activities of antioxidant enzymes（SOD,POD and CAT）in leaves of two tomato varieties,and reduce MDA,endogenous H₂O₂content and O₂^-The production rate and there is a certain concentration effect,’M82’tomato cultivar with 15 mmol·L^-1and 35 mmol·L^-11 concentrations of GABA has the best alleviation effect,’IL-7-5-5’tomato cultivar with 25 mmol·L^-1concentration and 35 mmol·L^-1concentrations of GABA had the best alleviation effect.（4）Compared with the control,exogenous GABA treatment could increase the total length,total surface area,average diameter and number of root tips of seedlings of two tomato varieties under Na Cl stress.On the third day of treatment,35 mmol·L^-1GABA treatment improved the root architecture of two tomato cultivars,and found that with the extension of exogenous GABA treatment time,the alleviation effect of exogenous GABA on Na Cl stress gradually decreased.（5）Compared with the control,under Na Cl stress,exogenous GABA treatment could increase the contents of chlorophyll a and chlorophyll b in the leaves of the two tomato cultivars.Ci and Gs values?of‘IL-7-5-5’tomato seedlings were up-regulated,indicating that exogenous GABA can regulate the chlorophyll content and photosynthetic function of tomato seedling leaves under Na Cl stress,and play a positive role in enhancing the salt tolerance of tomato leaves.Exogenous GABA solution could improve the seed germination and seedling growth of two different salt-sensitive tomato species under Na Cl stress.Therefore,it is recommended to use 1.25 mmol·L^-1GABA for seed soaking in the germination stage,and 35 mmol·L^-1GABA for watering in the seedling stage to relieve Na Cl stress.