Abscisic Acid Can Improve the Salt Tolerance and Yield of Rice by Improving Its Physiological Characteristics

Salt stress exerts a notable influence on rice's normal growth and development process. It causes a decline in rice yield, and in certain extreme cases can lead to the complete failure of rice crops. Abscisic acid, also known as S-ABA, may play an important role in regulating rice plant responses to various stressors and promoting crop growth against adversity. In this research, the impact of externally applied S-ABA (0.03% S-ABA, diluted 100 times) on the growth and yield of rice was explored. The experiment made use of the traditional rice variety Huanghuazhan as the test material. The study focused on how S-ABA affected rice at various growth phases under salt-stress conditions. The effects of S-ABA sprayed once (three-leaf/one-heart stage) and twice (three-leaf/one-heart stage, break stage) on the photosynthetic characteristics, antioxidant metabolism, membrane lipid peroxidation products, osmotic regulation, and yield of rice under 0.4% NaCl were studied. The experimental outcomes indicated that the presence of salt stress had a restraining effect on the growth of rice. There was a notable decline in the net photosynthetic rate; moreover, the yield was diminished by 26.90%. Salt-induced stress clearly imposed negative impacts on these aspects of rice's physiological functions and productivity. The exogenous application of S-ABA was highly effective in mitigating the inhibitory influence of salt stress on the growth of rice. When S-ABA was sprayed on two occasions, there was a notable increase in the total chlorophyll content within the rice leaves, ranging from 7.40% to 80.99%. This led to an enhancement in the photosynthetic ability of the plants. Additionally, the growth of rice seedlings was significantly promoted. The activity of antioxidant enzymes also witnessed an upward trend, and the content of soluble protein increased by 0.87-2.60%. The content of malondialdehyde and hydrogen peroxide were decreased by 4.18-12.49% and 13.71-52.18%, respectively, the damage to membrane lipid peroxidation was alleviated, and rice yield was increased by 14.84% and 29.29% after spraying S-ABA once or twice under salt stress, respectively. In conclusion, salt stress inhibits the growth and development of rice during grouting and destroys the antioxidant system of the rice plant, thus reducing its yield. Leaf spraying with S-ABA can alleviate the degradation of chlorophyll, enhance the photosynthesis, antioxidant system, and osmotic regulation ability of rice, reduce salt-stress damage, and thus alleviate the yield loss under salt stress to a certain extent. In addition, the regulation effect of two sprayings of S-ABA is better than that of one spraying. The results of this study revealed the physiological regulation mechanism of S-ABA at different growth stages of rice under salt stress, and provided theoretical support for the reduction of salt-stress damage to rice. This suggests that S-ABA has potential applications in the improvement of salt tolerance in rice.