Effects of drought stresses and times on compensation effect after re-watering in soybean

Abstract: As a kind of abiotic stress, drought stress is a common phenomena existing in the plant growth environment. Although drought could cause negative effects such as plant damaged, it also have a positive compensation effect or super compensation effect on physiological and biochemical metabolism during plant growth and development in a short re-watering period after certain drought stress condition, which could make up the loss or damage. Compensation effect, as an important self-regulation mechanism during plant defense responses or resistant to damage, was widely existed in plants and became an important physiological basis for available water regulation and water-saving high-efficiency agriculture realization. At present, drought is the universal phenomenon in spring, of which it in summer and spring-summer has been common and occurred more frequently and the degree was aggravated in recent years in our country. Therefore, in order to explore the metabolic of growth compensation effect and metabolic compensation effect on soybean drought stress and re-watering and establish the best water-saving irrigation mode, we analyzed the effect of drought stress and re-watering on growth, osmotic regulation, endogenous hormone regulation and anti-oxidation system during different stress periods, stress levels and processing times by weighing control the water content, with Sui Nong 14 as experimental material. The results showed that, plant height and leaf area of soybean were inhibited by drought stress, and the decreasing range was 12.50%-39.74%, 21.71%-52.87% and 16.93%-36.27%, 27.99%-47.80% in seeding stage and flowering stage at 0 d re-watering, respectively. The content of praline, soluble sugar and MDA were increased by 46.97%-131.57%, 99.56%-139.37%, 6.64%-22.82% and 31.68%-136.30%, 32.63%-184.51%, 15.82%-100.75% in seeding stage and flowering stage at 0 d re-watering, respectively. The activity of SOD was increased with a decreasing tendency under 10d severe drought stress. The content of ABA was increased, with GA and ZR decreasing, IAA decreased in seedling stage and increased in flowering period. After re-watering, the daily increasing of plant height and leaf area showed a rapid growth in short-term with the over growth compensation effect, metabolic indices in moderate drought stress and 5 d drought stress treatments returned to control levels with a equal or approximately equal metabolic compensation effect; of which these in serious drought stress and 10 d drought stress treatments were showed an approximately equal or partial metabolic compensation effect. This implied that the occurrence of compensation effect under drought stress after re-watering was conditional. The severe drought stress or long time drought stress could decreased the compensation effect and damaged the plant at last, while the appropriate drought treatments in seedling period could improve drought adaptability and compensation effect under once again the drought stress in flowering. Therefore, a moderate drought resistance exercise should be carried out in seedling stage in order to improve the adaptability with drought environment in the late growing, but not suitable for severe drought stress especially for long time. A best water-saving irrigation mode should be established by reasonable utilization of plant drought compensation effect mechanism so that it could be provide a theoretical for the analysis of compensation effect mechanism and cultivation techniques of drought resistance and high yield on soybean.