The Regulating Effect Of Seed Coating Agents On The Growth Of Cotton Seedlings Under Low Temperature Stress

Objective: In order to explore the mechanism of seed coating agents, the effect of different seed coating agents on cotton seed germination, seedling growth and physiological indexes under low temperature stress was studied, therefore providing theoretical support for the application of seed coating technology and theoretical basis for systematic research on physiological mechanism of cotton to low temperature.Methods: Combined with the previous research on low temperature resistant cotton seed coating agents; in accordance with the rules of guidelines on drafting standards of suspension concentrates for seed coating agents and germination indoors to select seed coating agents of resistance under low temperature stress. Using selected seed coating agents No.1, No.3 and No.4 coated cotton seeds indoors, respectively, cotton seed and seedlings were treated under different artificial low temperature treatment, the cotton seed germination and seedling rate were investigated at time treatment. Conductance method was used to determine the conductivity of cotton seedlings under different seed coating treatment. Spectrophotometric method was used to determine the physiological indexes to reveal the regulation effect of seed coating agents on the growth of cotton under low temperature stress.Results: Cotton seed coating agents were screened through a lot of experiments on cotton seed, and the best ratio of each component, low temperature resistant cotton seed agents in line with the objectives were developed. The appearance of the agent was light red liquid, slightly acidic p H, low loss rate, short film forming time, small particle size, all below 3μm, D50 0.560μm, D90 1.036μm, qualif ied viscosity and suspension, good cold and thermal storage stability, which was up to the national industry standards. Screened seed coating markedly increased the cotton seed germination rate and seedling emergence rate under low temperature stress and protected the physiological system.No.1, No.3 and No.4 seed coating agents can signif icantly improve the cotton seed germination rate and seedling rate, promote the stalk thickening, biomass accumulation and root elongation and enhance seedling resistance ability under different low temperature stress.Relative electrical conductivity of seed coating agents cotton leaves increased, but it increased even more in the uncoated treatment under low temperature stress. MDA content of cotton seedlings leaves in the uncoated treatment increased by 200% compared with 0 d, while it increased 25%-95% in the coated treatment. These three seed coating agents all can significantly improve the antioxidant enzymes activity in leaves of cotton seedlings, compared with the uncoated treatment, SOD activity increased by 40% in the seed coating No.1 treatment. No. 3 agents increased nearly 15%, No. 4 agents increased 45%. POD activity showed an upward trend with the stress time prolonged, which increased by 4% to14%. Soluble sugar content in cotton seedling leaves was 7 to 10 times compared with 0 d. On the fifth day after low temperature treatment, the content of soluble protein in leaves of cotton seedlings respectively increased 82%, 86%, 68% and 101% compared with 0 d; proline content in cotton seeding leaves increased more than 2 times compared with 0 d, which generally showed an upward trend under low temperature stress.Conclusions: Low temperature resistant cotton seed coating agents were developed in this experiment. Screened 3 kinds of seed coating agents all could increase cotton seed germination rate and seedling survival rate, promote stalk thickening, cotton seedling biomass accumulation and root elongation of cotton seeds under low temperature stress; seed coating treatment could reduce the increase degree of relative conductivity and MDA content of cotton seedling leaves under low temperature stress, increase soluble sugar, soluble protein, proline content, SOD and POD activity, promote the growth and development of cotton seedlings, which protected the seedling physiological system and alleviated the damage of low temperature stress on cotton seedlings. Seed coating No.1 had the best treatment effect.