Effects Of Soaking Seeds With H₂O₂ On Growth And Antioxidant System Of Rape Seedlings Under Low Temperature Stress

Rapeseed is an important oil crop in China.Winter rapeseed area in the Yangtze River Basin is the largest main rapeseed producing area in China.With the change of cultivation system in this area,the stubble of rapeseed was delayed,and with the increasing shortage of labor resources in rural areas,farmers’ demand for Simplified Cultivation Methods of rapeseed direct seeding was increasing,so late direct seeding rapeseed emerged as the times require.However,late direct seeding rapeseed is vulnerable to low temperature.Under adverse environmental conditions,rapeseed seed vigor decreases,germination seedlings are blocked,seedling vigor is weak after emergence,and it is vulnerable to cold injury and freezing injury in winter,affecting the growth and development of late plants.In this experiment,Brassica napus L.Nannongyou No.4 was used as experimental material to study the effects of low temperature soaking with hydrogen peroxide on Seed Germination and seedling growth of rapeseed and on the antioxidant system of rapeseed seedlings.The physiological mechanism of H2O2 soaking on Rapeseed under low temperature stress was discussed,which provided theoretical basis and practical technology for rapeseed seedlings growing fast,uniform and strong in late direct seeding.The test results show that:1.Soaking seeds with hydrogen peroxide(H2O2)can improve seed germination potential,which is more consistent with the process of rape population germination.The delay of sowing date,the prolongation of seedling emergence time,the decrease of seedling growth rate and the increase of young stem shrinkage rate and freezing injury index indicated that low temperature had a significant inhibitory effect on the germination of rapeseed seeds,and the seedling vigor grew at low temperature was weak,and the adaptability to the environment was poor.Soaking with H2O2 accelerated the germination process of rapeseed seedlings to a certain extent,increased the seedling rate of rapeseed seedlings,reduced the incidence of young stem shrinkage and freezing injury index in the growth process,which indicated that soaking with H2O2 enhanced seedling vigor to better adapt to environmental changes,alleviated the inhibition effect of low temperature on rapeseed growth,and increased dry matter accumulation in the above ground parts of rapeseed.2.The response of antioxidant system of seedlings of different leaf ages to chilling and freezing stress is different.Under low temperature stress,ROS accumulated in plants and MDA content was higher.Soaking seeds with H2O2 increased the activities of three antioxidant enzymes,superoxide dismutase(SOD),peroxidase(POD),catalase(CAT),and more effectively regulated the activity and content of ascorbic acid peroxidase(APX),etc in A-G circulatory system,which made the removal of excessive ROS more efficient and the content of MDA lower.The results showed that soaking seeds with H2O2 could increase the activity of antioxidant enzymes and the content of antioxidants,reduce ROS damage and improve cold resistance of rapeseed,thus increasing the accumulation of dry matter in rapeseed.