Physiological Effects Of Coronatine On Maize Seedlings Under Low Temperature Stress

Heilongjiang province is located in the northernmost part of China.The temperature of early spring maize sowing is low.Chilling injury has become a major abiotic stress factor threatening the growth and development of Maize in Heilongjiang.Severe chilling injury can reduce maize yield by 22%to 34%.The use of cold resistant species and chemical control treatment can effectively reduce the low-temperature chilling injury of maize seedlings and ensure the increase of final yield.Coronatine（COR）is a novel plant growth regulator that has physiological functions such as promoting cell differentiation,regulating plant growth,and enhancing plant resistance.In order to explore the regulation of cold resistance of maize seedlings by COR,the inbred maize varieties Kr701 and Hei 8834 with different cold resistance were selected as the test materials,and the most suitable concentration was selected from the five COR concentrations by the previous experiment.The effects of COR on the seedling growth,osmotic adjustment system,photosynthetic system and antioxidant system were explored in order to explore its effect on the cold resistance of maize seedling stage,and provide theoretical basis for improving the chilling tolerance of maize at seedling stage in Northeast China.The main results are as follows:1.Normal growth of maize seedlings was inhibited under low temperature stress.COR enhanced the cold resistance of maize by regulating the seedling growth,cell membrane system,osmotic adjustment system,photosynthetic system,and antioxidant system at low temperature,and the comprehensive indicators found that,0.01μmol/L COR has the best regulation effect.2.COR treatment can effectively reduce the inhibition of seedling growth under low temperature stress and enhance plant cold resistance.The specific performance of COR can significantly increase the plant height of maize seedlings under low temperature,ensure the accumulation rate of substances,slow down the reduction of dry and fresh weight in aboveground and underground parts,and promote the growth of seedlings.3.COR treatment can increase its resistance to low temperature by enhancing osmotic adjustment of maize seedlings under low temperature stress.Under low temperature stress,COR promotes the osmotic pressure of the cells,increases the water holding capacity of the tissues,maintains the stability of the cell membrane structure,reduces electrolyte leakage,and reduces the relative conductivity of the seedlings by promoting the content of Pro,soluble protein and soluble sugar in the maize seedlings.Ease the reduction of the relative water content of the plants at low temperatures,thereby reducing the damage to the seedlings.4.COR treatment can enhance the cold resistance of the photosynthetic system of maize seedlings under stable low temperature stress.Under low temperature stress,applying COR can increase the chlorophyll content of leaves,increase Tr,Gs and Ci,increase the Pn of seedlings to a certain extent,maintain the normal operation of the photosynthetic system,increase the photosynthetic productivity of the leaves,and promote the accumulation of the biomass of maize seedlings..5.COR treatment significantly enhanced the antioxidant capacity of maize seedlings under low temperature stress and enhanced their cold resistance.Under low temperature stress,COR can effectively increase the activity of antioxidant enzymes such as SOD,POD,APX,and GR,significantly reduce the content of harmful substances such as MDA and H₂O₂,and the rate of O₂^-production,increase the active oxygen clearance rate of DPPH,and make the Oxygen metabolism maintains balance and reduces oxidative damage to seedlings.6.Different varieties with different cold resistance suffered different degrees of injury under low temperature stress.The injury energy gradually recovered after stress relief,and the recovery rate and degree were also different.The cold resistance variety Kr701 was more inhibited than the cold sensitive variety Hei 8834,and the former recovers faster and stronger than the latter.After the treatment with COR,the cold resistance of maize was enhanced,and the cold resistance of the cold resistant variety Kr701 was stronger than that of the cold sensitive variety Hei 8834.