Studies On Cold Resistance Identification And Its Physiological And Biochemical Basis In Spring Maize Seedling

Maize cold injury included delayed cold injury, severe cold injury and mixed cold injury.Delayed cold injury usually occurred during maize seedling stage in Northeast China. Due to lowtemperature of the growing season, delayed development caused maize not to mature before frost,water content of grains increased and thousand kenels weight dropped, in the end, yield of grainsdescended. In order to investigate maize cold-resistant mechanism, screening for cold-resistantvarieties in Hei Longjiang province, this study tested and graded forty-four main cultivarscultivated in Northeast China under low temperature stress. Representative varieties were selectedfrom the different cold-resistant grades. (Dong Nong250 and Tong Yu100 were chosen fromcold-resistant varieties; SiMi21 and JiYu4 were chosen from cold-tolerant varieties; TongDan24and JiDong16 were chosen from cold-weak varieties; TunYu88 was chosen from cold-sensitivevarieties). With pot culture, locating five temperature gradients of 5℃, 6℃,7℃,8℃and 9℃, stresstime for one day, three days, five days, seven days and nine days, seven varieties were tested underlow temperature stress in trefoil stage. The physiological and biochemical basis of cold resistancewere definituded by the various physiological indexes indoor. The results as follows:Forty-four varieties contained eight cold-resistant varieties, fifteen cold-tolerant varieties,eleven cold-weak varieties and ten cold-sensitive varieties.Chlorophyll content in the leaves of maize seedlings decreased under low temperature stress,the degree of decline was increased as the intensity of low temperature stress enhancing, but that ofcold-tolerant cultivars was less than that of cold-sensitive cultivars.Peroxidase (POD) activity decreased at the early stage of low temperature stress, then wasinduced to increase, the degree of POD activity was increased as the intensity of low temperaturestress enhancing, that of cold-tolerant varieties increased small; the activities curves of superoxidedismutase (SOD) and catalase (CAT) in the leaves of maize seedlings under low temperature stresswere inverted "V" shape. Variety on the same terms, decline degree of SOD and CAT activitiesincreased as the intensity of low temperature stress enhancing; and temperature on the same terms,decline degree of cold-resistant varieties descended smaller than that of cold-sensitive varieties.The contents of Malondialdehyde (MDA) and free praline increased fast as the stress time andthe stress intensity increasing; the praline content of cold-tolerant varieties increased fast, but thecontent of MDA increased small.Lipid membrane permeability of maize seedlings improved markedly under low temperature stress, relative conductivity of seven varieties increased markedly as the stress intensity increasing,at the same temperature, increased degree increased as resistance weakened.Soluble protein content increased after the first downward trend, when reaching the peak,soluble protein content was significantly higher than the control treatment, declined as thetemperature falled. Temperature on the same terms, decline degree of cold-tolerant varieties wassmaller than that of cold-weak varieties.Relativity analysis of these indexes indicated that besides praline, other indexes reached a verysignificant correlation, relative conductivity, Chlorophyll, MDA, soluble protein, SOD, POD andCAT can be used to identify the cold resistance of maize seedling in this study.