Screening Of Cold Resistance Of Different Maize Cultivars And Effects Of Low Temperature On Photosynthesis And Physiology Mechanism Of Maize During Seeding Stage

This study aims to evaluate the cold resistance ability of 45 maize cultivars according to the indexes of germination including germination potential, germination rate, germination index. Synthetic evaluation value(D) and subordination function method were applied in the study. Base on the results, 23 varieties were chosen to evaluate the cold resistance ability during seeding stage by measuring Chlorophyll content、POD content、MDA content and Pro content. Furthermore, To study the response mechanism of photosynthetic fluorescence of maize varieties with different low temperature tolerance, Jidan159 witch is more sensitive to low temperature and Xianyu335 with higher tolerance to low temperature were treated with 1、3、5、7days of low temperature in this study when they were at four leaves with one shoot stage. Results are as following: 1 Evaluation and screening of cold resistance of different maize cultivars during germinationResults showed that Hengyu709 and Dayu M737 have the highest cold resistance. According to synthetic value(D), the 45 maize cultivars were clustered into four groups: Group A, D>5.4, 8 cultivars, highest cold resistance; Group B, 4.2<D<5.4, 13 cultivars, higher cold resistance; Group C, 3.5<D<4.2, 12 cultivars, lower resistance; Group D, D<3.5, 18 cultivars, cold sensitive. 1 Evaluation and screening of cold resistance of different maize cultivars during seeding stageHengyu709 、 Yanfeng508 、 Dayu M737 、 Jinongda885 、 Zhengdan958 were high resistance cultivars; Ping’an185、Lvyu9915、Heyu3 Jisheng385、Jiudan100 were moderate resistance cultivars; Dedan1002、Xianyu335、HM217、Tieyan36、Yulong9、Chuangshi998、XH84 were low resistance cultivars; Dongdan213、W1521、Jundan6、Linong24、Lvyu4117、Changdan297 were cultivars sensitive to low temperature. 3 Effects of low temperature on Mechanism of Photosynthetic Fluorescence of maize during seeding stageChlorophyll content photosynthetic intensity and chlorophyll fluorescence parameters of two varieties both changed with the extend of time and restore again after certain days. Xianyu335 with higher tolerance to low temperature was less affected than Jidan159 by the low temperature stress, and need less time to restore. 4 Effects of low temperature on physiological mechanism of maize leaves during seedling stageXianyu335 with higher tolerance to low temperature was less affected than Jidan159 by the low temperature stress, the content of soluble protein and soluble sugar raised at the early stage of low temperature treatment, so did the protective enzyme activity,while the content of MDA declined, and showed a negative correlation with the protective enzyme activity, which shows that varieties with higher tolerance to low temperature can adjust oxygen mechanism quickly during short time low temperature treatment, while with the extend of the low temperature treatment, this kind of adjustment became invalid, however, the variety with higher tolerance to low temperature still affected less than the variety is sensitive to low temperature. The disorder of reactive oxygen mechanism is the main reason cause the low temperature stress to maize leaves,short time low temperature treatment could accelerate the protective element, but with the extend of low temperature treatment regulating system will fail which leads to the chilling injury, the variety with higher tolerance to low temperature still affected less than the variety is sensitive to low temperature.