| Maize is a typical C4plant that is thermophilic and photophilous,which requires high temperature conditions,and is generally weak in cold tolerance. Maize is an important food crop. Therefore the level of the productional situation and the benefit is directly related to the increase of the production, income and sustainable agricultural development, having a greater impact on China ’s maize production and maize market trends,Even having a significant impact on global maize prices.The low temperature in the spring is an important meteorological disasters of maize production. Due to the damage of the cold, the fluctuations of the maize production between interannual is larger, the maize quality is also greatly affected. For this reason, research on maize chilling is timeliness and necessary. Choices of the Maize parent plants directly affect the physiological indicators of F1, thereby affecting its ability of cold tolerance and production. The improvement of the ability of the cold tolerance and yield of the parental inbred lines not only significant cost savings, laiding a solid foundation of more promotion of varieties, so the research on the cold tolerance of maize inbred lines is of great significance. Low temperature makes seed germination rate drop lowly, the greater the degree of stress low,the smaller germination rates is. For this study around the maize inbred lines of Heilongjiang Province cold stress treatment measuring the germination rate and seedling growth vigour under the stress of the low temperature, initially screening the resistantance to the low temperature of all varieties, and laying the foundation for maize breeding, providing a theoretical basis for agricultural production for breeders to chose materials being resistantant to temperature, which is important for the increase of the income and efficiency.In this experiment,20common inbred lines of Heilongjiang Province were used for maize cultivars to make the low temperature screening on the bud and seedling stage, making cluster analysis, choosing six inbreds which have different ability of cold resistantance, and indoor pot experiment and low temperature test, physiological and biochemical and molecular biology techniques were used to study the five low stress levels under (8℃,6℃,4℃,2℃,0℃) and low temperature processing physiological and biochemical response of maize seedlings physiological and biochemical changes after the resumption of normal temperature, low temperature stress to explore maize and restorative strength of resistantance mechanisms to provide a theoretical basis for further breeding cold resistantant maize varieties and identification methods.Below are the results:1.The cold temperature makes Seed germination rate dropped, the greater the degree of stress was, the smaller low germination rate, the longer the time required for germination was.2. The cold temperature makes the conductivity of maize seedling leaves, SOD activity, POD activity, MDA content increased, within a certain range, the lower temperature was,the greater the amplitude was, when the outside temperature was too low, in addition to the increase of the conductivity,SOD activity, POD activity, MDA content did not grow.3. By clustering bud stage of analysis, the20species were divided into three types,5varieties such as Ye478are resistantant to low temperature;7varieties such as He344are intermediate;8other varieties such as Kat853are of sensitivity, by clustering analysis of the20species were divided into three types,6species such as Ye478are resistantant to low temperature; eight varieties such as intermediate;6other varieties such as Kat853are of sensitivity. Shows that cold tolerance on the bud and seedling stage shoots has some correlation coefficient from the cluster analysis of shoots.4Cold Stress made maize leaf photosystem Ⅱ (PS Ⅱ) activity centers damaged. The lowered Temperature made initial fluorescence Fo of the leaves of six inbred lines of maize increased, Fv/Fm, Fv/Fo were decreased overall, and with the low stress levels to strengthen,the larger the range of increase or decrease,the larger range of the varieties with strong resistantance changes to a lesser extent, the weak inbred varieties resistantant PS Ⅱ more serious damage to the blades.5. The protective activity of the protective enzyme in the maize strong resistant to cold stress is the largest,and the the protective activity of the protective enzyme in the varieties weak resistant to cold stress is smallest. With the aggravation of low temperature stress, The SOD, POD activity of protective enzymes maize seedlings strong resistant to cold stress showed a trend to increase. The SOD, POD activity of protective enzymes maize seedlings weak resistant to cold stress showed a trend to upwartl, at2℃and0℃low temperature, SOD, POD activity was downward trend, but higher than the control, due to the low temperature on leaf membrane system damage is more serious, beyond the protection and function of protective enzymes.6. Cold Stress made leaf membrane systems of maize suffered some damage, maize seedlings weak resistant to cold stress at low temperature stress suffered the greatest damage. Under each low temperature stress, the membrane permeability of maize seedlings were increased, electrical conductivity continues to increase with temperature decreasing, MDA levels were elevated, the extend of South9808weak resistant to cold stress is the largest.7. The leaf initial fluorescence Fo of the three types of maize at each temperature stress after return to room temperature droped, Fv/Fm, Fv/Fo showed an upward trend overall, due to the small damage of maize strong resistant to cold stress, recovery1-2d has recovered to the normal level, but after3d restore the injured heavier species did not reach normal levels, indicating that recovery time of more severe damage PS II species is more than3d.8. Recovery after treatment at different temperatures in different activities of protective enzymes resistantant varieties of different degree of recovery, but higher than the control Different varieties under8℃,6℃low temperature recovery remained the same, the3d are restored to normal levels, the treatment temperature is too low,such as under2℃and0℃treatment, protective activity of the intermediate species and varieties of cold-sensitive is not returned to normal levels in3d, the activity remained high, protective activity of some species such as the South9808restore normal temperature protection but increased activity, indicating that the membrane damage was more serious, need to be restored to normal levels in more than3d.9. Conductivity and MDA content in different resistantant varieties were decreased after treatment at different temperatures recovery, breed being smaller hurt hade a faster recovery rate, the varieties being heavier hurt recovered slowly, needed more than3d.10. The growth of all varieties of different types at8℃low temperature recovery after3leaf were higher than controls, indicating that the treatment of8℃Clow temperature treatment can increase the growth rate of heart leaves of maize seedlings;the growth rate heart leaves of Ye478, K10, M8, South9808in3d recovery after6℃low temperature treatment were higher than the control,the heart leaf growth of He344, Kat853is less than the control, indicating after6℃low temperature can increase the leaf growth of maize seedling strong resistant to cold stress;4℃,2,0℃treatment decreased the growth rate of heart leaves of maize seedlings, such as the leaf growth of varieties of different types in recovery3d after0℃treatment reduced. |
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