| With Zhengmai366,Yumai34,Yanzhan4110 and Zhengmai9203 being testing materials, a simulated frost experiment was conducted to study the cold resistance of various winter wheat in different jointing stage at the agrometeorological station of Zhengzhou city, Henan province from 2014 to 2015. There are three observed jointing stages:the early stage(5d), the middle stage(10d) and the late stage(15d), and the there observed temperature are -3℃,-5℃ and -7℃. By taking Zhengmai 366 as a sample, the effects of frost on photo synthetic parameters and the accumulation and distribution of dry mater of wheat in different jointing stage was systematically studied. The results can be used to support the warn and reduce the cold injury of the winter wheat in jointing stage. The main conclusions are as follows:Under the conditions of the experiment, the cold resistance of winter wheat begins to drop after entering the jointing stage. Weak winter wheat in the middle jointing stage(10d) was sensitive to frost reaction the most, while weak spring wheat in the late jointing stage(15d) was sensitive to frost reaction the most At -3℃. the enzyme SOD,POD and CAT of all winter wheat are more active than the compared group, which exemplifies a certain cold resistance. The cold injury increases with the temperature being lower and lower. When it comes to -5℃, noticeable differences emerge in the enzymatic activity of different winter. Zhengmai366 shows stronger enzymatic activity than Yumai34, and Zhengmai9023 shows stronger enzymatic activity than Yanzhan4110, and the amount of MDA holds the contrary situation. At-7℃, the enzymatic activity of all wheat reaches the lowest level while the amount of MDA reaches the peak.The chlorophyll content carotinoid content drops significantly in the frost.The range of the Chlorophyll change depends not only on temperature, but also on the stage. In early stage(5d),-3℃, chlorophyll and carotinoid content are higher than CK, with the leaf maturing and temperature reaching low, the compound of chlorophyll and carotinoid is hindered, and the contend declines. The decline of net photosynthetic rate depends on both the temperature and stage. Under the same temperature, the falling range of net photosynthetic rate is 10d>15d>5d, and the frost has little effects on net chlorophyll rate in heading period and blooming period, which indicates that wheat in the middle jointing stage(lOd) is easier getting injured by frost.Under cold stress, the transpiration rate of winter wheat leaves descends the most in jointing stage and filling period. Consequently, the transportation of nutrition and water inside the plant is impeded, which weakens of the conduction of photosynthetic substrates. The concentration of CO2 inclines in jointing stage, but fluctuates in all other periods, meaning that the factors affect photosynthesis switches between stomatal factor and non-stomatal factor.Under cold stress, the weight and number of spikes and the weight of stem of winter wheat drop, and the total biomass drops due to the decline of photosynthetic rate. The production of winter wheat gains energy from the photosynthetic compound in the stem. For weak winter wheat, frost in the middle stage(lOd) exerts the biggest effect, while for weak spring wheat, frost in the late stage(15d) does.The factors affecting production and the soluble sugar content of winter wheat varies due to the cold stress in different periods. The soluble sugar of winter wheat ascends in the early stage during the adverse environment, and drops in later stages. Under cold stress, the quantity and velocity of photosynthetic compound transportation declines and the obstruction of the transportation of dry matter grows with the cold stress getting enhanced. So the transportation of soluble sugar among organs of the plant get hindered, manifesting as suppression of the quantity and efficiency and the decline of production in this experiment. |
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