| Brassica oleracea L. is an important vegetable in the world. In China, its planting area is over 340,000 hectare every year, which is the second place in foliaceous vegetable planted. With the increase of the planting area, planting in winter naturally was paid much more attention to. Temperature becomes the restrictive factor of quality and quantity because it is often exposed to low temperature during the winter. But the research of low temperature effects was seldom reported. This study was carried out on Brassica oleracea L.. According to the research of physiological and biochemical indicators or index, components of soluble proteins, substrate protein of phosphorylation and the activity of protein kinase in low-temperature stress in the leaves of Brassica oleracea L., we tried to find the law of the physiological and biochemical response of Brassica oleracea L. leaf to low temperature. At the same time, discussion on the signal transduction can also provide further evidences for revealing the mechanism of low-temperature stress. The results are showed as follows:Malondialdehyde (MDA), superoxide dismutase (SOD), ascorbate peroxidase (ASP) and peroxidase (POD) activities were changed greatly after 0~30min's treating with low temperature. When low-temperature stress lasted to 3min, MDA in the leaf of Brassica oleracea showed no obvious change. When the treatment time lasted to 5min, the first peak appeared, compared with the control, the peak reaches 104.10%. 10min later, it went down to 86.27% of the control, and then went up again. 30min later, it hit to 113.93%, which surpassed the value of the first peak. After treating with low temperature, the activities of SOD, APS and POD showed different increasement. SOD activity rose in the first 10min, and began to descend in the second 10min, and then increased again. Though in 20min, SOD activity reached the lowest level, it was still higher than that of the control. ASP activity increased slowly during 0-5min and increased sharply during 5-10min, then began to decrease slowly. When reached the lowest level after 20min, it began to increase again. During the whole process, ASP activity kept higher than that of the control. Compared with SOD and ASP, the alteration of POD activity was different. The first step was that the activity descended,and in the first 10min the activity was lower than that of the control, and then kept rising. SOD and ASP activities increased in a wide range, while POD activity increased in a narrow range. All of these have shown that SOD and ASP may play a main role during the cold resistance process, while POD acted as an assistant factor.The results suggested that Brassica oleracea can adapt to the condition of low temperature by elevating the concentration of micromolecule and macromkolecule substances such as free Pro, soluble sugar and proteins, and et al. Low-temperature stress had a obvious effect on Pro content. After 3min low temperature treatment, Pro content was 3.60 times of the control. After 5min, 23.04 times of the control, and at lOmin, the content began to descend clearly, but it still kept at 14.79 times of the control, then began to decrease, 30min later, some increasements occurred. Content of soluble sugar reached the first peak 5min later, it attained 125.00% of the control. At lOmin, it descended quickly and reached 92.68% of the control. After 20min, it increased gradually, and attained 134.52% of the control 30min later. At the beginning, soluble protein content increased quickly, 5min later, it got to 2 times of the control. It went down quickly in turn, at 15min, it reached the lowest level, but it still be 1.36 times of the control, which was much higher than that of the control, then kept rising.The change of ABA content shows a coincidence with what described above. But its first peak occurred at 3min, a little earlier than the others, and it is 2.03 time of the control. The protein kinase activity arrived at 2 times of the control at 3min, and at 5min, it decreased in a wide range. But...
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