Preliminaty Study On Sunburn Mechanism Of Korla Fragrant Pear Trunk And Its Prevention Measures During Over-wintering Period

In recent years, the winter stress harm problem of Korla fragrant pear is increasingly prominent because of the influence of the factors such as climate change and planting conditions. According to these problems, research methods such as biometeorology and plant physiology combined with stress experiment in field and experiment indoor based on review of forest and fruit trees sunburn injury at home and abroad in this project. Cambium temperature and protective enzyme activity variation characteristics of trunk north-unexposed and south-exposed were analyzed by monitoring the temperature, environmental meteorology factors, and the sunburn injury of the trunk cambium, and then the physiological characteristics of Korla fragrant pear sunburn injury were studied. In addition, different protection measures and real-time monitoring were used according to the double effects of sunburn and freezing injury. The effects of different prevention measures to safe hibernation of fragrant pear were comparative analyzed. The research results can preliminarily clarify the sunburn harm mechanism of fragrant pear hibernation, and provide the theoretical basis and scientific foundation to the harm prediction and disaster reduction management. The results also provide scientific prevention and disaster reduction scheme to fragrant pear hibernation.The main results are as follows:(1) The sunburn injury of trunk north-unexposed in overwintering period is caused by repeated heating and cooling by strong light and the decreasing of cold resistance. The possibility of sunburn and freezing injury simultaneous action in north-unexposed trunk is higher than that of in south-exposed bark.(2) The solar radiation is basic reason for the temperature of cambium layer in all different kinds of meteorological factors. The increasing of wind speed play a certain role in the stability of the cambium temperature. Tempreratrue can be taken as the characterization constant to measure the temperature level of the cambium.(3) Febrary is the most accumulative effected month of sunburn and freezing injury to korla fragrant pear trunk in Korla city. Therefore, it is necessary to take heat preservation and shading treatment to prevent sunburn in this period. (4) There is no obvious difference of SOD activity of fragrant pear trunk cambium layer between barks in north-unexposed and south-exposed, but the difference of POD and CAT activity is obvious extremely significantly. Therefore, the POD and CAT can be taken as the indexes to judge the sunburn injury.(5) The temperature is the main cause for the change of protein and proline. The content of soluble protein in fragrant pear trunk cambium layer decreased as the temperature increased, and content of proline is opposite.(6) The branch is the relatively sensitive to freezing injury during the overwintering period of fragrant pear, and the trunk cambium in south-exposed bark is the relatively insensitive. The south-exposed bark cambium is the most sensitive to joint influence of sunburn and freezing injury.(7) The order of the anti-freezing role are:straw> silver reflective film> straw rope> lime wash>ck; the order of anti-sunburn role are:straw>straw rope>-silver reflective film>lime wash>ck. The temperature difference of cambium under rice straw was the lowest, and was the best measure in anti-freezing and anti-sunburn compared to other covering measures.(8) The Light color covering measures can decrease the temperature fluctuation of cambium, advantage to reduce over-wintering damage.(9)The lower part of the bark was easily damaged by combination of low temperature and sunburn.