What should I do if the golden pear encounters snowy weather during flowering?

When golden pear is frozen in winter and spring, the temperature generally drops below freezing point, and the water in plant cells or cells freezes, which leads to the destruction or dehydration of the internal structure of protoplasm, and the degeneration and solidification lead to the phase change of cell membrane and the destruction of membrane system structure, which leads to plant injury and even death. During the growth of pear trees, sudden cold wave and persistent low temperature weather will be encountered. The freezing degree of golden pear is related to the cooling range, the duration of low temperature and the freezing and thawing speed. If the low temperature lasts for more than a period of time or the temperature rises suddenly during thawing, it will lead to serious freezing damage. The cold resistance of golden pear is the strongest in bud stage, followed by flowering stage and the weakest in young fruit formation stage. The critical temperature of organ freezing injury in pear fruit stage is -4.2℃ ~ 2.3℃ in bud stage, -2.2℃ ~ 1.5℃ in flowering stage and-1.5℃ in young fruit stage. Flowers in bud can tolerate the low temperature of half an hour -2.3℃, and young fruits can tolerate the low temperature of half an hour-65438 0.7℃. Pear trees are in danger of freezing injury from development to flowering. During this period, the temperature below-1.5℃ can cause organ damage, and with the advance of flowering, the frost resistance will decrease.

Trend of temperature change at flowering stage

Because the early flowering and full flowering of Golden Pear in Jianzha County are both in April, the freezing injury is serious. The average temperature in April in Jianzha County is 9.6℃, and the temperature evolution trend has obvious upward characteristics, but it is not significant. The heating rate is 0.068℃/1 0 a. In recent 50 years, the average temperature in April in Jianzha County has changed greatly (table1). Except that the temperature in the 1990s was 0.7℃ lower than the average temperature, the average temperature in other decades was slightly higher than or equal to the average. Especially in recent 10 years, the temperature has increased obviously, which is 0.5℃ higher than the average over the years. The average minimum temperature in April in Jianzha county is consistent with the average temperature, showing a U-shaped change. However, the change range of the minimum temperature is greater than the average temperature, and the average of the average minimum temperature is 65438 0.98℃. After linear fitting, the trend equation is y=0.0 105x+ 1.7478, and the heating rate is 0.1℃10 a. The trend of extreme minimum temperature in April is fluctuating and rising, and the rising range is greater than the average temperature and the average minimum temperature. The trend equation is: y = 0.0487x-6. 1.2 1, that is, the increase rate of extreme minimum temperature in Jianzha county in April is 0.4℃/ 10 a, and the anomaly of extreme minimum temperature in recent April is 10. Freezing injury at flowering stage can lead to pear withering, weakened pollination activity, weak pollen activity, and abnormal fruit in flower organs due to freezing. The flowering period is most afraid of frost and frost. The probability of continuous low-temperature weather in flowering period in this county is 75%, while the climate probability of freezing injury is 36%. When the daily minimum temperature is lower than 2℃, there will be low temperature chilling injury; Low temperature freezing will occur below 0℃, and severe freezing will occur below -2℃ [1]. From 197 1 to 2020, the duration of severe freezing injury in the early flowering period of pear trees was 1 1, 14, 8, 5 and 3 d respectively, and the duration of moderate freezing injury below -2℃ was 28, 29 and 29 respectively. The duration of severe freezing injury of pear trees in full bloom was 1, 2, 3, 1, 1 d, the duration of moderate freezing injury was 3, 8, 12, 5, 3 d, and the duration of mild freezing injury was 7, 19, 63 d respectively. At the end of 1990s, the duration of severe freezing injury was only 2 days, the duration of moderate freezing injury was 3 days, 3 days, 2 days, 4 days and 1 day respectively, and the duration of mild freezing injury was 15 days, 7 days, 16 days, 15 days and 6 days respectively. It can be seen that with the end of flowering, the probability of freezing injury of pear trees is gradually decreasing [2-3]. Although the minimum temperature shows a warming trend, the frequency of extreme minimum temperature is increasing, and its change range is large, so the risk of freezing injury at flowering stage is increasing.