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幼树受冻主要有以下四种类型:①晚秋、初冬的冻害。秋季正是果树由生长期过渡到休眠期的季节,如果叶片养分未能回流或组织不充实,当遇到秋季过早低温时,往往造成冻害。②深冬季的冻害。当冬季最低温度超过果树在自然条件下经过锻炼所获得的耐寒力时,往往引起冻害,且低温持续时间越长,冻害越重。而进入休眠后木质部和髓部的抗寒力最弱,所以表现为枝条的木质部和髓部受冻变成黑褐色,重者树干纵裂。③早春的冻害。当早春气温回升快时,地上部的水份蒸腾随气温的上升而转旺,而此时土壤尚未完全解冻,根系不能及时补充水分,加之
There are four main types of sapling frost damage: ① late autumn, early winter frost damage. Autumn is the fruit tree transition from the growth period to the dormant season, if the leaf nutrients can not return or the organization is not full, when the fall premature low temperature, often resulting in frost damage. ② deep winter frost damage. When the winter minimum temperature exceeds the cold hardiness obtained by the fruit trees after training under natural conditions, it often causes frost damage, and the longer the low temperature duration, the heavier the frost damage. After entering dormancy, the cold resistance of the xylem and pith was the weakest, so the xylem and myeloid of the branches showed cold brownish brown, and the trunk of the severed trunk was longitudinal. ③ frost damage in early spring. Early spring air temperature rise quickly, the upper part of the water transpiration with the temperature rise and prosperous, but at this time the soil has not been fully thawed, the root can not replenish the water, coupled with