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植物越冬的能力部分地取决于秋季合成以及向根和根颈运输和贮藏营养物质的能力(Smith,1964)。苜蓿要在北部地区存活越冬,它必须在秋初极早地完成其发育以便在严霜(即温度降到-2.2℃)到来之前积累营养物质(Hodgson,1964)。如果秋季刈割苜蓿,当温湿条件适宜时,贮藏的营养物质就会被用于再生生长而消耗殆尽,结果植物在冬季的伤害就有增加的趋势。因此,秋季第一次严霜平均日期前的4—6星期是苜蓿越冬的临界期(Smith,1964)。
The ability of plants to overwinter depends in part on their ability to synthesize in autumn and to transport and store nutrients to roots and roots (Smith, 1964). To survive overwintering in northern areas, alfalfa must complete its development extremely early in the fall in order to accumulate nutrients before severe frost (ie, the temperature drops to -2.2 ° C) arrives (Hodgson, 1964). If autumn mowing alfalfa, when the temperature and humidity conditions are appropriate, the stored nutrients will be used to regenerate and exhausted, the result of plant injury in the winter there is an increasing trend. Therefore, 4-6 weeks prior to the first average frost in autumn is the critical period for overwintering alfalfa (Smith, 1964).