波兰的气候是变化不定的。在过去常常观测到果树在冬季的冻害,特别是经过长期温暖的气候之后,有一段时间有严重冻害。在1939—1940年和1962—1963年的冬季就观察列这类冻害。许多果树在经历严冬的翌年即干枯死亡。波兰气候条件下的果树能够获得对秋、冬和早春低温的抗性,并使之在这种危险的季节生存下来,防止发生冻害。按照Weiser氏(1970年)的理论,抗寒锻炼的过程,同昼长和光谱范围的变化一起,始于九月份。 Poland’s climate is volatile. Frozen fruit trees have often been observed in the past in the winter, especially after a long period of warm climate, there is a period of severe frost damage. In the winter of 1939-1940 and 1962-1963, such frost damage was observed. Many fruit trees die dry the following year after a hard winter. Fruit trees in Poland’s climates have low-temperature resistance to autumn, winter and early spring and have survived this dangerous season to prevent frost damage. According to Weiser’s (1970) theory, the process of cold hard work, along with changes in day length and spectral range, started in September.