The Institute of Low Temperature Science, Hokkaido University, Sapporo, Japan.
Plant Physiol. 1966 Feb;41(2):353-9. doi: 10.1104/pp.41.2.353.
The effect of temperature on hardening was studied at temperatures ranging from 0 degrees to -20 degrees using twigs of willow and poplar. In October and in late April when the twigs are not very frost hardy, hardening at 0 degrees produced a considerable increase in their frost hardiness, although the effectiveness of hardening at 0 degrees decreased with a decrease in the environmental temperature. In twigs which could withstand continuous freezing without injury, hardening at -3 degrees to -5 degrees was most effective in increasing the frost hardiness of the twigs. Below -20 degrees , only negligible increase was observed either in frost hardiness or sugar content.The rate of starch to sugar conversion differed remarkably in different twig tissues. The starch in xylem was more slowly converted to sugar than that in the cortex. The optimum temperature for converting starch into sugar during frost hardening was also found to be -3 degrees to -5 degrees . In addition, the greater the effectiveness of the hardening treatment, the greater the rate of conversion from starch to sugar. The frost hardiness of a twig is closely related to the sugar content of the twig, especially in the xylem.
采用柳树和杨树的嫩枝，研究了温度在 0 度至-20 度范围内对硬化的影响。在 10 月和 4 月下旬，嫩枝的抗冻能力不强时，在 0 度下硬化会显著提高它们的抗冻能力，尽管 0 度下硬化的效果随着环境温度的降低而降低。在嫩枝可以承受连续冻结而不受伤害的情况下，-3 度至-5 度的硬化处理最有效地提高了嫩枝的抗冻能力。在-20 度以下，无论是抗冻能力还是糖含量都观察到微不足道的增加。淀粉向糖的转化速率在不同的嫩枝组织中差异显著。木质部的淀粉比皮层的淀粉转化为糖的速度更慢。在抗冻硬化过程中，将淀粉转化为糖的最佳温度也被发现为-3 度至-5 度。此外，硬化处理的效果越大，从淀粉到糖的转化速率就越大。嫩枝的抗冻能力与嫩枝的糖含量密切相关，尤其是木质部。
