Some studies regarding the biology of buds and twigs in winter.
Some studies regarding the biology of buds and twigs in winter.
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DOI：
10.1086/328871
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发表时间：
1906-01-01
影响因子：
--
通讯作者：
Wiegand, KM
中科院分区：
文献类型：
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作者：
Wiegand, KM
含有相当数量分化良好的器官的芽通常由鳞片保护。那些埋在树皮里的树除了生长点或初级叶子外，通常什么也不含。芽鳞不仅是覆盖大芽的最可行的结构，而且还可以使芽膨胀，并在展开时保护幼芽。大多数树木的芽基在夏初生根，逐渐生长到深秋，一直休眠到早春，然后经过一段时间的膨胀准备展开。深色的芽通常比浅色的更温暖；但是深色和花蕾早开之间是否有关系的问题还没有确定。当温度降至零下18度时，大多数芽中都有冰。而且通常是大量的。在其他情况下，由于小细胞组织和水分含量不足，它的缺失。冰冻的树枝比正常的小。它们的收缩主要发生在树皮中。冰冻的花蕾没有那么明显地表现出这种收缩，可能是因为花蕾鳞片的形状发生了变化。芽的解冻，如果足够慢，每一度与冻结成反比，所以在组织的冰点，所有的冰都消失了。关于芽鳞的功能，几乎没有证据表明它们的功能是防止水分进入；它们作为温度调节剂对植物也不重要。芽鳞的进化可能是为了防止过度的蒸腾作用和保护脆弱的组织免受机械损伤。当花蕾打开时，鳞片通常会长出来，形成一个管状结构，保护幼芽免受过多的水分流失。像七叶树这样的芽里的毛不是用来调节温度的，而是用来保护幼芽不受蒸腾作用过大的影响。
Buds containing a considerable number of well differentiated organs are usually protected by scales. Those sunk in the bark usually contain little besides the growing point or rudimentary leaves. Bud-scales are not only the most feasible structures for covering a large bud, but they also allow the bud to swell, and protect the young shoot when unfolding. The bud fundament in most trees is laid down early in the summer, grows gradually till late autumn, remains dormant until early spring, then passes through a period of swelling preparatory to unfolding. Dark-colored buds are usually warmer within than light-colored ones; but the question whether there is any relation between dark color and the early opening of the buds was not decided. Ice may be found in most buds when the temperature has fallen as low as -18⚬C. and usually in large quantities. Its absence in other cases is due to small-celled tissues and meager water content. Frozen twigs are smaller than normal ones. Their contraction occurs mainly in the bark. Frozen buds do not show this contraction so plainly, probably because of change of form in the bud-scales. The thawing of buds, if sufficiently slow, is per degree in inverse ratio to the freezing, so that at the freezing point of the tissue all the ice will have disappeared. Regarding the function of bud-scales, there is little evidence that they function by keeping the water out; neither are they important to the plant as modifiers of temperature. Bud-scales have probably been evolved to prevent excessive transpiration and to protect the delicate tissue from mechanical injury. When the bud opens the scales often grow out, forming a tube-like structure which protects the young shoot from too great loss of water. The wool in such buds as horsechestnut is not to modify the temperature, but to protect the young shoot from too great transpiration.