The leaves of «moderately hardy» (spinach), «very hardy» (ivy) and «extremely hardy» (spruce) plants [classification according to Levitt {1980)] show characteristic differences with respect to changes in membrane lipid composition and chloroplast ultrastructure which are correlated with the degree of the frost resistance achieved by each type of tissue during adaptation to sub-zero temperatures. Spinach leaves showed no increase in their total lipid content upon frost hardening. On the contrary, the amount of galactolipids decreased considerably, whereas that of phospholipids only slightly increased. No shift from the saturated palmitic acid to the three-fold unsaturated linolenic acid was observed. The membrane lipid content of ivy leaves and spruce needles increased to a similar extent during frost hardening. However, in contrast to spruce needles, a distinct preferential accumulation of the phospholipids was observed in ivy leaves, resulting in an increased PL/GL ratio. A considerable shift from saturated (palmitic) to unsaturated fatty acids was detected in both plants, due mainly to an increase in the proportion of linoleic acid in ivy and of linolenic acid in spruce. In spite of the considerable increase in lipid content, no increase in chloroplast number per cell could be detected in ivy leaves, although the length of the thylakoids was nearly doubled and the plastids appeared to be in a division stage: however, no real division could ever be observed. On the contrary, an increase in the number of chloroplasts and mitochondria was observed in spruce needles. Membrane augmentation became further evident by the many large invaginations of the chloroplast envelope formed when the frost-hardened leaves of ivy or spruce were exposed to sub-zero temperatures which they could just survive.

译文

:“中等硬度”(菠菜),“极度坚硬”(ivy)和“极度坚硬”(云杉)植物的叶子[根据Levitt(1980)分类)在膜脂成分和叶绿体变化方面表现出特征差异超微结构,与适应零度以下温度时每种组织的抗冻性程度有关。霜冻硬化后,菠菜叶的总脂质含量没有增加。相反,半乳糖脂的量显着减少,而磷脂的量仅略有增加。没有观察到从饱和的棕榈酸到三倍的不饱和亚麻酸的转变。在霜冻硬化过程中,常春藤叶和云杉针的膜脂含量增加了相似的程度。然而,与云杉针头相反,在常春藤叶中观察到磷脂的明显优先积累,从而导致PL / GL比增加。在这两种植物中均检测到从饱和(棕榈酸)到不饱和脂肪酸的显着变化,这主要是由于常春藤中亚油酸和云杉中亚麻酸的比例增加。尽管脂质含量显着增加,但常春藤叶中未检测到每细胞的叶绿体数量增加,尽管类囊体的长度几乎增加了一倍,质体似乎处于分裂阶段:但是,不能进行真正的分裂曾经被观察到。相反,在云杉针头中观察到叶绿体和线粒体数量增加。当常春藤或云杉的冻干叶子暴露于零度以下的温度下就可以生存时,叶绿体包膜的许多大的浸入使膜的增强变得更加明显。

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