Occurrence of tannins in leaves of beech trees (Fagus sylvatica) along an ecological gradient, detected by histochemical and ultrastructural analyses
Occurrence of tannins in leaves of beech trees (Fagus sylvatica) along an ecological gradient, detected by histochemical and ultrastructural analyses
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DOI：
10.1046/j.1469-8137.1998.00121.x
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发表时间：
1998-03-01
期刊：
影响因子：
9.4
通讯作者：
Tani, C
中科院分区：
文献类型：
--
作者：
Bussotti, F;Gravano, E;Tani, C
植物对环境胁迫(干旱、低养分供应、UV-B辐射、臭氧)的积极响应是植物的硬化体和酚类化合物的合成。在此，我们描述了沿生态梯度的三个地点野青冈叶片的形态和组织化学变化：从凉爽和保护条件下的地点到山脊上的地点，那里的树木生长在薄薄的土壤上，夏天暴露在风和强烈的太阳辐射下。形态数据表明，随着林分生态条件的恶化，单株叶面积减小，而叶厚度及其比干重(即单位叶面积干重)增加。组织化学和超微结构测试表明，酚类物质在一年中显着增加。这些物质主要存在于生长在胁迫条件下的树木的叶子中，已被鉴定为主要为单宁。它们聚集在液泡中，特别是上表皮层和栅栏叶肉的液泡中；在以后的阶段，它们似乎溶解在细胞质中并重新定位，最终渗透到纤维纤维中的表皮细胞的外壁，在那里它们聚集在一起，在壁面和角质层之间形成不透明电子的层。对表皮细胞的观察还显示，外层细胞壁较厚。本文讨论了次生代谢物在保护和解毒过程中的作用，以及这些变化在山毛榉生态生理中可能的生态意义。
Sclerophylly and synthesis of phenolic compounds are active responses of plants subjected to environmental stress (drought, low nutrient supply, u.v.-B radiation, ozone). Here we describe the morphological and histochemical alterations occurring in field-grown leaves of Fagus sylvatica L. from three sites located along an ecological gradient: from a site in cool and protected conditions to one located on a mountain ridge, where the trees grow on a thin layer of soil and are exposed to the wind and to intense solar radiation in summer. The morphological data show that, as the ecological conditions of the stand worsen, individual leaf surface decreases, while the thickness of the leaves and their specific d. wt (i.e. d. wt per unit leaf area) increases. Histochemical and ultrastructural tests show a marked increase of phenolics during the course of the year. These substances, present primarily in the leaves of trees growing in stress conditions, have been identified mainly as tannins. They accumulate in the vacuoles, especially those of the upper epidermal layer and the palisade mesophyll; at a later stage they appear to be solubilized in the cytoplasm and retranslocated, eventually impregnating the outer wall of the epidermal cells amidst the cellulose fibrils, where they cluster together and form an electron-opaque layer between the wall and the cuticle. Observation of the epidermal cells also reveals that the outer cell wall is thicker. The paper discusses the roles of secondary metabolites in protection and detoxification processes; the possible ecological significance of these alterations in the ecophysiology of beech trees.