科研之友
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摘要
Periderm is a secondary protective tissue of woody plant organs. It consists of meristematic phellogen, and its derivatives i.e. phellem and phelloderm. The first periderm sometimes can function over the lifespan of a tree. However, in the majority of tree species, it is replaced by a rhytidome composed of successive periderm layers and dead cells of secondary phloem. Two types of phellem cells, which are thin and thick-walled, are usually distinguished. Their cell walls are overlained by suberin and wax extractive layers. Such a structure of phellem cell walls reduces the permeability of walls and leakage of water in woody plants. However, in some species, the phelloid cell, which cell walls are not suberized, may occur between typical phellem. Due to the arrangement of phellem cells and the structure of their cell walls it is possible to distinguish the annual increments of secondary protective tissues. The phellogen, as the meristematic tissue, takes part in the production of special structures such as lenticels and winged cork. The lenticels are regions with relatively loosely arranged cells characterized by suberized or non-suberized cell walls, and due to their structure the lenticels are suitable for gas exchange. The winged cork can be formed by phellogen which produces the periderm covering the surface of the stem or by independent phellogen developing prior to the formation of circumferential periderm. Additionally, the periderm (in particular the phellem) has an economic importance and it is used to production of tannins, medications, bottle stoppers as well as building or insulation materials.
- 出版日期2014-3
