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单词	periderm
释义	periderm /ˈpɛrɪdəːm / noun [mass noun] Botany The corky outer layer of a plant stem formed in secondary thickening or as a response to injury or infection.They were observed 6-7 layers below the suberized periderm and in the tuber portion far from the buds.... The stage IV stem illustrated here shows an outer covering of periderm with fine strips of fibres formed from the secondary phloem. They are well known to occur in plant/atmosphere interfaces where they form water-tight barriers such as the leaf cuticle and suberized periderm. Derivatives peridermal /pɛrɪˈdəːm(ə)l/ adjective ... We will not address any air spaces derived from phellogen (cork cambium) as peridermal or secondary aerenchyma although it is very important for some plants, especially woody plants with secondary growth of roots. This is supported by the formation of soil/root air gaps as roots shrink in drying soil reducing root to soil contact, by formation of cortical lacunae in the roots and by peridermal dehydration. The simple ectodermal epithelium of the anterior metatarsal region produces the suprabasal peridermal layer around 6 days of development. Origin Mid 19th century: from peri- 'around' + Greek derma 'skin'.
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