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The epidermis of most leaves shows dorsoventral anatomy: the upper (adaxial) and lower (abaxial) surfaces have somewhat different construction and may serve different functions. Woody stems and some other stem structures such as potato tubers produce a secondary covering called the periderm that replaces the epidermis as the protective covering.
The skin on the potato tuber (which is an underground stem) constitutes the cork of the periderm. [30] [31] In woody plants, the epidermis of newly grown stems is replaced by the periderm later in the year. As the stems grow a layer of cells form under the epidermis, called the cork cambium, these cells produce cork cells that turn into cork.
Prickle – an extension of the cortex and epidermis that ends with a sharp point. Prostrate – growing flat on the soil surface. Rhizome – a horizontally orientated, prostrate stem with reduced scale-like leaves, normally growing under ground but also on the soil surface. Also produced by some species that grow in trees or water.
Cork cambium (pl.: cambia or cambiums) is a tissue found in many vascular plants as a part of the epidermis. It is one of the many layers of bark, between the cork and primary phloem. The cork cambium is a lateral meristem and is responsible for secondary growth that replaces the epidermis in roots and stems.
The epidermis is the outermost of the three layers that comprise the skin, the inner layers being the dermis and hypodermis. [1] The epidermis layer provides a barrier to infection from environmental pathogens [ 2 ] and regulates the amount of water released from the body into the atmosphere through transepidermal water loss .
During embryogenesis, the epidermis splits into two layers: the periderm (which is lost) and the basal layer. The basal layer is a stem cell layer and through asymmetrical divisions, becomes the source of skin cells throughout life.
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The dark horizontal lines on silver birch bark are the lenticels. [1]A lenticel is a porous tissue consisting of cells with large intercellular spaces in the periderm of the secondarily thickened organs and the bark of woody stems and roots of gymnosperms and dicotyledonous flowering plants. [2]