The periderm (from the Greek. Περι - near and the Greek. Δερμα - skin) is a complex of tissues consisting of the phellogen and its derivatives - the phalloderm (deposited inward) and felloma , or cork (secondary integumentary tissue , deposited outward). The periderm is one of the clearly expressed structural elements of the structure of the stem of higher plants, which cannot be attributed to either tissues or organs. Such elements are called anatomical and topographic zones [1] .
In stems , covering the scales of the kidneys replaces the epidermis . In the roots, it develops under the primary cortex , which dies and is discarded [2] . The periderm is found in the stems, roots, tubers and rhizomes of perennial (less often annual ) plants [3] .
Content
Education
Initially , the pellogen cells are isolated by two successive periclinal (parallel to the surface) divisions from living cells of permanent tissues. It can arise from the epidermis (stalks of apple , willow ), the subepidermal layer (stems of birch , linden , elderberry ), the deeper layers of the primary bark (stems of barberry , pine ) or the pericycle (stems of raspberry , currant , spirea and the roots of most plants), and also phloem (stalks of grapes ) [3] . Of the three formed cells, the middle one becomes a pellogen cell.
Fellogen cells also divide periclinally, externally separating Felloma cells (corks), and inside - Felloderm cells. Felloma is always more than a felloderm (it consists of only 1-3 layers). The newly formed cells of the cork are almost identical to the pellogen cells, but as new cells form, the previously formed cells are pushed to the periphery and begin to differentiate [4] .
Building
The periderm consists of a complex of tissues different in structure and function:
- fellema (cork) - secondary integumentary tissue, consists of dead cells filled with air or brown resinous or tannins . In the process of sampling , suberin is deposited on its primary membrane, and a cellulose secondary membrane is deposited on the suberin layer from the side of the cell. There are no pores in the cell walls.
- fellogen (cork cambium ) - a single-layer meristem , consists of short cells tabular in cross section.
- The phalloderm consists of living, externally similar to the cells of the phallogen cells. They usually contain spare substances that are used by the phallogen [4] .
In contrast to the exoderm of the root, the cells of which also cork, but are staggered, the cells of the entire periderm and cork in particular make up the radial rows [5] .
Since the internal tissues need oxygen , but are isolated from the atmosphere by fellas, special areas for gas exchange, lentils, are formed in the periderm [1] .
Functions
The periderm (especially the cork) performs the following functions:
- protection of internal tissues from drying out;
- water and gas impermeability;
- gas exchange through lentils [1] ;
- thermal insulation [5] .
See also
- Lentils
Notes
- ↑ 1 2 3 Timonin, 2007 , p. 105.
- ↑ Lotova, Nilova, Rudko, 2007 , p. 60–61.
- ↑ 1 2 Periderm - an article from the Great Soviet Encyclopedia .
- ↑ 1 2 Lotova, 2010 , p. 69-70.
- ↑ 1 2 Lotova, 2010 , p. 70.
Literature
- Lotova L.I. Botany: Morphology and anatomy of higher plants. - Ed. 4th, add. - M .: Book House "LIBROCOM", 2010. - 512 p. - ISBN 978-5-397-01047-4 .
- Timonin A.K. Botany: in 4 tons. Higher plants: a textbook for students. higher textbook. institutions. - Moscow: Publishing Center "Academy", 2007. - V. 3. - 352 p. - ISBN 978-5-7695-3184-2 .
- Lotova L.I., Nilova M.V., Rudko A.I. Dictionary of phytoanatomical terms: a training manual. - M .: Publishing house LCI, 2007. - 112 p. - ISBN 978-5-382-00179-1 .