Secretory tissue. Formed by living cells specialized in producing secretions that originate from cellular metabolism and that can be eliminated abroad or retained in canal cavities.
Summary
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- 1 General
- 2 Internal secretory structures
- 1 Lysigenic cavities
- 2 Schizogenic ducts and cavities
- 3 Laticiferous
- 3 Epidermal secretory structures
- 1 Glandular hairs
- 2 Hydrodes
- 3 Floral and extrafloral nectaries
- 4 Source
General
Cells, in their vital phenomena, must absorb and expel various substances, for which they constitute a specialized tissue or secretory tissue, which plays important roles in biology and plant ecology. Depending on its location in plants, the secretory tissue can be epidermal or internal.
Secretory tissues occur in primary and secondary tissues; the products they secrete are poured by the protoplasm into numerous small vacuoles and rarely completely fill the cell, which sometimes dies.
As plant secretions, they are especially widespread: mucilages, gums, gum resins, resins, essences, tannins, alkaloids, oxalate crystals, etc. The laticifers, the pockets or cavities and the glandular cells are part of the secretory tissue.
Internal secretory structures
When located in the medulla, the secretory tissues are known by the names of internal secretory tissues, and may be made up of simple cells or grouped together in the form of secretory channels, sacs or bags. Among these we have:
- Lysigenic bags or cavities.
- Schizogenic ducts and cavities.
Lysigenic cavities
They come from groups of cells loaded with secretory products, whose membranes and protoplats have been gradually destroyed. Examples of this type of cavities are the bags filled with essential oils, which appear in the leaves and fruits of oranges, lemons and other ruthaceae, as well as in many myrtaceae.
Schizogenic ducts and cavities
They are formed by the separation of glandular cells that pour their contents into the central cavity. Depending on their content, oil, resin, gum and mucilaginiferous ducts and cavities are distinguished. For example, resin canals are found in many conifers; oil ducts with essential oils in the umbelliferous; ducts with gums and mucilages in the cycads; ducts with essences and other compounds in Eucalyptus.
Laticiferous
They contain as a secretion product latex, a milky-looking aqueous liquid, almost always white, and rarely other colors (yellow), which flows from the broken tubes and coagulates quickly in the air. These tubes are often highly branched and lack transverse septa; They have a circular section and their cell wall is cellulose, smooth, elastic, and surrounds a living parietal layer with protoplasm that contains a large number of nuclei and sometimes also starch grains. We can find laticiferous tubes in euphorbiaceae (Euphorbia and Hevea), apocináceas (Nerium), among others.
Epidermal secretory structures
Glandular cells isolated or in groups often occur in the epidermis , producing and accumulating products made by the protoplasm. They have a large amount of cytoplasm, large nuclei and abundant mitochondria. Example of these cells we have:
- Glandular hairs
- Hidátodos
- Floral and extrafloral nectaries
Glandular hairs
The secreted products are essences, resins and mucilages generally, as occurs in the leaves of geranium and tobacco.
Hidátodos
They occur in many monocotyledons and dicotyledons; for example on the leaf tips, on the teeth of the leaf edge or just in front of the end of the large leaf nerves. They are groups of small parenchymal cells devoid of chlorophyll, located under special aquifer stomata, which allow the exit of liquid water (guttation).
Floral and extrafloral nectaries
They produce a sugary secretion that attracts insects and constitute surfaces or glandular hairs located, most of the time, inside the flowers (flower nectaries) and outside (extrafloral nectaries).