EXCRETION IN PLANTS
Plants are much less active than animal and produce waste product at a much slower rate. They have no need of specialized excretory organ. Plant waste product include water carbon (iv) amino, acid, mucilage, alkaloid, latex, resin, crystal of salt, oil and anthocyanin. The main excretory organ of flowering plants is the stomata in the leaves and lenticels in the stem.
These are pores in the epidermis bounded by specialized epidermal cell known as guard cell. Stomata are usually found on the aerial part of the stem and leaves and on flower parts. They may be irregularly scattered or arranged in parallel rows. The guard cells are bean- shaped and fit together with the pore between them. The size of the pore alters according to how turgid the guard cell is which in turn depends on the osmotic pressure with the guard cell. When the pressure is low, the guard cells are flabby and the stoma is closed. When it is high, the guard cells are swollen and the stoma opens.
The lenticels are structurally differentiated part of the periderm which stand out because of the loose cell arrangement. In a stem undergoing secondary thickening the first lenticel usually arise beneath the stomata in the epidermis
Carbon (iv) oxide and oxygen are excreted by diffusion through stomata or lenticels: water is excreted by diffusion out of the stomata or lenticels through the process of GUTTATION OR TRANSPIRATION.
Oil and resin: these are stored in the cell of the cytoplasm where they are kept in the system until they are eliminated latex is stored in tube like system in tissue and are kept harmless until they ooze out the plant when the plant is damaged.
Tannins, mucilage, gum crystals, alkaloid, anthocyanin, calcium oxalate and calcium carbonate. These pigment are converted into resoluble compounds are deposited in dead tissue like the bark of stem and leaves and petals which are shed periodically.
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