Explain the Process of Excretion in Plants
Excretion in Plants
Plants do not produce nitrogeneous wastes like urea and uric acid because extra amino acids and nucleotides are not formed. They produce other types of waste products, called secondary metabolites, e.g., alkaloids, tannins, aromatic oils.
The main products excreted by plants are:
- Carbon dioxide and oxygen Carbon dioxide is formed as a result of respiration. Oxygen is formed as a result of photosynthesis.
- Excess water It is excreted through stomata and the process is called transpiration.
- Excessive salts If there is a high level of salts present in water or in the soil, these usually get deposited in plants as crystals.
- Nitrogenous Waste Products. They are byproducts of general metabolism. The common ones are alkaloids, e.g., quinine, morphine, atropine.
- Organic Acids. They are metabolic intermediates. Some of them are without any other use. Rather on accumulation they may prove toxic, e.g., oxalic acid.
- Tannins. They are complex aromatic compounds which are formed as secondary metabolites.
- Latex. It is an emulsion of varied composition which is exereted by special tubular cells called laticifers.
- Resins. They are oxidation products of aromatic oils.
- Gums. They are degradation products of cell wall.
Read More: Excretion in Animals and Human Body
Mechanism of Excretion in Plante:
Plants do not have any mechanism to collect, transport and throw out their waste products. They have adopted varied strategies to protect their living cell from waste products.
- Old Leaves. Waste products are stored in older leaves which soon fall off.
- Old Xylem. Resins, gums, tannins and other waste products are deposited in the old xyem which soon becomes nonfunctional e.g. Hard wood.
- Bark. Bark consists of dead cells which is peeled off periodically. Tannins and other wastes are deposited in the bark. Incidentally, tannins are raw material for dyes and inks.
- Central Vacuole. Most plant waste products are stored in central vacuole of their cells. They are unable to influence the working of cytoplasm due to presence of a selectively permeable membrane called tonoplast.
- Root Excretion. Some waste substances are actually excreted by the plants in the region of their roots.
- Detoxification. The toxi oxalic acid is detoxified by formation of calcium oxalate which gets crystallized into needles (raphides), prism (prismatic crystals), stars (sphaeraphides) and crystal sand. Excess of calcium is also precipitated as calcium carbonate crystals, e.g. cystolith.
- Salt Glands. They excrete excess salts obtained from the habitat.