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  Biology (NTSE/Olympiad)  

4. Excretion

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.
(i) Nitrogenous Waste Products.
They are byproducts of general metabolism. The common ones are alkaloids, e.g., quinine, morphine, atropine.
(ii) 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.
(iii) Tannins. They are complex aromatic compounds which are formed as secondary metabolites.
(iv) Latex. It is an emulsion of varied composition which is exereted by special tubular cells called laticifers.
(v) Resins. They are oxidation products of aromatic oils.
(vi) Gums. They are degradation products of cell wall.

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