Monday, February 29, 2016


You have learnt that a variety of end products are formed during metabolism and of these nitrogenous wastes are important.
Plants do not have any specific organ to excrete these wastes. As in animals, carbon dioxide, water, ammonia and other nitrogenous wastes are also formed in plants.
In the plants, carbon dioxide released during respiration is sent out through stomata of leaves. Due to this, the heat in the plant body is reduced.

 Even when leaves are absent, as in the germinating seeds. Carbon dioxide formed during respiration is released into the atmosphere. Plants have the capacity to utilize the by-products of one metabolic activity as raw materials for another metabolic activity.

oxygen released during photosynthesis is utilized for respiration. Carbon dioxide released during respiration is utilized for photosynthesis. Plants can convert nitrogen and ammonia into nitrates. However, several compounds are synthesized by the plants for their own use, especially for defence.

 As plants are sessile(do not have the capacity to move), they cannot defend from the predators by running away.
 Majority of plants do not have organs for protection against the herbivores. Hence, several plants prepare chemicals and store them in roots, leaves, seeds and even in stem.

Most of these chemicals are unpleasant to taste and hence herbivores usually do not prefer to eat such plants. Some of the chemicals are toxic and may even kill the animal that eats them.

 Some of the plants secrete chemicals when injured. These chemicals  seal the wound and help the plant to recover from the injury.

Though plants produce these chemicals for their use, man has found other uses for these chemicals and benefited immensely from these chemicals.

 Some of the plants release attractants for other Organisms which will help the plant in pollination, seed dispersal or even in their nutrition.
For example, plants having root nodules, secrete chemicals to attract rhizobia in to the surroundings of the roots and form a symbiotic relationship with the rhizobium. These compounds are called secondary metabolites.

The biochemical substances produced in plants are of two types-primary metabolites and secondary metabolites, Food materials like carbohydrates, fats and proteins are the primary metabolites.

Alkaloids, Tannins, Resins, Gums, Latex etc., are some of the secondary metabolites in plants.

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