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.
THANKYOU,