Excrition in Plants:
The removal of all harmful substances produced in the metabolic processes, from the body of plant is called excrition.
In plants the rate of catabolic processes is slow and waste products are produced in less amount. These products are not accumulated in plant body, they are used again in their anabolic processes.
In plants the nitrogenous waste products are also used in the chemical processes, they are not removed from the body.
Mostly carbohydrates are used in metabolic processes, so CO2 and water are produced. These products are not very harmful.
The substances which are produced in excess amount are:
- Water
- Co2 and O2
- Ions
(A) Removal of Water
Extra amount of water is removed from the body of plant by two methods:
(i) Transpiration:
When extra amount of water is removed from the body of plant in the form of vapours is called transpiration. Mostly transpiration takes place through stomata of leaves.
(ii) Guttation:
When water is removed from plant body in the forms of small drops, the process is called guttation. Guttation occurs by special openings, called hydathodes. These are openings without guard cells present on the tip or margin of leaves.
Guttation takes places in those plants which grow in tropical rain forests, where rate of absorption is high because there is high rain fall and due to humidity in air, the rate of transpiration is low.
(B) Release of Oxygen (O2) and Carbondioxide (Co2)
In the presence of sunlight the plants use CO2 for photosynthesis and release O2 but in the absence of light there is no photosynthesis and during respiration the plants use O2 and release CO2.
(C) Ions:
In the body of plants the excess amont of ions are combined with organic compounds, then they are deposited in dead cells of the body such as heartwood and bard or sometimes in order cells of the body.
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