Sep 27, 2014

Excretion in Plants

The excretory substances produced by plants are oxygen, carbon-dioxide, water, and some other waste materials.

Oxygen: It is a product of photosynthesis and given out of the plants.

Carbon dioxide: It is a product of respiration. Carbon is used during photosynthesis at daytime and given out of the plant during night.

Water: It is a product of respiration and photosynthesis. Water is lost through transpiration or it may be used for maintaining the turgidity in the cell.

Crystal formation: Many mineral salts, taken up as ions, may accumulate. Organic acids, which might prove harmful to plants, can be safely stored in the vacuoles of plant cells, e.g. calcium oxalate.

Elimination of wastes through leaves: In leaves certain inorganic and organic wastes are stored. The leaves fall off during autumn. The leaves and stalk of some plants e.g. blue bell die off leaving the bulb underground. The falling of yellow leaves in autumn is the seasonal time for the plants to get rid of the accumulated wastes, so the leaves are called excretophore. The change in color of the leaves is due to pigmented compound and many toxic materials such as heavy metals, and not due to removal of chlorophyll.

Storage of wastes in wood: Many organic waste products of plants are stored within dead permanent tissues such as the “heartwood”. In ebony very black wood is produced in the centre which stores chemicals in the old xylem which is no longer used for water transports.

Secretion of wastes into the soil: Some plants secrete waste compounds into the soil, occasionally using them as chemical weapon against other competing plants e.g. conifers.

Elimination through other parts: Substances are not only eliminated through leaf but also through petals, fruits and seeds.

In aquatic plants: These plants dispose of most of metabolic wastes by diffusion directly into the water surrounding them.

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