Introduction to excretion in plants
Excretion is the process of elimination of waste materials from the body. Excretion in plants is much simpler than that of animals and as such it does not pose any serious problem in plants. There are several reasons for this:-
1. The rate of catabolism is comparatively much slower in plants than in animals having the same body weight and consequently the rate of accumulation of body waste is much slower.
Introduction to excretion in plants
Excretion is the process of elimination of waste materials from the body. Excretion in plants is much simpler than that of animals and as such it does not pose any serious problem in plants. There are several reasons for this:-
1. The rate of catabolism is comparatively much slower in plants than in animals having the same body weight and consequently the rate of accumulation of body waste is much slower.
2. Plants use much of the waste products of catabolism in their anabolic process. Water and CO2 produced during respiration are utilized by green plants in photosynthesis. NH4 formed by breakdown of protein and other nitrogenous compounds are utilized by plants for synthesis of new proteins.
3. In plants metabolism is mainly based on carbohydrates than proteins and the end products of carbohydrate metabolism are far less poisonous than protein, the excretory needs of plants are, thus, reduced.
In plants no definite excretory system or organ is present for removal of wastes. The excretory products which are easily diffusible are removed by way of diffusion or osmosis. In higher plants waste materials are deposited in various parts of the body, which are later eliminated.
METHODS OF EXCRETION IN PLANTS
Leaf fall: Deciduous plants like tobacco, tea, belladona, get rid of excretory substances stored within leaf, through leaf fall.
Shedding of bark:Trees having secondary growth, shed the bark at irregular intervals, where excretory substances are stored like in Rauvolfia.
Fruit fall: Excretory substances are stored within seeds and pericarp of fruits, which are eliminated from the plant body along with fruit fall. Examples are Datura, banana, papaya etc.
Shedding of flowers:Excretory materials are stored within the flower bracts (Artemisia), sepal and petals (Santonine) are removed along with shedding of flowers.
Diffusion:Gaseous excretory materials like CO2, ethylene are excreted out by diffusion through stomata, lenticles etc.
Storage: Excretory materials like gum, resin latex, are stored within specialized cells.
Leaching:Leaching is a process of diffusion of water soluble substances like salts, hormones, inhibitors etc from underground parts of plants body to the soil.
EXCRETORY PRODUCTS OF PLANTS
Organic acids:Organic acids like citric acid in lemon, tartaric acid in tamarind, are formed as a by product of respiration. Organic acids are abundant in leaves and fruits.
Gums:Gums are formed by decomposition of cellulose of cell wall. Gum arabic, balsam are common examples.
Resin:Resins are nonvolatile substances probably formed by oxidation of essential oils. Pure resin are hard and brittle like shellac, lacquer.
Latex: Latex is an emulsion of proteins, gum, resins etc. It is a milky fluid secreted by cells or vessels in which it is present. Latex is chief commercial source of rubber.
Essential oils:These are volatile oils present in fruits, flowers etc like sandalwood oil, citrus oil, lavender oil.
Alkaloids: These are nitrogenous waste products formed in certain plant cells. Common alkaloids include quinine, nicotine, morphine, caffeine, cocaine, atropine etc.
Tannin is a type of bitter waste material used for tanning of leather, for preparing ink etc.
Glycosides are decomposition products of carbohydrates. Digitoxin, a glycoside is used for preparing digitalis.