NUTRITION IN PLANTS | Autotrophic nutrition |

NUTRITION IN PLANTS

Autotrophic nutrition

The mode of nutrition in which the organisms can synthesize their food form inorganic salts is called autotrophic nutrition. The autotrophic organisms can exist in an exclusively inorganic environment. They synthesize their food in the form sugars, lipids and proteins from CO₂ and water.

Mineral nutrition in Plants

The carbon, oxygen and hydrogen are predominant elements of the plants. The plants obtain these elements from CO₂ and water. There are many other mineral elements present in the composition of plants. These are;

1. Nitrogen: It is present in protein,

2. Phosphorus: It is present in ATP, nucleic acids and many other compounds

3. Magnesium: It is present in chlorophyll.

4. Iron: Iron is present in Cytochromes.

Source of mineral elements

Soil is the main source of these nutrients. These nutrients are essential for the growth and life of the plant. If crops are grown repeatedly on the same field, these crops cannot flourish. Soil must be replenished with these nutrients. The farmers use animal manure, sewage sludge or artificial fertilizers for this replenishment. These materials are used in measured quantities in the fields. Some chemical fertilizers used in commonly Pakistan are:

➤ Urea

➤ Super phosphate

➤ Ammonium nitrate

Mineral element deficiencies

It is difficult to determine the effects of individual minerals in both plants and animals. However, the deficiencies of some elements cause serious diseases. These diseases show clear symptoms.

1. If there is deficiency of nitrogen in soil, the growth of the plant is stunted. The deficiency of nitrogen also causes chlorosis mostly in older leaves. The lack of chlorophylls in the leaves is called chlorosis.

2. The deficiency of phosphorus causes stunted growth of roots.

3. The colour of leaf margins becomes yellow and brown due to deficiency of potassium in soil, It may cause early death of the plant.

4. The deficiency of magnesium causes chlorosis.

  Therefore, the deficiency of minerals causes many important plant diseases. These diseases have been catalogued with the. help of colour, photography. The catalogues help us to diagnose these diseases rapidly.

Heterotrophic and special mode of nutrition in plants

The plants generally obtain their food from the air or water. However, there are following special methods of nutrition.

Saprophytic Nutrition

The feeding on dead and decaying matter is called saprophytic nutrition. This decaying matter includes dead leaves in the soil and rotting tree trunks.

1. The saprophytic plants produce extracellular enzymes. These enzymes digest and decay the matter. Then the plants absorb the soluble products into their cells.

2. Some bacteria break down the proteins of dead plants and animals. They release nitrates. The roots of the plants absorb these nitrates. The plants synthesize new amino acids and proteins form these nitrates. So they play a role in the nitrogen cycle.

Parasitic nutrition

The feeding by living in or on other organisms belonging to different species is called parasitic nutrition. The parasites attach with the living hosts. The parasites penetrate their suckers into the conducting tissues of the host and absorb food. Puccinia is a parasitic fungus. It destroys the wheat plant. Dodder (Cuscuta) is a leafless plant. It lives as a twining parasite.

Symbiotic Nutrition

It is a mutual nutrition between the organisms belonging to different species, living in association with one another. Some important examples are lichens, mycorrhizae and root nodules.

1. Lichens: The association between fungus and algae cells is called lichens. The algae make food for photosynthesis. The fungus supplies water and minerals. It also protects algae from desiccation. 

2. Mycorrhizae: The association between the fungus and roots of higher plants is called mycorrhizae. The fungus depends on the photosynthate of plant. The benefit derived by mycorrhiza plant is not

properly understood. However, the plants with mycorrhiza association show better growth than without this association. Possibly, the fungus decomposes the organic material in the soil for the plants. It also provides water and minerals like phosphorus to plant.

3. Root nodules: The leguminous plants develop nodules on their roots. These nodules contain nitrogen fixing bacteria. The bacteria live on the plant material and fix atmospheric nitrogen. They convert this nitrogen into nitrates. These nitrates are used by the plants.

Nutrition in insectivorous plants

There are a few plants which supplement. Their inorganic food with organic compounds. These organic compounds are obtained by trapping and digesting insects and small animals. All the insectivorous plants are true autotrophs. But they grow rapidly when they capture prey. The nitrogenous compounds of the animal bodies benefit these plants. In some plants, these

trapped insects are decomposed by bacteria. In other plants the leaves secrete enzymes. These enzymes digest the trapped insects and release nitrogencus cor pounds. The plant absorbs these nitrogenous compounds.