Mode of Nutrition in Plants

Nutrition is plants is classified into two main categories: autotrophic and heterotrophic. Heterotrophic plants are further classified into saprophytes, parasite and insectivores.

Autotrophic Nutrition

It is a type of nutrition in which the living organisms manufacture their own organic food from simple inorganic raw materials. The green plants exhibit autotrophic mode of nutrition and hence called the autotrophs.

The autotrophs require external energy source for the manufacture of organic substances. Green plants obtain energy from sunlight and therefore are called photoautotrophs. The process of synthesizing food in plant in the presence of sunlight is called photosynthesis.

The insectivores are autotrophic but they develop specific structures to trap insects to overcome N2 deficiency because they grow in soils having acute N2-deficiency.

Heterotrophic Nutrition

Certain non green organisms like fungi and many bacteria fail to synthesize their own organic nutrients from inorganic substances. These organisms are thus dependent on some other external sources for their organic nutrition. Such plants are called heterotrophic plants and the mode of nutrition is called heterotrophic nutrition.

The heterotrophic plants are broadly categorised into two main groups depending upon the source from which they get their nourishment. Saprophytes, and parasites.

Saprophytes are those plants which grow and live on dead organic matter including animal and plant remains. Most of these plants secrete some extracellular enzymes which break down the complex organic compounds into simple forms. The simple form are then absorbed by the plants. Saprophytes include mainly fungi and bacteria. Among higher plants the Indian pipe plant Monotropa found in khasi hills is a saprophyte.

Parasitic Plants: Dodder (Cuscuta) known is a parasitic plant that lacks both chlorophyll and leaves. It is a yellow colour climber that attaches itself to the host. It gives out haustoria or the suckers that get attached to the phloem of the host and derive nutrition. Cuscuta does not have roots in the mature condition. It produces bunches of whitish or yellowish bell shaped flowers.

Insectivorous Plants

These are plants which are autotrophic but develop adaptations to trap insects in order to supplement the deficiency of Nitrogen in the soil. They feed on insects. They are generally found in nitrogen deficient habitats and hence to compensate the loss, they use insects as a source of nitrogen. Examples:

  • Pitcher plant: Nepenthes
  • Sundew: Drosera
  • Venus flytrap: Dionaea
  • Bladderwort: Utricularia