The word nutrition is derived from the term nutrient. Nutrient can be defined as a substance, which an organism obtains from its surroundings and uses it either as an energy source, or for biosynthesis of body constituents.

Thus, nutrition is a process of intake, as well as utilization of nutrients by an organism.

Modes of nutrition

Based on the mode of obtaining food, plants can be classified into two groups’ autotrophic plants or autotrophy and heterotrophic plants or heterotrophy. Green Plants are autotrophic (auto means self, trophy means food) or self nourishing. They are able to manufacture carbohydrates from raw inorganic materials and thus nourish themselves.


Non-green plants, on the other hand, are heterotrophic (heteros means different); that is they cannot prepare carbohydrates for their nourishment. Heterotrophy derives nutrients from different sources.

Heterotrophic nutrition can be defined as a type of nutrition in which energy is derived from the intake and digestion of the organic substances, normally of plant or animal source. The heterotrophic plants may be parasitic, saprophytic, symbiotic or insectivorous. An account of such plants having special mode of nutrition is described below.

1. Parasites

Parasite is an organism which obtains its food either partially or completely, from a living organism called host. It may live inside (end parasite) or outside (ectoparasite) the body of host. Parasitism is common among the fungi and bacteria. The fungal mycelium can enter the host either through the stomata or by dissolving cell wall of the host by secretion of certain enzymes.


Parasites differ in their host specificity. There are some parasites which can attack a number of hosts e.g. Botrytis cinerea. Others are host specific that is they attack only particular hosts. Some parasites pass different phases of their life cycle on different hosts. The phenomenon is spoken as heteroecism.