Question

Explain heterotrophic mode of nutrition.

Answer 1

Heterotrophic mode of nutrition :
Heterotrophic plants do not possess chlorophyll. Therefore, they cannot produce their own food by the process of photosynthesis. Heterotrophic plants obtain food from other plants or animals by following either a parasitic, saprophytic or symbiotic mode.
a) Parasitic mode:
The organisms which exhibit parasitic mode of nutrition are called as parasites. Parasites obtain their nourishment from other living organisms. In parasitic mode of nutrition, plants depend on other plants or animals for their nourishment. Such plants are called as parasites and the ones on which parasites depend are called as hosts.
e.g.Mistletoe is a parasitic plant which depends on other organisms for its nourishment.
e.g.Cuscuta is a parasitic plant which develops special roots called haustoria. Haustoria penetrate deep into host plant tissues and just absorb the nutrients from them.
b) Insectivorous mode:
These are the plants with special leaves that are modified into special structures. These structures have the ability to trap other organisms.
e.g. Nepenthes, called as pitcher plant has its leaves modified into pitchers closed with leaves. These have a network of fibres which entangle the trapped organism and later digest it by secreting some hydrolysing enzymes to digest them.
e.g. Venus fly trap feeds on small animals and insects to obtain their nourishment. These plants especially obtain the nitrogen they require from insects and small animals.
c) Saprophytic mode:
The plants which exhibit saprotrophic mode of nutrition are called as saprotrophs. Saprotrophs are the plants that obtain their nutrition from dead and decaying organic matter. These plants secrete digestive juices onto dead and decaying matter to dissolve it and then absorb nutrients from it.
e.g. Indian pipe which is found on dead and rotting material, inhabits fungus in its roots. These extend their mycelium and secrete enzymes to digest the decaying matter.
e.g. Coral roots are another type of plants exhibiting saprophytic nutrition.
d) Symbiotic mode:
Symbiosis is the phenomenon by which two organisms maintain relationship with each other to be mutually benefitted. In symbiotic mode, organisms develop a special relationship with certain other organisms to obtain nourishment. Organisms involved in this type of relationship are called as symbionts.
e.g. Rhizobium bacteria and Leguminous plants are symbionts exhibiting symbiosis. Plants cannot utilise atmospheric nitrogen directly. Hence, leguminous plants establish a symbiotic relationship with bacteria like Rhizobium. Both the organisms of symbiotic relationship are mutually benefited. Leguminous plants provide shelter and nourishment for the bacteria and in turn bacteria fix atmospheric nitrogen to the plant.