Some plants are incapable of photosynthesizing and obtain water, mineral and certain organic compounds from other autotrophs are called heterotrophs and the nutrition is called heterotrophic nutrition.
1. Parasitic nutrition:
Parasites obtain their nutrition from living plants or animals which are called hosts. Parasites may be obligate (total parasite) or partial (semi-parasites). (A) Obligate parasites: Without chlorophyll, take whole of their nutrition from host
i. Total stem parasite-Cuscuta ‘
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ii. Total root parasite-Orobanche, Balanophora, Raffesia.
(B) Partial parasites:
Green, manufacture their own food but depend upon other plants for minerals and water.
i. Partial stem parasite-Viscum album, Loranthus
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ii. Partial root parasite-Santalum, Thesium, Striga.
2. Saprophytic nutrition:
Saprophytes obtain their nutrition from dead and rotting organic matter e.g., Many bacteria, fungi mosses, some pteridophytes etc.
i. Neothia (Bird’s nest orchid): Grows on humus rich soil. Roots are associated with ectotrophic mycorrhiza.
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ii. Monotropa (Indian Pipe) : Grown on humus rich soil of pine forests, under ground part is associated with endotrophic mycorrhiza.
3. Symbionts:
Symbiosis is an association of dissimilar organisms to their mutual advantage e.g., Lichen (association of algae and fungi), a coralloid root of Cycas, Mycorrhiza etc.
Mycorrhiza:
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An association between a fungus and roots of higher plants. Fungus supplies the water and salts to the higher plants and in return obtain the prepared food from the green plants. Such association may be endotrophic or ecto-trophic.
4. Insectivorous plants:
Such green plants which obtain their nourishment partly from soil and atmosphere and partly by digesting nitrogen. The leaves of such plants are modified in various ways for capturing insects, e.g., Drosera. (sundew), Utricularia (bladder wort), Dionaea (venusfly trap), Pinguicula (butterwort), Nepenthes (pitcher plant), Aldrovanda (water flea trap) etc.