The Saprophytic Orchids

The Saprophytes, unlike the common plants, are non-green in color and cannot prepare their own food. They derive their nutrition from decayed organic substances of vegetable or animal origin. In the undisturbed primary forests, the decaying leaf litters constitute the topsoil, which is very light and rich in nutrients. Some orchids afford to live as saprophytes in such habitats.

Habits of these saprophytic orchids are quite diverse. They are invariably leafless and usually brown, yellow or dull white in color. These are erect or climbing herbs with slender or thick, glabrous or hairy, simple or much branched sheathed stems. They mostly possess a modified subterranean stem in the form of a thick and fleshy rhizome, rootstock or an irregular-shaped corm, often with long tuberous roots. The size of the plants vary from an inconspicuous thin stem rising barely 10 cm above the ground, as in Gastrodia exilis, to thick, fleshy vines, climbing over trees to lofty heights up to 35 m (as in Erythrorchis altissima). In the climbers the stem bears distinct nodes and internodes; climbing roots and scales are borne at each node. The flowers could be minute, dull white, borne on a simple glabrous scape or large, bright yellow-colored, born on a much branched glabrous or furfuraceous panicle. Sometimes the flowers do not fully open. Corallorhiza has characteristically cleistogamous flowers. Saprophytic orchids are seen in the wild during the active period of growth for several weeks to several months in a year and go dormant after the dispersal of seeds. The aerial shoots disappear and they perennate through the specialized organs underground. Some of them like Didymoplexis pallens lead a subterranean life and emerge above the ground only during flowering when the floral shoot is sent up; its aerial shoot is reduced to a knob-like stem on the apex of the corm.

The saprophytic orchids could be true or holo-saprophytes without the green pigments (chlorophylls) in the aerial shoot. There are a few species, which possess chlorophylls in the epigeal parts; these are known as hemisaprophytes. The saprophytic orchids are incapable of developing root hairs and depend for their existence upon the mycorrhizal fungi present in their roots. They possess greater amount of mycorrhiza in their roots than the non-saprophytic orchids, as they fully depend upon the fungi for their nutrition. The mycorrhiza commonly found with the saprophytes is Hymenomycetes. It is no more a relationship of symbiosis but a matter of these orchids living of the fungi.
In India, the saprophytic orchids have been identified. They are mostly confined to the high rainfall forests of the sub-Himalayan tract of the northeastern states including North Bengal.

There are several genera like Aphyllorchis, Chamaegastrodia, Corallorhiza, Cyrtosia, Didymoplexis, Epipogium, Erythrorchis, Galeola, Gastrodia, Lecanorchis, Risleya, Stereosandra and Yoania, which are wholly saprophytic. But there are also several terrestrial genera like Crepidium, Cymbidium, Eulophia, Neottia and Odontochilus in India, which have a few saprophytic members in them.

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