Question

Viscum is
(a) Partial root parasite
(b) Partial stem parasite
(c) Total root parasite
(d) Total stem parasite

Answer 1

Hint: Root is the underground non-green part of the plant which lacks leaves, nodes, and buds. It is an anchorage plant and functions for the absorption of water and mineral salt. Due to some morphological changes in the root of some plants, it shows some specialized functions also like food storage, breathing, support, etc.

Complete answer:
Most of the plants are autotrophic. However, some plants are heterotrophs and obtain their nutrition as parasites and saprotrophs. Some of the parasitic plants are Rafflesia (total root parasite), Cuscuta (total stem parasite), Viscum (partial stem parasite), Loranthus (partial stem parasite), Striga (partial root parasite) etc.

Additional Information: Modification of root for vital function also shows morphological changes like epiphytic growth on tree branches, buoyant root at the node of aquatic plant, adventitious bud, the contractile root which shrink and bring underground organ into proper depth, leaves like roots in Salvania, and root thorns.
The accessory function of the root involves the storage of food in carrots, radish, sweet potatoes, etc. Support in case of a banyan tree, corn Pandanus, etc. Climbing for support in Betal, Tecoma, Pothos, etc. Nitrogen fixation in the leguminous plant. Pneumatophores in mangrove plants and retention of moisture in hygroscopic roots of some orchids which absorb moisture directly from the air.
Thus, the correct answer is option D.

Note: Some roots are green in color which are capable of performing photosynthesis in presence of sunlight. It arises in the form of hanging thread, thalloid, and flat ribbon. In Podostemon, root produces small flowering shoots which help in reproduction.