Question

Rhizophore is characteristic of
(a) Psilotum
(b) Ophioglossum
(c) Agaricus
(d) Selaginella

Answer 1

Hint: Rhizophores, a prop like leafless structure widely noticed in climbing species of many plants for providing support to them. These plants have microphylls, which are the characteristic features of this plant.

Complete answer:
The rhizophore is an organ special to the genus Selaginella. It is usually present either on the upper or lower surface, or both, at the point of branching, of the dorsi-ventral stem. Rhizophore rapidly elongates into a root-like organ that grows downward to the soil, it emits roots close behind its apex which serves to fix the plant in the substratum. The rhizophore usually dichotomizes before reaching the soil. Studies are indicative of the fact that all species do produce rhizophores and roots are a result of the indirect method of rhizophore-formation.
So, the correct answer is ‘Selaginella’.

Additional Information: Rhizophore has a monarch structure of the stele with central protoxylem thus similar to the root of the same plant anatomically. Similar to the root, it is completely devoid of any lateral appendages in the form of foliar organs and grows downwards to the soil and performs the function of absorbing water through its tissues. It produces lateral endogenous roots. On the other hand, it resembles a stem or shoots in the fact that it arises exogenously from the tissue of the leafy shoot at the region of forking. Presently it is considered as root morphologically.

Note:
- Rhizophore is a leafless branch, which produces roots when it reaches soil.
- Rhizophore is a structure of controversial morphological nature.
- Sporophylls in Selaginella may form a distinct compact structure called strobili. Strobili are also called cones. Selaginella belongs to the class lycopsida of pteridophyte.