Question

Rhizophore in Selaginella is
 A. A modified stem
 B. A root
 C. A shoot
 D. Organ Sui generis

Answer 1

Hint: Rhizophore present in Selaginella is an intermediate structure between root and shoot. It is the most distinctive feature of Selaginella. It is a leafless structure.

Complete answer:
Selaginella is the only living genus of the order Selaginellales, commonly called ‘Spike Moss’. Plant body of Selaginella is divided into roots, stem and leaves. Besides that some species also have rhizophore. Rhizophore (Greek rhiza = root; phora= bearer) is a leafless, cylindrical structure arising from the stem branching. It gives rise to root means. The cross-section of rhizophore shows a wide pith and many bundles surrounded by fibre strands. Rhizophore are mostly found in clambering plant species. On the basis of its morphology, the rhizophore is considered to be a root, but occasionally it gives rise to leafy branches if the leafy branches are cut off. So the feature rhizophore in Selaginella has been in controversy whether it is root or a stem. Scientists researched it and found out that it is neither root nor a stem in fact an intermediate part between root and stem. According to Goebel (1905), it was said that the organ rhizophore is neither a root nor a shoot. The term organ sui generis is latin phrase which means unique. When we study the anatomy of the plant Selaginella it is shown that rhizophore is a unique and different structure as compared to root and stem although it presents on the branch opening of stem and gives rise to root.

So the correct answer is (D) Organ Sui generis.

Note: Rhizophore is an individual structure in Selaginella which is known as Organ Sui generis which means it is an intermediate part between root and shoot. According to a biologist named J.C.Shoute, Organs sui generis has not been arisen by the result of metamorphosis. So this is also a reason because of that we consider rhizophore as Organ sui generis.