Q.32 Which of the following plant has rhizophore?
Selaginella has rhizophore. This unique leafless, cylindrical organ (organ sui generis) arises exogenously at stem branching points in climbing Selaginella species, growing downward to produce adventitious roots upon soil contact, distinct from true roots or stems anatomically and morphologically.
Option Analysis
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(1) Marsilea: Heterosporous fern (Marsileaceae) with four-leaf clover-like fronds; possesses true roots from rhizome nodes, no rhizophore.
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(2) Selaginella: Correct—Rhizophore emerges at shoot forks, bears roots at tip; debated as root/stem hybrid but unique to genus (e.g., S. moellendorffii, S. kraussiana).
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(3) Equisetum: Horsetails (Equisetaceae); jointed stems with whorled branches, true rhizomatous roots—no rhizophore structure.
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(4) Rhynia: Extinct rhyniophyte (Silurian-Devonian); simple dichotomously branching axes with terminal sporangia, lacks vascular root/rhizophore differentiation.
Answer: (2) Selaginella.
Introduction to Rhizophore Structure
Which of the following plant has rhizophore? Selaginella features this distinctive leafless cylindrical structure arising at stem dichotomies, growing geotropically downward to anchor and produce adventitious roots—considered neither true root nor stem (organ sui generis).
Selaginella Rhizophore Anatomy
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Origin: Exogenous from shoot fork angle
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Structure: Monarch stele (central protoxylem), no leaves/scale
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Function: Root production upon soil contact; dichotomously branches
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Meristem: Superficial apical cell → internal root cap initial
Comparative Analysis
| Plant | Root Type | Rhizophore Present? |
|---|---|---|
| Marsilea | True rhizome roots | No |
| Selaginella | Adventitious + rhizophore | Yes |
| Equisetum | Rhizomatous | No |
| Rhynia | Basal rhizoids | No |
GATE Plant Diversity Application
Tests pteridophyte specializations: Selaginella = rhizophore, Psilotum = rhizome, Lycopodium = dichotomies. Critical for evolutionary morphology, organ sui generis concepts.
