RAS question
Rhizophora species of mangroves are distinctive because of their:
Correct answer: (A) Prominent stilt roots (prop roots) extending from trunk to water.
Rhizophora mangroves are distinctive for their prominent stilt or prop roots, which arch from the trunk and branches into soft, tidal sediment.
Explanation
Rhizophora, commonly represented by red mangroves, are identified by their conspicuous stilt-like prop roots. National Park Service - Biscayne National Park describes red mangrove as appearing to walk on water because its prop roots spread outward towards the sea and form dense thickets. The MCQ's correct option is therefore the roots extending from the trunk and branches, helping anchor the tree in soft sediment and giving stability in tidal zones. Red mangrove seeds, called propagules, germinate on the tree before later floating and anchoring along the shore. The diagnostic feature being tested, however, is the visible prop-root system, not merely seed behaviour.
Why the other options are wrong
- (B) Rhizophora does not have hidden or entirely submerged roots; its stilt-like prop roots are visibly spread from the tree towards the water.
- (C) The described Rhizophora feature is a prop-root system in tidal mangrove habitat, not buttress roots of the kind associated with many terrestrial tropical trees.
- (D) Upward-pointing pneumatophores are characteristic of black mangrove, Avicennia, whereas Rhizophora is marked by stilt-like prop roots.
Concept
This tests mangrove adaptations, especially root forms used to survive unstable, waterlogged tidal habitats. It recurs in RAS Environment and Ecology because species-level examples such as Rhizophora and Avicennia are common ways to test ecological adaptation, not just definitions.