Which of these plants is considered to be common in an estuarine habitat?

An estuary is a partially enclosed coastal body of water where freshwater from rivers meets and mixes with saltwater from the sea. Estuarine habitats have fluctuating salinity, tidal influence, and waterlogged, often muddy substrates. Only specially adapted plants can thrive in these conditions.

Mangrove trees and shrubs are the characteristic vegetation of estuarine and coastal swamp habitats in tropical regions. They possess several key adaptations for this environment:

• Prop roots (stilt roots): Provide anchorage in soft, unstable mud and raise the plant above tidal water.
• Pneumatophores (breathing roots): Aerial roots that project above the waterlogged soil to obtain oxygen, since the anaerobic mud lacks sufficient dissolved oxygen for root respiration.
• Salt-excreting glands: Allow the plant to tolerate the high salt concentration of brackish water.
• Viviparous seeds: Seeds germinate while still attached to the parent plant, producing seedlings that can establish quickly once they drop into the water or mud.

Plantain, Gmelina, and Iroko are all terrestrial plants that grow in well-drained, non-saline soils. They lack the specialised adaptations required for survival in a saline, waterlogged estuarine environment.