# Explain how the adaptations of mangrove trees allow them to survive in waterlogged, saline soils.

> IB DP Biology Standard Level (2023 syllabus) — B4.1 Adaptation to environment · Explain · 4 marks

> Mangrove trees grow in coastal intertidal zones where soils are waterlogged, low in oxygen, and have high salt concentrations. Despite these extreme conditions, mangroves are highly productive and form dense forests along tropical and subtropical coastlines.

## Mark scheme (4 marks)

1. Prop roots / pneumatophores (aerial roots) project above the waterlogged sediment to allow gas exchange / uptake of oxygen for aerobic respiration
2. Salt glands in leaves actively excrete excess salt / some species exclude salt at the root by ultrafiltration, preventing toxic accumulation in cells
3. Low water potential inside root cells (due to accumulation of compatible solutes / salt exclusion mechanisms) allows osmotic uptake of water from saline soil
4. Thick, waxy / succulent leaves reduce water loss by transpiration, conserving water in an environment where osmotic stress makes water uptake difficult

## Related

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