Mangroves’ Cells Help Plants Survive in Saltwater

Syllabus: GS3/Environment

Context

• A new study published in Current Biology explains the cellular adaptations that enable mangrove species to tolerate extreme salt stress, offering insights for developing salt-tolerant crops in the future.

Key Highlights of the Study

• Key cellular traits (not stomata-based): Mangroves do not rely on smaller or more numerous stomata to increase photosynthesis.
  • Instead, they exhibit: unusually small leaf epidermal pavement cells and thicker cell walls, which together give them more mechanical strength to tolerate low osmotic potentials.
• Salt management strategies
  • Salt exclusion: Some mangroves have waxy root layers that filter out salt before water enters the plant.
  • Salt secretion: Other species absorb salt but secrete it through specialised leaf tissues.

Mangroves

• A mangrove is a small tree or shrub that grows along coastlines, taking root in salty sediments, often underwater. 
• Mangroves are flowering trees, belonging to the families Rhizophoraceae, Acanthaceae, Lythraceae, Combretaceae, and Arecaceae.
• Features:
  • Saline Environment: A speciality of mangroves is that they can survive under extreme hostile environments such as high salt and low oxygen conditions.
    • The roots filter out 90% of the salt they come into contact with within the saline and brackish water.
  • Low oxygen: Underground tissue of any plant needs oxygen for respiration. The mangrove root system absorbs oxygen from the atmosphere.
  • Store Freshwater: Mangroves, like desert plants, store fresh water in thick succulent leaves.
  • Mangroves are viviparous: Their seeds germinate while still attached to the parent tree. Once germinated, the seedling grows into a propagule. 
• The Sundarbans in West Bengal are the largest mangrove region in the world and a UNESCO World Heritage Site.
• The second largest mangrove forest in India is Bhitarkanika (Ramsar site) in Odisha created by the two river deltas of Rivers Brahmani and Baitarani.

Importance of Mangroves

• Natural Coastal Defence: A mature mangrove belt (50 years old and 100–1,000 m wide) can reduce wave energy by 7–55%, significantly lowering the impact of cyclones, storm surges and coastal flooding compared to non-mangrove coastlines.
• Biodiversity Hotspots: India’s mangroves support about 4,011 species, including 920 plant species and 3,091 animal species.
• Climate Change Mitigation (Blue Carbon): Mangroves store 7.5–10 times more carbon per acre than tropical forests.
• Livelihood and Economic Security: Mangrove ecosystems support millions of livelihoods globally through fisheries, aquaculture, eco-tourism and restoration activities, providing income security for vulnerable coastal communities.
• Cost-effective Nature-based Solutions: By combining disaster risk reduction, biodiversity conservation and carbon sequestration, mangroves offer a low-cost, high-impact solution compared to engineered coastal defences.

Source:PIB