Mangrove Plants

Mangroves Plants and Shrubs

Environment

Mangroves are defined as assemblages of salt tolerant trees and shrubs that grow in the intertidal regions of the tropical and subtropical coastlines (marshlands). They grow luxuriantly in the places where freshwater mixes with seawater and where sediment is composed of accumulated deposits of mud or marshlands.

Locations

Some of the best mangroves in the world occur in the alluvial deltas of Ganga, Gadavari, Krishana, Kaveri and in the islands of Andaman and Nicobar. This mangrove vegetation all along Indian coastline in sheltered estuary, tidal creeks, back waters, salt marshes-covering about 6700 sq.km. Which is about 7% of the worlds' total mangrove areas.

Fifteen areas have been selected on the basis of the recommendations of the National Committee on wetlands. They are, Andman and Nicobar, Sundarbans in west Bengal, Bhitarkanika in Orissa, Coringa, Krishana and Godavari delta in A.P point Calimere in T.N, Gulf of Kutch in Gujarat, Coondapur in Karnataka, Vembanad in Kerala. Apart these, an additional 15 mangroves have been identified such as subernarekha, Devi & Dhama in Orissa- Ramanard in T.N. Dakshin Kanada in Karnataka, Kalsuri in Maharashtra etc.

Flora

Plants of mangroves are generally divided into two groups, namely, i) true or exclusive mangroves species and ii) associated mangrove species. True mangrove species grow only in mangrove environment and do not extend into terrestrial plant community and are morphologically, physiologically and reproductively adapted to saline, waterlogged and anaerobic condition.

Adaptation

Mangrove environment is highly dynamic and harsh and mangrove species are variously adapted to cope with these environmental conditions.

Breathing roots: Underground tissue of any plant requires oxygen for respiration and in mangrove environment, oxygen in soil is very limited or nil. This necessitates mangrove root system to take up oxygen from the atmosphere. For this purpose, mangrove species have specialized above ground roots called breathing roots or pneumatophores. In some species, these roots are pencil sized and peg like whereas in some other species they look like a knee. These roots have numerous pores through which oxygen enters into the underground tissues. In some plants buttress roots function as breathing roots and also provide mechanical support to the tree.

Silt roots: In some mangrove species, roots diverge from stems and branches and penetrate the soil some distance away from the main stem as in the case of banyan trees. Because of their appearance and because they provide the main physical support to these they are called as stilt roots. These roots also have many pores through which atmospheric oxygen enters into the roots.

Vivipary: Saline water, unconsolidated saline soil with little or no oxygen is not a conducive environment for seeds to germinate and establish. To overcome this, mangrove species have unique way of reproduction, which is generally known as vivipary. In this method of reproduction, seeds germinate and develop into seedlings while the seeds are still attached to the parent tree. These seedlings are normally called as propagules and they photosynthesize while still attached to the mother tree. The parent tree supplies water and necessary nutrients. They are buoyant and float in the water for sometime before rooting themselves on suitable soil.

Uses

Mangrove wetland is a multiple use ecosystem. It is considered as a best form of coastal bioshield since it plays a critical role in reducing the impact of cyclonic storms, hurricanes and tsunami on human lives and properties (Danielsen et al., 2005; Selvam, 2005). It also avoids or reduces soil erosion. It enhances fishery productivity of the adjacent coastal waters by acting as a nursery ground for commercially important fish, prawn and crabs and supplying organic and inorganic nutrients. They are also rich in biodiversity and act as habitats for wildlife.

Question which was asked in UPSC CMS

99. Which one of the following is an appropriate description of mangrove plants?

(a) Large wood-yielding trees of !he tropical forests
(b) Plants in marshy areas with breathing roots
(c) Succulent plants that can thrive in arid/ desert areas
(d) Vast grassland areas interspersed with deciduous trees and thorny bushes

Answer: B