AVICENNIA MARINA

Recently, the scientists for the first time have decoded the reference-grade whole genome sequence of a highly salt-tolerant and salt-secreting mangrove species, Avicennia marina.
This study was led by the Department of Biotechnology (DBT)-Institute of Life Sciences, Bhubaneswar.

Important points:

It is one of the most prominent mangroves species found in all mangrove formations in India.
It is a salt-secreting and extraordinarily salt-tolerant mangrove species that grows optimally in 75% seawater and tolerates >250% seawater.
It is among the rare plant species, which can excrete 40% of the salt through the salt glands in the leaves, besides its extraordinary capacity to exclude salt entry to the roots.
It is also referred to as grey mangrove or white mangrove.

Significance:

This study assumes significance as agriculture productivity globally is affected due to abiotic stress factors such as limited water availability and salinization of soil and water.
Availability of water is a signiﬁcant challenge to crop production in dryland areas, accounting for 40% of the world’s total land area.
Salinity is prevalent in 900 million hectares globally (with an estimated 6.73 million ha in India), and it is estimated to cause an annual loss of 27 billion USD.
The genomic resources generated in the study will pave the way for researchers to study the potential of the identified genes for developing drought and salinity tolerant varieties of important crop species of the coastal region that is significant for India with 7,500m of coastline and two major island systems.

Mangrove

A mangrove is a small tree or shrub that grows along coastlines, taking root in salty sediments, often underwater.
The word ‘mangrove’ may refer to the habitat as a whole or to the trees and shrubs in the mangrove swamp.
Mangroves are flowering trees, belonging to the families Rhizophoraceae, Acanthaceae, Lythraceae, Combretaceae, and Arecaceae.
They can survive under extreme hostile environments such as high salt and low oxygen conditions.
Underground tissue of any plant needs oxygen for respiration. But in a mangrove environment, the oxygen in soil is limited or nil. Hence the mangrove root system absorbs oxygen from the atmosphere.
Mangroves have special roots for this purpose called breathing roots or pneumatophores.
These roots have numerous pores through which oxygen enters the underground tissues.
Mangroves, like desert plants, store fresh water in thick succulent leaves.
A waxy coating on the leaves seals in water and minimises evaporation.
Their seeds germinate while still attached to the parent tree. Once germinated, the seedling grows into a propagule.
The mature propagule then drops into the water and gets transported to a different spot, eventually taking root in a solid ground.