THE ADAPTIVE FEATURES OF HALOPHYTES:-
1) High osmotic concentration of the cell sap: - The halophytes have cell sap concentration at much higher level than that of the surrounding sea water, so that they can absorb water from the sea. This is the single most important adaptive feature with out which they would not live.
In fact, this feature is present in all the marine plants such as sea weeds and the kelps. It is as much as 12 times higher than the one found in ordinary land plants.
2) Presence of thick epidermis: - The leaf epidermis is thickly cuticularised to prevent excessive transpiration. The stomata are less frequent or sunken on the upper epidermis and located mostly along the lower epidermis, which is not much exposed to direct harsh sunlight in this, they are similar to desert plants or xerophytes.
3) Presence of salt excreting glands: - On the leaf surface, they have special glands through which they get rid of the excess sea salt that accumulates in the body.
4) Vivipary germination: - this is yet another feature unique to these plants, in which the seed begins to germinate while the fruit is still attached to the parental tree. The radicle that comes out is massive and tapering. When it the seed finally gets detached from the parent it sinks vertically down like a dart due to this massive radicle and the radicle gets embedded in the mud/sand. There the further development of a new tree continues.
Thus, the possibility of the seed being washed away with the tides in to deep sea and lost is entirely eliminated.
It is because of this habit, the halophytes (Mangroves) develop thick impenetrable forests wherever they grow.
The nature is clever than the man thinks.
Ecology of Halophytes.