Surviving the Coastal Environment
Like in any other plants, underground mangrove tissues need oxygen. In non-waterlogged soils, the air located in the pores of the soil is sufficient to meet the oxygen needs of the roots. In waterlogged soils, pores are filled with water, and too little oxygen is present to meet the plants’ needs. Mangrove roots tissue is very porous, and it is through thees pores (called lenticels) that oxygen is transmitted from the aerial roots to the underground parts of the plant. In addition to providing oxygen to the buried roots, mangrove’s rooting system play an important role in the plant’s anchorage and stabilization in the very fine and soft sediments.
Young red mangrove tree (Rhizophora mangle)
Prop roots shooting out of a red mangrove tree’s branches (Rhizophora mangle)
Partially submerged prop roots during high tide (Rhizophora mangle)
Pneumatophores (aerial roots) of black mangrove trees (Avicennia germinans) at low tide
Just like any other plants, mangroves rely on their roots to uptake water; however, because of the high salt concentration in ocean water, mangroves have developed several ways to deal with salt. The principal mechanisms to deal with salt include exclusion by roots, tolerance of tissues to high salt concentration, and excretion through glands at the basis of leaves. It is not uncommon to see deposits of salt crystals on leaves, as here on black mangrove leaves.
Salt crystals on the leaves of a black mangrove tree (Avicennia germinans)