Avicennia marina marina

Description

Avicennia marina, commonly known as grey mangrove or white mangrove, is a species of mangrove tree classified in the plant family Acanthaceae (formerly in the Verbenaceae or Avicenniaceae). As with other mangroves, it occurs in the intertidal zones of estuarine areas.Grey mangroves grow as a shrub or tree to a height of three to ten metres, or up to 14 metres in tropical regions. The habit is a gnarled arrangement of multiple branches. It has smooth light-grey bark made up of thin, stiff, brittle flakes. This may be whitish, a characteristic described in the common name. The leaves are thick, five to eight centimetres long, a bright, glossy green on the upper surface, and silvery-white, or grey, with very small matted hairs on the surface below. As with other Avicennia species, it has aerial roots (pneumatophores); these grow to a height of about 20 centimetres, and a diameter of one centimetre. These allow the plant to absorb oxygen, which is deficient in its habitat. These roots also anchor the plant during the frequent inundation of seawater in the soft substrate of tidal systems. The flowers range from white to a golden yellow colour, are less than a centimetre across, and occur in clusters of three to five. The fruit contains large cotyledons that surround the new stem of a seedling. This produces a large fleshy seed, often germinating on the tree and falling as a seedling. The grey mangrove can experience stunted growth in water conditions that are too saline, but thrive to their full height in waters where both salt and fresh water are present. The species can tolerate high salinity by excreting salts through its leaves