Une plante ligneuse est une plante qui fabrique de la lignine, ou plutôt des lignines, macromolécules organiques donnant à la plante sa solidité. Les lignines étant le deuxième constituant du bois, après la cellulose, le bois, aussi appelé xylème, caractérise donc les plantes ligneuses dont il est le principal tissu de structure (le mot latin lignum et le mot grec xylon signifient bois). Toutefois, la notion de plante ligneuse est une catégorisation végétale intuitive qui n'est pas précisément classificatoire (taxonomique) en botanique.
Mangroves are various types of trees up to medium height and shrubs that grow in saline coastal sediment habitats in the tropics and subtropics – mainly between latitudes 25° N and 25° S. The remaining mangrove forest areas of the world in 2000 was 53,190 square miles (137,760 km²) spanning 118 countries and territories. The word is used in at least three senses: (1) most broadly to refer to the habitat and entire plant assemblage or mangal, for which the terms mangrove forest biome, mangrove swamp and mangrove forest are also used, (2) to refer to all trees and large shrubs in the mangrove swamp, and (3) narrowly to refer to the mangrove family of plants, the Rhizophoraceae, or even more specifically just to mangrove trees of the genus Rhizophora. The term "mangrove" comes to English from Spanish (perhaps by way of Portuguese), and is likely to originate from Guarani. It was earlier "mangrow" (from Portuguese mangue or Spanish mangle), but this was corrupted via folk etymology influence of "grove".
The mangrove biome, or mangal, is a distinct saline woodland or shrubland habitat characterized by depositional coastal environments, where fine sediments (often with high organic content) collect in areas protected from high-energy wave action. Mangroves dominate three-quarters of tropical coastlines. The saline conditions tolerated by various mangrove species range from brackish water, through pure seawater (30 to 40 ppt(parts per thousand)), to water concentrated by evaporation to over twice the salinity of ocean seawater (up to 90 ppt).