Definition and Classification of Halophytes

Abstract

At this moment, there is a plethora of definitions that are attributed to halophytes; due to their taxonomical and ecological complexity, there is no consensus on a unique definition of a halophyte. This issue has been a matter of debate in several papers focused on halophytes' biology and inherent difficulties. As shown, this heterogeneity is suggested, first of all, by the large number of interpretations made by various authors over time. Thus, Chapman (1960) describes halophytes as "salt-tolerant plants," Fernald (1950) regards them as plants "growing in saline soils," and Dansereau (1957) defines them as "plants that grow exclusively on salt soil, e.g., Salicornia species." Other definitions include plants of salty or alkaline soils (Correll and Johnston 1970); plants that can tolerate salt concentrations found in salty soils (Oosting 1956); and plants tolerant of various mineral salts in the soil solution, usually sodium chloride (Lawrence 1951). Waisel (1972) defines halophytes as plants that grow and complete their entire life cycle in habitats where the salt content is high. Usually, this term is restricted only to plants that appear constantly on salt areas. Waisel also uses another term-pseudohalophytes ("false" halophyte) to refer to plants that occupy only local nonsaline ecological niches in an overall saline environment, or those that occur in such environments only for short periods, i.e., during the rainy season. Duncan (1974), making a list of halophytes which vegetate on the Atlantic and Gulf coasts of North America and Mexico, regards them as species that can tolerate seawater, "pure or diluted." Grigore et al. (2010) chronologically reviewed more than 40 definitions of halophytes, stating that the huge variability in approaching such an ecological group derives from historical period, from authors' background, and from reinter-pretations of previously stated definitions. Closely related to the richness of halophyte definitions, the multitude of saline habitats, whose terminology is still problematic, can explain the lack of a consensus