Saline habitats occur along bodies of saltwater, e.g., coastal salt marsh, and inland within high-evaporation basins, saline lakes, and lowlands of dryland and desert topography. The electrolytes sodium (a cation) and chloride (an anion) are extremely toxic to most plants at relatively low soil water concentrations, due to deleterious effects on cellular metabolism and ultrastructure.
- True halophytes are plants that thrive when given water having greater than 0.5% NaCl. A small number of plant lineages have evolved structural, phenological, physiological, and biochemical mechanisms for salt resistance, and true halophytes have evolved convergently in numerous, related families.
- Xerohalophytes are the desert species of halophytes. Desert and coastal halophytes possess the same mechanisms for dealing with salt toxicity and salt stress. Species living in both saline habitats commonly belong to the same phylogenetic lineages.
- There are marine phanerogams (seed-bearing plants) that live completely submerged in seawater.
A saline habitat often has a low diversity of plants, sometimes even just one dominant species, because so few species are able to resist salt damage, and those that do have special microhabitats that are optimal.