A halophyte is a salt-tolerant plant that grows in soil or waters of high salinity, coming into contact with saline water through its roots or by salt spray, such as in saline semi-deserts, mangrove swamps, marshes and sloughs and seashores. The word derives from Ancient Greek ἅλας (halas) 'salt' and φυτόν (phyton) 'plant'. Halophytes have different anatomy, physiology and biochemistry than glycophytes. An example of a halophyte is the salt marsh grass Spartina alterniflora (smooth cordgrass). Relatively few plant species are halophytes—perhaps only 2% of all plant species. Information about many of the earth's halophytes can be found in the ehaloph database. The large majority of plant species are glycophytes, which are not salt-tolerant and are damaged fairly easily by high salinity. Classification Halophytes can be classified in many ways. According to Stocker (1933), it is mainly of 3 kinds by habitat, viz. Aqua-halines (aquatic plants) Emerged Halophytes (most of the stem remains above the water level) Hydro-halophytes (whole or almost whole plant remains under water) Terrestro-halines (terrestrial plants) Hygro-halophytes (grow on swamp lands) Mesohalophytes (grow on non-swamp, non-dry lands) Xero-halophytes (grow on dry or mostly dry lands) Aero-halines (epiphytes and aerophytes) Again, according to Iversen (1936), these plants are classified with respect to the salinity of the soil on which they grow. Oligo-halophytes (amount of NaCl in the soil is 0.01 to 0.1%) Meso-halophytes (amount of NaCl in the soil is 0.1 to 1%) Euhalophytes (amount of NaCl in the soil is >1%) For comparison, seawater has a salinity of about 3.5%. See water salinity for other reference levels. Habitats of halophytes Major habitats where halophytes flourish include mangrove swamps, sand and cliff shorelines in the tropics, salt deserts and semi-deserts, the Sargasso Sea, mudflats and salt marshes, kelp forests and beds, salt lakes and salt steppes of the Pannonian region, wash fringes, isolated inland saline grasslands, and in places where people have brought about salination. Salt tolerance One quantitative measure of salt tolerance (halotolerance) is the total dissolved solids in irrigation water that a plant can tolerate. Seawater typically contains 40 grams per litre (g/L) of dissolved salts (mostly sodium chloride). Beans and rice can tolerate about 1–3 g/L, and are considered glycophytes (as are most crop plants). At the other extreme, Salicornia bigelovii (dwarf glasswort) grows well at 70 g/L of dissolved solids, and is a promising halophyte for use as a crop. Plants such as barley