Salinity is one of the major factors limiting crop productivity, with most crops being relatively salt-sensitive and significantly affected when exposed to NaCl in the range of 50–200 mM. The identification of mechanisms involved in salinity tolerance has primarily focused on model plants and crops. However, plants naturally adapted to highly saline environments offer valuable insights into tolerance to extreme salinity.
Seagrasses are unique angiosperms that evolved from land plants to live entirely submerged in the sea, one of the most dramatic habitat changes achieved by flowering plants. Originating in the Cretaceous (about 140 million years ago), seagrasses colonized the sea forming one of the most productive and widespread coastal ecosystems. This polyphyletic group of basal monocots, consisting of about 72 species, belongs to four families within the Alismatales. Three of these families (Zosteraceae, Cymodoceae and Posidoniaceae) are composed exclusively of marine species, while the fourth (Hydrocharitaceae) includes both seagrasses and freshwater plants. Compared to terrestrial grasses, seagrasses inhabit stable marine environments, absorbing nutrients through both roots and leaves, adapting to high salt concentrations (500 mM Na+), alkaline pH (7.9-8.3), and low essential nutrient availability (<5 µM NO3- or Pi).
Electrophysiological and molecular techniques, along with recent genome availability, allow us to study the mechanisms that enable seagrasses to thrive in saline environments, potentially valuable for developing salt-tolerant crops.