ABSTRACT
The Earth’s surface has, and probably had then, a low but variable salinity, in contrast to the marine environment, which has had a constantly high salinity for at least the last billion years. A few plant species arehalophytes that can grow at relatively high salinity, although their optimum growth almost always occurs at salinities that of seawater. Few crop species are tolerant of even mild salinity, and many of the world’s staple food crops are notably salt-sensitive. Crop responses to salinity in irrigated agriculture will be important for human habitation of Earth in the twenty-first century and beyond, because they are vital to confronting what has been called humankind’s “salinity dilemma.” Low calcium (Ca) concentrations are associated with symptoms such as a decrease in membrane integrity, but plant responses to salinity are also mediated by Ca fluxes in the cytoplasm that are disrupted by salinity-induced Ca deficiency.
