Chlorine

Chloride ion is abundant in nature. Plants need it as a micronutrient. Its deficiency in plants is observed in rainy inland regions. Chloride salinity is widespread all over the world in irrigated areas. Plant species and cultivars vary in their sensitivity to excess Cl^- in the soil solution. The transport of Cl from the soil to the plant and its transport inside plant cells involve chloride channels and energy investment. It accumulates in leaves and to a lesser extent in fruits and seeds. There is a competition in the uptake and accumulation between nitrate and chloride, the two anions that are taken in large quantities by plants. Continuous presence of nitrate in the soil solution near the roots reduces chloride uptake by a factor of 2–6, enabling sensitive plants to overcome Cl salinity. The main reasons for excessive Cl in soils are excess evaporation from irrigated lands, sea inundations, and use of saline water for irrigation.