Physiological effects of salt stress on plant growth

Abstract

Salinity affects plant growth by causing physiological and morphological changes, which reduces its vegetative system. This appears through decreases in stem length, number of leaves, as well as lateral branches and diameter of plant organs.There are two types of salinity: soil salinity and water salinity. Soil salinity means soil characterized by a high percentage of dissolved salts, mostly of which are chlorides, sulfates and carbonates, to a degree harmful to plant growth. If the soil contains dissolved salts in high quantities, water potential can be reduced to negative level. A distinction between salt stress and ionic stress must be noticed. The first term is used when salt concentration is so high that water potential of growing substrate drops to a significant level (05.0 - 1.0 MPa). If the decrease in water potential was slight and undetectable, the effect here is in the form of ionic stress. A simplified definition of salt stress can be given as an increase in the concentration of salt in plant cells to the degree that affects the physiological properties. This is due to a decrease in the water potential of growing substrate which negatively affects the morphological characteristics of plant. Water potential determines the water movement from the soil to the root or from one cell to another.