Mechanisms and cellular strategies of salinity tolerance (NaCl) in plants

The problem of salinity is multiple. In addition to salt stress, ion toxicity (Na+ and Cl- dissolved in irrigation water or in soil solution), and mineral nutrition perturbation, plants have difficulty absorbing water from soil because of its elevated osmotic pressure, which leads to water stress and thus complicates and impairs their physiological state in an exponential way. Consequently, cells try to adjust their water potential by ion homeostasis regulation via vacuolar compartmentation and (or) extrusion out of the cell of the toxic ions (Na+ and Cl-). Nevertheless, if this is not sufficient, the plant has to use another way to face salt stress, which consists in the synthesis and accumulation of a class of osmoprotective compounds known as compatible solutes, mainly amino compounds and sugars. Energetically, this osmotic strategy is more expensive than ion homeostasis regulation. A secondary aspect of salinity stress in plants is the stress-induced production of reactive oxygen species leading to an oxidative stress whose damage reduction could be realized via the production of antioxidants. Perception and signal mechanisms represent the first events of plant stress adaptation, and the main pathways followed are calcium, abscissic acid (ABA), mitogen-activated protein kinases (MAPKinases), salt overly sensitive (SOS) proteins, and ethylene. © 2011 Published by NRC Research Press.