| Salt stress is one of the major abiotic stresses to the plants in the world. High concentration of sodium in soils is deleterious to growth and development of higher plants. The detrimental effects of salt on plants are a consequence of both water deficit that results from the relatively high solute concentrations in the soil and excessive Na~+ concentrations in the cytoplasm. Excessive Na~+ not only alters ion ratios and affects critical biochemical processes in the cytoplasm, but also increases plasma membrane injury and causes malondialdehyde (MDA) accumulation. The strategies for plants eliminating the Na~+ toxicity include: suppressing Na~+ influx, increasing Na~+ efflux and compartmentalizing Na~+ in vacuoles. Up to date, it is known that Na~+ can be transported into plant cells by K~+ transporters, but the details in molecular mechanisms about Na~+ influx are not clear enough. Na~+/H~+ antiporters located in plasma membrane and vacuolar membrane mediate Na~+ efflux or compartmentalization, which are driven by the proton gradient established by the plasma membrane H~+-ATPase or tonoplast H~+-ATPase and V-type H~+-PPase. Na~+ compartmentalization can not only avert the toxic effects of Na~+ in the cytoplasm but also maintain cell turgor and enhance the capacity of water uptake.As the development in plant molecular biology about salt and drought tolerance, great progresses have been achieved in signal transduction, regulations of transcript, ion homeostasis, ROS scavenging systems and compatible solutes synthesis mechanisms in plant especially for Arabidopsis. However, Arabidopsis is a typical glycophyte; it can't reveal all salt tolerance mechanisms, especially for some specialized mechanisms in halophytes. Salt cress (Thellungiella halophila;...
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