In this thesis, we have compared between the behaviour of three maize cultivars (SR15, Arizona 8601 and Delitop) which differ in their tolerance to salt stress. We proved that maize have different strategies for growth under salinity, which is either avoidance or survival. The Microelectrode Ion Flux Estimation (MIFE) technique is a unique tool which helped in identifying the different cation fluxes associated with salt stress, at tissue cellular and for the first time at vacuolar level and therefore make it possible to determine the salt tolerance level between cultivars. A correlation was found to link the dynamics of K+ (measured from root surface) and H+ (measured from protoplasts) transport in the tested cultivars, which suggest the role of the H+-ATPase in maintaining the plasma membrane charge stability. We modified the MIFE system to make it possible to study transport mechanisms on the vacuole level, Arizona 8601 exhibited a unique salt tolerant property which is vacuolar Na+/H+ anitport activity, this allows the plant to survive the high salt concentration. Arbuscular Mycorrhiza was able to improve the performance of maize under salt stress, and to increase the efflux of proton form the maize root surface. As a general conclusion, the determinants of salt tolerance in maize are genotypic dependent, which is summarized in the ability of the cultivar to tolerate either the ionic/osmotic phase of salt stress. In addition, the MIFE system can be a fast and reliable screening tool for salt tolerance in plants.
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