The global population growth has created the need of increasing food production. Saline stress inhibits agricultural crop yield and forest production. In many cases, this situation leads to the abandonment of degraded areas and to desertification. Selecting species resistant to this conditions, knowing the physiological mechanisms involved and genetic improvement, represent great challenges so as to increase food and wood production. In a basic theoretical framework and through illustrative outlines which summarize complex metabolic processes; this book presents the adaptive mechanisms of two species tolerant to salinity which have been studied for fifteen years. The obtained results, gathered in this book, show that the internationalization of investigation projects carried out in Argentina are possible. Plant Physiology contributes to filling the gap within the Spanish literature regarding plant tolerance mechanisms to saline stress.