ABSTRACT
This chapter presents the information available on the mechanistic details of salt tolerance in aquatic macrophytes, especially in submerged aquatic macrophytes. Aquatic macrophytes are defined as aquatic plants that can be observed by the naked eye and may be floating, submerged, or emergent. The concept of stress, as described by H. Selye, is the "state of the whole organism or its partial mobilization affected by a strong external action." Salinity may affect a plant at various stages of its life, at both morphological and cellular levels, reducing plant growth and yield germination of seeds, and growth of roots and shoots. The aquatic macrophytes are distributed all over the world, except in some very deep and cold-water lakes in polar environments. The distribution of aquatic macrophytes depends on two major factors: water quality and quantity. Photosynthesis, the biochemical process of carbon dioxide assimilation, is known to be sensitive to many environmental stresses.
