ABSTRACT
This chapter focuses on the effects of salt stress on the light reactions of photosynthesis and some defense mechanisms, such as osmoprotectants and the antioxidant defense system. Salt stress strongly affects photosynthesis, which is the most fundamental and intricate physiological process in all green plants. A high salt concentration inhibits the growth of plants, reducing the fresh the dry weight of roots, stems, and leaves. Chlorophyll a, chlorophyll b and carotenoids are the main photosynthetic pigments, and they play an important role in photosynthesis, as the changes in their content affect the photosynthetic activity. The lipids in biological membranes, including the thylakoid membranes, are very important not only for the formation of the lipid bilayer but also for the structure and the function of membrane complexes. Osmoprotectants are small, electrically neutral, non-toxic molecules at molar concentrations; they are highly soluble organic compounds that efficiently maintain osmotic balance and stabilize proteins and membranes under salt, drought, or other stresses.
