ABSTRACT
Cold, high salinity and water deficit are serious abiotic stresses that restrict plant productivity throughout the world. Generally, these three type of stresses cause an osmotic stress, inducing similar damages in plants. In this chapter we review how the primary metabolism of plants, especially in rice (Oryza sativa), soybean (Glycine max) and maize (Zea mays), is affected by stress, and their responses. The abiotic stresses interfere with the growth, cellular elongation, membrane permeability and integrity, photosynthesis, respiration and ionic homeostasis of plants, moreover causing an imbalance between water relations and yield. Plants respond and adapt to these stresses in order to survive. The mechanisms include stomata closure, growth and ionic homeostasis regulation, accumulation of osmoregulators and compatible osmolytes, photoprotection, induction of antioxidant enzymes and, finally, a major accumulation of unsaturated fatty acids and sugars, in particular those that act like photoprotective molecules which lower reactive oxygen species levels.
