Peanut is an important crop in the semi-arid regions of the world. Both, irrigation and well water can provide the water necessary for it. It is a nutritious seed nut crop and has manyfold uses. As such, research on this crop is imperative. This book reviews physiological aspects, keeping in mind the changing agroclimatic conditions. Growth, development and yield are described on the basis of cellular and morphological manifestations. Being a C3 plant, the photosynthesis and respiration in peanuts is critically viewed specially under varying environment conditions and genotypes. The study of nitrogen assimilation and biological nitrogen fixation have been presented in light of the prevalent environmental and gene effects. The role of plant growth regulators in peanuts is elaborated on, stating up-to-date mode of actions. Special emphasis has been given to mechanisms of abiotic stress effects. The chapters (13) are arranged on the basis of physiology, cellular structure, biochemistry, molecular and genomics concepts.