Abstract:
Nitrogen (N) is an essential element of the building blocks of almost all plant structures and a vital component of chlorophyll, enzymes, and proteins. It is used in relatively large amounts than other plant nutrients. Therefore, N has been recognized as the most limiting nutrient in crop production systems. Several transformation processes are involved in the nitrogen cycle. Among them, biological nitrogen fixation is an environmentally friendly natural resource for sustainable agricultural systems. Recently, the reports directed to a decrease in agricultural dependence on symbiotic nitrogen fixation due to abiotic stresses. Therefore, abiotic stresses are a topic that increasingly occupies the attention of the world is still a matter of debate. Although physiological mechanisms are affected in more intense abiotic stresses, most research efforts have focused on the study of these processes. In legume plants being grown under symbiotic conditions, one of the primary effects of abiotic stresses is a decline in the rates of symbiotic nitrogen fixation (SNF). In the present chapter, we summarize our current understanding of the factors that are affected by SNF in legumes. Finally, an overview of the available resources and applications of the physiologicalsystemforunderstandingthecomplexresponsesoflegumestoabiotic stresses is provided. The overall conclusion was that all physiological mechanisms are important in understanding the regulation of N2 fixation and its response to abiotic stresses.