Light (High Light/UV Radiation) Modulates Adaptation Mechanisms and Secondary Metabolite Production in Medicinal Plants

Traditional medicines have long been making the use of plants that produce the secondary metabolites of therapeutic importance. However, in order to meet the ever-growing and exponential demand of herbal medicine, alternative methods need to be explored to enhance the yield and quality of the pharmaceutically important secondary metabolites. Amid such a situation, Ultraviolet (UV) rays as elicitors have caught a lot of attention for increasing the production of therapeutically important secondary metabolites due to their promising nature. Medicinal plants develop a variety of secondary metabolites as one of their defense mechanisms. They mainly provide photoprotection by filtering UV rays and quenching reactive oxygen and nitrogen species through the elevation of enzymatic and non-enzymatic antioxidant agents created on exposure to UV irradiation. Each of the UV rays i.e., UV-A, UV-B and UV-C, has a distinct impact on the plant metabolism and holds the potential to make changes at a molecular level by up-regulating and down-regulating genes. This chapter aims to shed light on the outcome of exposing plants to different types of UV irradiation and on different adaptive mechanisms plants go in for producing the commercially and therapeutically important secondary metabolites.