Understanding the consequence of environmental stress for accumulation of secondary metabolites in medicinal and aromatic plants

Abiotic stresses are the most critical hurdle for the growth and development of the plants. The abiotic stresses are salinity, heat, drought, flood, heavy metals and plant nutrients. Plants develop different tolerance mechanisms such as adjustment of membrane system, maintenance of cell wall architecture, production of secondary metabolites and antioxidants, phytohormones, and accumulation of osmolytes in response to abiotic stresses. The secondary metabolites, developed through various physiological and biochemical process, play vital role to cope up with different stresses. The presence of these compounds in the plant acts as an interface with its adverse environment. Primary metabolites are the precursors for the secondary metabolites production in plants, but its concentration and transport are influenced with the changes in climatic conditions. Stress conditions also enhance the expression level of corresponding genes involved in the natural product biosynthesis. The secondary metabolites produced as a result of abiotic stresses are involved in plant defence system for survival. Secondary metabolites never participate in building block processes rather they function to deal with many external agents. They also protect plant from various biotic stresses and facilitate in pollination and fruit dispersal mechanism by attracting the pollinating and dispersing agent through their beautiful colour and fragrance. In this review, we tried to figure out how abiotic stresses affect the production of secondary metabolites in medicinal and aromatic plants.