ABSTRACT
Unfavorable environmental conditions suspend the development and growth of plants and also limit their production that ultimately threatens the food security of the world. Various abiotic factors such as drought, salinity, temperature, heavy metals, and excessive light hamper the photosynthetic and respiratory process in plants. These factors either directly inhibit the activity of enzyme involved in the above-mentioned process or indirectly distort the structure of thylakoids, chloroplast and degrade photosynthetic pigments via the formation of reactive oxygen species that again inhibits the above-mentioned processes and directly lowers the yield of the plants. However, to survive in these hostile environment, plants have developed an extensive network of protective metabolites comprising of osmolytes and secondary metabolites. Additionally, various reports have also demonstrated that exogenous application of certain chemicals such as salicylic acid, nitric 352acid, calcium, melatonin etc. can boost the generation of the metabolites that ultimately lower the formation of cytotoxic by-products in plants. Here, we provide a detailed overview of the research conducted on photosynthetic and respiratory machineries that highlights the negative effects of abiotic stresses on these processes along with the efficacy of protective compounds that restores proper functioning of these pathways. Based on our studies, we tried to present detailed information of the plant responses to unfavorable environmental conditions, and more efficient protective network of metabolites that can improve photosynthetic and respiratory machinery so as to develop stress-resilient crop plants.
