Delineating the mechanisms of elevated CO2 mediated growth, stress tolerance and phytohormonal regulation in plants.

Global climate change has drastically affected natural ecosystems and crop productivity. Among several factors of global climate change, CO2 is considered to be the dynamic parameter that will regulate the responses of all biological system on earth in the coming decade. A number of experimental studies in the past have demonstrated the positive effects of elevated CO2 on photosynthesis, growth and biomass, biochemical and physiological processes such as increased C:N ratio, secondary metabolite production, as well as phytohormone concentrations. On the other hand, elevated CO2 imparts an adverse effect on the nutritional quality of crop plants and seed quality. Investigations have also revealed effects of elevated CO2 both at cellular and molecular level altering expression of various genes involved in various metabolic processes and stress signaling pathways. Elevated CO2 is known to have mitigating effect on plants in presence of abiotic stresses such as drought, salinity, temperature etc., while contrasting effects in the presence of different biotic agents i.e. phytopathogens, insects and herbivores. However, a well-defined crosstalk is incited by elevated CO2 both under abiotic and biotic stresses in terms of phytohormones concentration and secondary metabolites production. With this background, the present review attempts to shed light on the major effects of elevated CO2 on plant growth, physiological and molecular responses and will highlight the interactive effects of elevated CO2 with other abiotic and biotic factors. The article will also provide deep insights into the phytohormones modulation under elevated CO2.