**4. Increase in CO2 concentration and sugarcane production**

Increases in CO2 concentration directly affect the photosynthesis and stomatal physiology, increase growth rate in many plants [33]. High concentration with increase temperature will alter the plant ability to grow and modify the distribution of weeds across globe and their competitiveness in different habitat [36, 37]. In C4 plats, internal mesophyll cell arrangement is different as compare to C3 plant; help in efficient transfer of CO2 and increase photosynthesis and reduce the photorespiration [33]. In future under increasing CO2 condition, C4 crop may become more vulnerable to increased competition from C3 weeds. Double concentration of CO2 may decrease 30–40% in stomatal aperture and 25–40% transpiration loss in both C3 and C4 plant. Double concentration of CO2 may decrease 30–40% in stomatal aperture and 25–40% transpiration loss in both C3 and C4 plant. In long term field study, LAI (Leaf Area Index) did not increase in any species under elevated CO2 conditions [33]. Bowes [38] discus that under increasing cons. of CO2, starch cons. Also increases in tissue reduce protein content. Elevated CO2 cons. increase the growth and root-shoot ratio [39] and alter the photosynthesis activity in plants. Plants available nitrogen also reduces under elevated CO2 [40]. Leaves carbon-nitrogen ratio increased under increasing CO2.
