Elevated CO2 influences the plant growth by increasing the
intercellular CO2 concentration, leading to an increase in net
photosynthesis rate (Booker and Fiscus, 2005). Elevated CO2 also
has the benefit of reducing stomatal conductance, thereby,
increasing water use efficiency in crops (Ainsworth and Long,
2005). O3 enters leaves through the stomata and produces reactive
oxygen species (ROS) which diminish photosynthesis, changestomatal conductance by altering calcium influxes, increase
photorespiration, and induce premature leaf senescence (Fiscus
et al., 2005). The decrease in photosynthesis and chlorophyll
content coincides with the alteration in assimilate production
(Sarkar and Agrawal, 2010).