Changes in stoma density and stomatal conductance of 10 tobacco (Nicotiana tabacum) genotypes and its relationships to weather-fleck caused by ozone were studied in controlled field experiments in 2001 and 2002. Under controlled growing conditions in 2002, changes in the activities of 3 antioxidant enzymes in leaves of 5 genotypes were analyzed in relation to the degree of ozone injury following a combined treatment of ozone and low temperatures (10 ℃). The results showed that there were significant differe...