DOES CO2 MODIFY THE EFFECT OF SO2 ON VARIEGATED LEAVES OF CHLOROPHYTUM-COMOSUM (THUNB) BAK

Stomatal aperture and conductance were greater in the green parts of C hlorophytum comosum (Thunb) Bak var. variegatum leaves than in the whi te parts. A strong decrease in net photosynthesis (P-N) was measured i n green parts of the leaves after fumigation with 80 mu l l(-1) SO2 fo r 45 min. However, the inhibitory effect of SO2 on P-N was less expres sed at 1000 mu l l(-1) CO2 than at 0 and 380 mu l l(-1) CO2. The decre ase in P-N after exposure to SO2 was accompanied by closure of the sto mata, both in the green and white parts of the leaves, at all tested C O2 concentrations (0, 380 and 1000 mu l l(-1)). Superoxide dismutase ( SOD) activity strongly increased at 1000 mu l l(-1) CO2 both in the gr een and white parts of the leaves as compared with 0 and 380 mu l l(-1 ) CO2, indicating better adaptation to oxidative stress. Exposure to 8 0 mu l l(-1) SO2 increased SOD activity at 0 and 380 mu l l(-1) CO2, b ut not at 1000 mu l l(-1) CO2.