From the SOD activity it is seen that the Fe-SOD activity showed the most sensitivity to induced oxidative stress denoting higher ROS. This emphasizes the phototoxic effects of ROS. The increased sensitivity in the fass-5 B regulatory subunit mutant shows that the regulation of PP2A plays a role in the mediation of SOD activity in response to oxidative stress. The DNA damage as a result of oxidative stress is higher in the homozygous recessive fass-5 mutant but for the heterozygous fass-5 genotype we did not detect marked changes in histone H2A phosphorylation . There seems to be a little positive effect.