BIOCHEMICAL AND MOLECULAR-BASIS FOR IMPAIRMENT OF PHOTOSYNTHETIC POTENTIAL

Ozone induces reductions in net photosynthesis in a large number of pl ant species. A primary mechanism by which photosynthesis is reduced is through impact on carbon dioxide fixation. Ozone induces loss in Rubi sco activity associated with loss in concentration of the protein. Evi dence is presented that ozone may induce oxidative modification of Rub isco leading to subsequent proteolysis. In addition, plants exposed to ozone sustain reduction in rbcS, the mRNA for the small subunit of Ru bisco. This loss in rbcS mRNA may lead to a reduced potential for synt hesis of the protein. The regulation of O-3-induced loss of Rubisco, a nd implications of the decline in this protein in relation to accelera ted senescence are discussed.