Influence of ozone on transgenic tobacco plants expressing reduced quantities of Rubisco

Abstract

ABSTRACT Rbc S‐antisense transformed tobacco plants ( Nicotiana tabacum cv. Petit Havana) expressing reduced quantities of Rubisco protein were used to examine the role of Rubisco quantity in determining ozone (O 3 ) sensitivity. Transformed and wild‐type plants were exposed to O 3 in the greenhouse and in the field. Stomatal conductance, net photosynthesis and Rubisco protein quantity were measured at various times. Antisense‐transformed genotypes responded to O 3 by exhibiting rapid, severe foliar necrosis. The wild‐type plants responded more slowly, exhibiting limited injury. Decreases in stomatal conductance, net photosynthesis or Rubisco quantity in plants exposed to O 3 were not observed in asymptomatic leaves. Total biomass was lower for the transformed genotypes and decreased in both genotypes after exposure to O 3 . Shoot–root ratio and specific leaf area were higher in the transformed genotypes and increased in both genotypes with exposure to O 3 . Measurements of intercellular airspace demonstrated the presence of larger intercellular spaces in the transformed plants. The indirect effects of the rbc S antisense transformation, including morphological changes in the leaf, probably rendered the transformed plants more sensitive to the oxidant. The decreased quantity of Rubisco is not thought to be directly related to increased O 3 sensitivity in the transformed plants.