Antioxidants and growth regulators counter the effects of O 3 and SO 2 in crop plants

Abstract

Antioxidant compounds such as ethylenediurea (EDU); N-[2-(2-oxo-1-imidazolidinyl) ethyl]- N′-phenylurea have been found to be effective in suppressing O 3-induced leaf injury. Gibberellic acid (GA) inhibitors such as paclobutrazol, tetcyclaics and flurprimidol suppress visible SO 2-induced injury. Antioxidant compounds are relatively ineffective in protecting plants from SO 2-induced injury, while GA inhibitors are ineffective in protecting plants from O 3 injury. EDU and GA inhibitors do not alter the stomatal behavior, however they can induce resistance to air pollutants stress. Furthermore, EDU and paclobutrazol (PP 333) do not alter foliar membrane lipid composition. EDU does not alter polyamine composition. This suggests that the mechanism of plant tolerance to air pollutant exposure is probably biochemical rather than biophysical. Free radical scavenging enzymes or endogenous antioxidant compounds are more important than stomatal restriction of pollutant diffusion to the sensitive leaf mesophyll sites.