Metabolism of 3-indoleacetic acid in tobacco exposed to the air pollutant peroxyacetyl nitrate

The influence of an air pollutant, peroxyacetyl nitrate (PAN),on 3-indoleacetic acid (IAA) and its metabolites in tobaccoplants was studied. Plants were administered IAA-2-¹⁴C immediatelybefore or after gassing with PAN. After 8 hr metabolism in thedark or in the light the plants were separated into shoot tipand damaged and undamaged leaf areas prior to analysis. PAN-treatedplants which metabolized in the light and produced partiallydamaged leaves showed a relative increase in unmetabolized IAAin the leaves compared to control treatments. Several suspectedindole conjugates from leaves of PAN-treated plants containedrelatively less label than controls. Plants which metabolizedin the dark and showed no visible external damage also demonstratedchanges in indoleacetic acid metabolism. The changes were qualitativelydifferent however from those observed in damaged tissue. UndamagedPAN-treated tissue consistently had less of certain unidentifiedcompounds. It was concluded that PAN is capable of causing biochemicallesions in indole metabolism prior to the expression of visibledamage. ¹ Present address: Canada department of Agriculture, ResearchBranch, 2560 Chemin Gomin, Ste-Foy, Quebec 10, Canada. (Received June 29, 1971; )