Evidence of Singlet Oxygen Participation in the Chlorophyll-Sensitized Photooxidation of Indoleacetic Acid

Abstract

Chlorophyll-sensitized photooxidation of indoleacetic acid (IAA)-with chlorophyll extracted from Pisum sativum L. cv. Alaska W.R.-was determined in the presence of deuterium oxide and known quenchers of singlet oxygen ((1)O(2)) to explore the involvement of (1)O(2) in the reaction. O(2) uptake was measured in light in a buffered aqueous micellar system containing Triton X-100, KCl, chlorophyll, and IAA. The rate of O(2) uptake was zero in darkness. The reaction was stimulated by deuterium oxide and inhibited by sodium azide indicating that (1)O(2) participated in IAA photooxidation. Both mannitol and superoxide dismutase failed to inhibit O(2) uptake suggesting that neither the hydroxyl radical nor the superoxide anion played a significant role in the reaction.