Alteration of Diphenamid Metabolism in Tomato by Ozone

Abstract

Fumigation of tomato (Lycopersicon esculentumMill. ‘Sheyenne’) with low levels of O3had little effect on root absorption, translocation, or conversion of diphenamid (N,N-dimethyl-2,2-diphenylacetamide) to water-soluble conjugates. However, the proportion of specific conjugates was markedly altered in O3-fumigated plants. Twenty-four hours after treatment, the predominant conjugates formed in nonfumigated and fumigated tomato were the β-glucoside (MDAG), and the β-gentiobioside (MDAGB), respectively, ofN-hydroxymethyl-N-methyl-2,2-diphenylacetamide. The ratio MDAG:MDAGB was 8.2:1.0 in nonfumigated tissue and 0.6:1.0 in O3-fumigated tissue. This marked shift toward production of the more polar MDAGB was accompanied by a trend toward increased production of methanol-insoluble residues. A compound having limited stability was extracted from tomato; its probable structure wasN-hydroxymethyl-N-methyl-2,2-diphenylacetamide (MODA). It is a postulated intermediate in the formation of MDAG and MDAGB from diphenamid.