Auxinlike Activity and Metabolism of Mefluidide in Corn (Zea mays) and Soybean (Glycine max) Tissue

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Abstract
Mefluidide {N-[2,4-dimethyl-5-[[(trifluoromethyl) sulfonyl] amino] phenyl] acetamide} was evaluated for effects on corn [Zea mays (L.) ‘Pioneer 3535’] coleoptile elongation. Mefluidide at 10-8 M, 10-7 M, and 10-6 M stimulated elongation approximately equal to growth stimulations with 10-6 M indoleacetic acid (IAA). Polar transport of 14C-IAA from donor agar blocks through corn coleoptiles and into receiver agar blocks after 12 h was increased 246% by 10-4 M mefluidide and inhibited 82% by 10-3 M mefluidide. Mefluidide-related chemicals (10-4 M) lacking a trifluoromethyl-sulfonyl-amino chain at the 1-position of the phenyl ring did not alter 14C-IAA transport. IAA transport was increased 97% when the acetamide chain at the 5-position was absent and 255% when the methyl in the 4-position was absent, and it decreased 65% when the methyl at the 2-position was absent. Polar transport of 14C-IAA through soybean [Glycine max (L.) Merr. ‘Williams’] hypocotyls was not altered by 10-4 M mefluidide; however, 10-3 M mefluidide increased IAA transport 116%. After 6 h, corn coleoptiles metabolized 14% of the mefluidide absorbed and soybean metabolized 54% of the mefluidide absorbed from 14C-mefluidide solutions (10-6 M). Differences in the rate of metabolism of mefluidide in meristematic tissue of corn and soybean may explain differences in mefluidide effects on auxin transport in corn and soybean.