Flurprimidol: Plant Response, Translocation, and Metabolism

Abstract

Flurprimidol was injected into several species to evaluate effects on growth. Height growth was inhibited 85% in bean ( Phaseolus vulgaris L. ‘Black Valentine’) and 90% in California privet ( Ligustrium ovalifolium Hassk.) by the lowest flurprimidol doses (125 and 625 μg/plant, respectively). Shoot growth was further suppressed as doses increased. Gibberellic acid reversed the inhibitory effect of flurprimidol on privet. In June, height growth of field-grown yellow-poplar ( Liriodendron tulipifera L.) and American sycamore ( Platanus occidentalis L.) was uniformly reduced 35% by all flurprimidol doses. By late July, height growth increment decreased linearly as flurprimidol increased from 5 to 40 mg/tree. Thirty-five days after injection of 2.5 mg 14 C-labeled flurprimidol in 1-year-old apple ( Malus domestica Borkh.), 10% had moved into the new shoots, 1.5% into the scion phloem, and 80% remained near the injection site. A high percentage of the 14 C activity was unmetabolized flurprimidol; 95% of the 14 C activity in the xylem, 86% in the phloem, and 75% in the shoot. Although it is not highly mobile, flurprimidol effectively inhibits shoot growth, apparently inhibiting gibberellin synthesis. Chemical names used: α-(1-methylethyl)-α-[4-(trifluoro-methoxy)phenyl]-5-pyrimidinemethanol (flurprimidol).