A lack of correlation between the biological activity and rate of metabolism of ent-(3H)-17-kaurenoic acid by seedlings of dwarf rice cv. Tan-ginbozu

Abstract

Significant leaf sheath elongation occurred within 24 hr after application of 10 μg (0.67, μCi) of ent-(³H)-17-kaurenoic acid (KA) to individual seedlings of dwarf rice cv. Tan-ginbozu, but this growth was unaccompanied by production of significant levels of radioactivity in more polar, acidic, ethyl acetate-soluble metabolites of (³H)-KA. However modest levels of radioactivity appeared in the highly water-soluble fraction by hour 24, subsequent to the most rapid phase of KA-induced growth. Growth continued and by hour 48 was accompanied by the appearance of small amounts of radioactivity in polar, acidic products. It would appear that KA per se, and not its metabolic products, may be responsible for the leaf sheath elongation noted at hour 24. On the speculation that it might be a metabolite of KA, gibberellin A₁₄ (GA₁₄) was applied simultaneously with (³H)-KA to individual rice seedlings. Several changes in the metabolism of ³H-KA in the presence of GA₁₄ were noted, and GA₁₄ antagonized the KA-induced sheath elongation.