Incorporation of C-Kaurene into the Gibberellin of a Higher Plant (Pharbitis nil Chois)

Enzymic formation of ¹⁴C-kaurene from 2-¹⁴C-mevalonate was carried out with a cell-free system of Cucurbita pepo L. It was shown that either heating of the enzyme system or the addition of the growth retardants (2-chloroethyl)-trimethylammonium chloride and 2′-isopropyl-4′ (trimethylammonium chloride)-5′-methylphenyl piperidine-1-carboxylate prevented the synthesis of ¹⁴C-kaurene. Experiments in which ¹⁴C-kaurene was applied to seedlings of Pharbitis nil revealed that the kaurene is converted to at least two compounds present in the acidic ethyl acetate fraction, containing free gibberellins, as well as in the second acidic ethyl acetate fraction, containing the released bound gibberellins. One of the compounds cochromatographed with gibberellic acid; the other compound is possibly a break-down product of gibberellic acid with no biological activity.