Inhibition of gibberellin biosynthesis by paclobutrazol in cell-free homogenates ofCucurbita maxima endosperm andMalus pumila embryos |
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Authors: | Peter Hedden Jan E. Graebe |
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Affiliation: | 1. East Malling Research Station, East Malling, ME19 6BJ, Maidstone, Kent, U. K.
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Abstract: | The plant growth retardant paclobutrazol, (PP333) (2RS, 3RS)-1-(4-chlorophenyl)-4,4-dimethyl-2-(1,2,4-triazol-1-yl)pentan-3-ol, inhibits specifically the three steps in the oxidation of the gibberellin-precursorent-kaurene toent-kaurenoic acid in a cell-free system fromCucurbita maxima endosperm. The KI50 for this inhibition is 2×10?8 M. The KI50 values for the separated2S, 3S, and2R, 3R enantiomers of paclobutrazol in this system are 2×10?8 M and 7×10?7 M, respectively. A cell-free preparation from immatureMalus pumila embryos convertsent-kaurene to gibberellin A9, whereas no conversion occurs in a similar preparation fromMalus endosperm. The conversion ofent-kaurene by the embryo preparation is inhibited by paclobutrazol with KI50 values for the2S,3S and2R,3R enantiomers of 2×10?8 M and 6×10?8 M, respectively. |
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