Inhibition of gibberellin biosynthesis by paclobutrazol in cell-free homogenates ofCucurbita maxima endosperm andMalus pumila embryos |
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| Authors: | Peter Hedden and Jan E Graebe |
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| Institution: | (1) East Malling Research Station, East Malling, ME19 6BJ Maidstone, Kent, U. K.;(2) Present address: Long Ashton Research Station, University of Bristol, Long Ashton, BS18 9AF Bristol, U.K.;(3) Present address: Pflanzenphysiologisches Institut der Universität, Untere Karspüle 2, D-3400 Göttingen |
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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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