Effects of 17-alkyl-16,17-dihydrogibberellin A(5) derivatives on growth and flowering in Lolium temulentum

Several gibberellins in which the 16-methyl group of the 16-epimers of dihy dro-GA(5) had been replaced by ethyl, n-propyl and n-butyl were prepared an d tested at doses of 1, 5 or 25 mu g per plant for their effects on stem gr owth and flowering of the grass Lolium temulentum. The ethyl and n-propyl d erivatives were most inhibitory of elongation, the exo-isomers being more a ctive than the endo-forms. While both isomers of dihydro-GAS promoted flowe ring, among the 17-alkyl analogues, only the exo-ethyl derivative showed si gnificant activity. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.