Use of an Acylcyclohexanedione Growth Retardant, LAB 198 999, to Determine Whether Gibberellin A20 Has Biological Activity per se in Dark-Grown Dwarf (le5839) Seedlings of Pisum sativum

Dwarf (le(5839)) seedlings of Pisum sativum respond to gibberellin A(20) (GA(20)) in the dark, although the same dosage of GA(20) applied to light-grown le(5839) seedlings elicits no growth response. The acylcyclohexanedione growth retardant, LAB 198 999, which is known to inhibit gibberellin oxidation and in particular 3beta-hydroxylation such as the conversion of GA(20) to GA(1), also inhibits the growth response of dark-grown dwarf (le(5839)) seedlings to GA(20). Thus, the biological activity of GA(20) in the dark appears to be a consequence of its conversion to GA(1), even though it is known from studies with light-grown seedlings that the le mutation reduces the conversion of GA(20) to GA(1).