METABOLISM OF ALLENIC ANALOGS OF ABSCISIC-ACID

We have already reported that some allenic analogues of abscisic acid inhibited growth of duckweed (Lemna gibba and L. paucicostata) in axenic culture, and other plants. The duckweed produced turion-like structures in the presence of these analogues when growing in continuous light. The induction of turions has hitherto been caused only by ABA or short photoperiods. Deuteriated, allenic analogues were supplied to axenic cultures of the L. gibba, for seven days and the ABA in the media and in the fronds was found to contain deuterium, thereby establishing that allenic analogues had been converted into ABA. The oxygen atom at C-1', the addition of which is required during the formation of ABA from the allenic analogues, is derived from the medium. This was determined by mass spectrometry of the ABA formed in experiments in which the L. gibba fronds had been supplied with [H-2(2)]AB allenic alcohol acetate and grown in [O-18]H2O (30 atoms %). The ABA was found to contain O-18 at C-1'. The 2-trans allenic AB alcohol acetate was converted into 2-trans-ABA and 2-trans-AB aldehyde. Thus the growth inhibition and morphological effects observed when the plants were grown in the presence of the allenic analogues can be attributed to the ABA formed from them.