An Analysis of Seed Development in Pisum sativum: VI. ABSCISIC ACID ACCUMULATION

The abscisic acid (ABA) content of wrinkled (rr) pea seed tissueshas been quantified during development using multiple-ion-monitoringcombined gas chromatography-mass spectrometry and a deuteratedinternal standard. The level of ABA in the embryo generallyincreased with increasing cotyledon fresh weight while thatin the testa showed a distinct maximum at the time of maximumendosperm volume and the slowing in the growth of the testa.Pods contained relatively little ABA on a fresh weight basis.The total seed ABA content showed a biphasic distribution, thefirst maximum following the maximum growth rate of the testaand the second that of the embryo. The biphasic distributionof ABA in the pea seed was confirmed using a second pea genotype,near-isogenic to the first except for the r locus, and by theanalysis of individual seeds using a radioimmunoassay for ABA.The first maximum was composed mainly of a testa component andthe second mainly of an embryo component. When plants were grownin different environments, wrinkled seeds were found to containslightly more ABA than round (RR) but this was only significantlate in development. Immature seeds were capable of metabolizing17'-deoxy ABA to ABA, as determined by incorporation of either³H or ²H, and the metabolite was present mainly in the testa.The production of ABA in pea seeds is discussed in relationto the development of the different seed tissues. Key words: Abscisic acid, peas, seed development