An Analysis of Seed Development inPisum sativum

Wang, T. L., Cook, S. K., Francis, R. J., Ambrose, M. J. and Hedley, C. L. 1987. An analysis of seed development in Pisum sativum. VI. Abscisic acid accumulation.—J. exp. Bot. 38: 1921-1932. The abscisic acid (ABA) content of wrinkled (rr) pea seed tissues has been quantified during development using multiple-ion-monitoring combined gas chromatography-mass spectrometry and a deuterated internal standard. The level of ABA in the embryo generally increased with increasing cotyledon fresh weight while that in the testa showed a distinct maximum at the time of maximum endosperm 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, the first maximum following the maximum growth rate of the testa and the second that of the embryo. The biphasic distribution of ABA in the pea seed was confirmed using a second pea genotype, near-isogenic to the first except for the r locus, and by the analysis of individual seeds using a radioimmunoassay for ABA. The first maximum was composed mainly of a testa component and the second mainly of an embryo component. When plants were grown in different environments, wrinkled seeds were found to contain slightly more ABA than round (RR) but this was only significant late in development. Immature seeds were capable of metabolizing l'-deoxy ABA to ABA, as deter mined by incorporation of either 3H or 2H, and the metabolite was present mainly in the testa. The production of ABA in pea seeds is discussed in relation to the development of the different seed tissues. Key words—Abscisic acid, peas, seed development. Correspondence to: John Innes Institute, Colney Lane, Norwich NR4 7UH, U.K.