Fate of Radioactive Gibberellin A1 in Maturing and Germinating Seeds of Peas and Japanese Morning Glory

Abstract

Radioactive gibberellin A1 (3H-GA1) was injected into excised fruits of peas and Japanese morning g10ry. These were then grown in sterile culture to maturity and the label was fol10wed in the seeds during further deve10pment and subsequent germination. During deve10pment of both pea and morning-g10ry seeds a large part of the radioactivity became associated with the aqueous fraction, while another part of the 3H-GA1 was converted into 2 new, acidic, bio10gically active compounds, designated X1 and X2. A relatively small part of the neutral compounds could be converted back to 3h-GA1, X1, and X2 by means of mild acid hydrolysis. During germination of pea and morning-g10ry seeds, part of the bound compounds was released in the form of 3h-GA1, X1 and X2 while, particularly during rapid seedling growth, a further conversion of 3h-GA1, mainly to X1, took place. In pea seedlings, growth during the first 2 to 3 days after imbibition was not affected by Amo-1618, an inhibitor of gibberellin biosynthesis. This, in conjunction with the findings on the interconversions between free and bound 3h-GA1 suggests that, at least in peas, early seedling growth may at least partly be regulated by gibberellins released from a bound form which was formed during seed deve10pment.