This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via CrossRef Citing Articles via Google Scholar Google Scholar Articles by Rood, S. B. Articles by Koshioka, M. Search for Related Content PubMed PubMed Citation Articles by Rood, S. B. Articles by Koshioka, M. Agricola Articles by Rood, S. B. Articles by Koshioka, M.

Articles

Reversible Conjugation of Gibberellins In Situ in Maize ¹

Department of Biology, University of Calgary, Calgary, Alberta, Canada T2N 1N4

Gibberellins [³H]GA₄ (1.33 Curies per millimole) and [³H]GA₂₀ (2.36 Curies per millimole) were injected into the shanks of maize (Zea mays L.) cobs during rapid grain filling and mature seeds were subsequently harvested. Extracts of mature, dry seeds from 1980 feeds yielded only 20 to 30% of the ³H radioactivity in acidic, ethyl acetate-soluble form, and this was principally associated with the precursor, with lesser amounts of the major metabolite, [³H]GA₁ (putative identification based on sequential SiO₂ partition, and gradient-eluted reverse-phase C₁₈ high performance liquid chromatography [HPLC]). Most of the radioactivity in the dry seeds was associated with compounds having partition characteristics of, and co-chromatographing on, sequential SiO₂ partition and reverse-phase HPLC with glucosyl conjugates of the precursors (GA₄ or GA₂₀) and their probable major metabolite (GA₁). The majority of conjugate associated with the precursor GA₄ eluted coincidental with GA₄ glucoside. Subsequent acid or enzymic hydrolysis (-glucosidase or cellulase) yielded the free GAs, putative identification being based on isocratic HPLC of each ³H-labeled conjugate hydrolysis isocratic HPLC of the ³H-labeled hydrolysate. Upon imbibition of the seeds, radioactivity associated with the conjugate fraction decreased; concomitantly, statistically significant increases in levels of free [³H]GA-like compounds were observed. Although the specific ratios of GA-like and GA-glucosyl conjugate-like substances varied substantially across years, hybrids, and even, in different plants from the same hybrid, this `reversible conjugation' (i.e. apparent conjugation during seed maturation followed by release of the GA moiety during germination), was reproducible for [³H]GA₂₀ in seed from two maize hybrids produced over 2 years.

³ To whom requests for reprints should be sent.

¹ Supported by Natural Sciences and Engineering Research Council Grant A-2585 to R. P. P.