title: An investigation of the gibberellins of Pisum sativum L
Creators: name: Davies, John Keith
Publisher: name: University of Glasgow
Year: 1984

description: An investigation was made of the endogenous GAs of young Pisum sativum seedlings, and of the metabolism of [3H]GAg, [3H]GA12 aldehyde, [3H]GA20 and [3H]GA20 by Pisum seedlings. An extract of ten-day-old light-grown seedlings of the tall cultivar Alaska was purified and then separated by HPLC into seventy fractions, which were analysed using three bioassays and a GA1 radioimmunoassay. Active fractions were subsequently analysed by GC-MS, Mass spectra of GA20 and GA29 were obtained. GC-MS failed to detect GA1 in a HPLC fraction that had chromatographic and assay properties similar to those of GA1. GC-MS did however detect the presence of a novel GA-like compound in this fraction. Although the identity of this component was not determined its mass spectrum contained ions characteristic of the presence of a 13-hydroxyl group. Extracts of eight-day-old shoots from light- and dark- grown seedlings of the tall cultivar Alaska and the dwarf cultivars Pleteor and Progress No.9 were each separated into 35 fractions by HPLC, and each fraction analysed for the presence of GA-like substances using a GA1 radioimmunoassay. Light-grown shoots of all three cultivars appeared to contain similar GA-like substances, at least four being detected. The amount of GA2q in light grown shoots was estimated and varied from 70 to 330 pg seedling -1 (ca. 0.4 to 1.6 ng g.f.wt-1). These estimates are corrected for the recovery of internal standards in the extracts and for the cross-reactivity of Gl20 in the GA1 RIA. Dark-grown shoots contained much lower amounts of all the GA-like substances detected, regardless of whether the amount was expressed on a per seedling or on a per unit weight basis. Tritiated products from feeds of [3H]GAs to seedlings were analysed by HPLC-RC. Some of the [3H]GA14 metabolites were also analysed by GC-MS. [3H]GA9 was metabolised extensively by light- grown seedlings of the cultivar Alaska, Meteor and Progress No.9, and also by dark-grown seedlings of the cultivar Alaska. At least twenty seven metabolites were detected, but only GA20 and possibly GA29 were identified. The pattern of metabolism appeared identical in cv. Meteor and in cv. Progress No.9, and this was very similar to the spectrum of metabolites observed from light- and dark- grown seedlings of the cultivar Alaska. Only low amounts of a single possible metabolite of [3H]GA20 were detected. This putative metabolite was present in similar amounts in extracts of light-grown shoots of the cultivars Alaska, Meteor and Progress No.9. The metabolite was not identified but was not GA1 or GA8, and probably not GA29 or GA29 catabolite. At least fourteen metabolites were observed from a feed of [3H]GA14 to young light-grown seedlings of the cultivar Alaska. One product was identified by GC-FIS as GA18, but the other metabolites were not identified, although HPLG and GC-POS analysis showed some of them to be distinct from a range of GAs, including GA1, GA8, GA18, GA23,GA28,GA38 and GA42, which were identified by Durley st al.(1974a,b) as products of [3H]GA14 fed to pea seedlings. [3H]GA12 aldehyde was converted to small amounts of number of products, but these were not distinguished from breakdown products observed in control extractions.