Metabolism of [3H]gibberellin A4 in somatic suspension cell cultures of carrot

The native gibberellin A₄ (GA₄), in radioactive form ([1,2-³H]GA₄, 1.06 Ci/mmol), was fed to carrot somatic cell cultures (suspension and immobilized cell systems) and its metabolism over a 48 hr period was investigated. It was found that the [³H]GA₄ was metabolized to at least two GAs, [³H]GA₁ and [³H]GA₈, six GA glucosyl conjugates, [³H]GA₁-0(3)-glucoside, [³H]GA₁-0(13)-glucoside, [³H]GA₁-glucosyl ester, [³H]GA₄-glucoside, [³H]GA₄-glucosyl ester, a [³H]GA₈ glucosyl conjugate(s) and a previously unknown [³H]GA₁ glucosyl conjugate ([³H]GA₁-0(3,13)-diglucoside-like compound). The GA₁-diglucoside-like compound was found only in extracts of cells and was present in significant amounts (33 % of total extractable radioactivity). All other metabolites were present in both cells and medium. For extracts of the medium, no differences between the suspension and immobilized cultures existed in types of [³H]GA₄ metabolites although quantitative differences were apparent.     

Gibberellin metabolism in excised lettuce hypocotyls: Response to GA9 and the conversion of [3H]GA9

Elongation growth and gibberellin (GA₉) metabolism in excised hypocotyls of lettuce (Lactuca sativa L. cv. Arctic) were investigated. Exogenously supplied GA₉ stimulates elongation of hypocotyl sections and this response is intermediate between that elicited by GA₁ or GA₂₀ and GA_4/7 mixture. Although uptake of radioactivity from [³H]GA₉ increases with time, this gibberellin does not accumulate in the tissue but is rapidly converted to a compound with HPLC properties resembling those of [³H]GA₂₀. After 2 h incubation in [³H]GA₉, the presumptive GA₂₀ represents 90% of the acidic ethyl acetate-soluble radioactivity in the tissue. Radioactivity is also associated with an acidic butanol-soluble fraction containing two components resolvable by HVE. The major component is similar in electrophoretic properties to a GA-glucosyl ether while the other compares to a GA-glucosyl ester. Conversion of [³H]GA₉ to its [³H]GA₂₀-like metabolite is reduced by addition of carrier GA₉ or GA_4/7 at concentrations as low as 1 M, while GA₁, GA₃ and L-proline are without effect. Formation of the GA₂₀-like compound can be blocked by the addition of 2,2-dipyridyl, and this inhibitory effect of dipyridyl can be reversed by addition of Fe²⁺. At 200 M dipyridyl, elongation growth as well as [³H]GA₉ metabolism are reduced by 80%. The relationship of the metabolism of GA₉ to the growth response is discussed.Abbreviations AB butanol-soluble - AE ethyl-acetate-soluble - GA gibberellin - GA₁, GA₄ gibberellin A₁, gibberellin A₄, etc. - TLC thin layer chromatography - HPLC high performance liquid chromatography - HVE high voltage electrophoresis     

Metabolism of [H]Gibberellin A(5) by Immature Seeds of Apricot (Prunus armeniaca L.)

Immature seeds of apricot (Prunus armeniaca L.) were fed the native gibberellin A₅ (GA₅) as 1- and 1,2-[³H]GA₅ (5.3 Curies per millimole to 16 milliCuries per millimole) at doses (42 nanograms to 10.6 micrograms per seed) 2 to 530 times the expected endogenous level. After 4 days of incubation, seeds were extracted and free [³H]GA-like metabolites were separated from the highly H₂O-soluble [³H]metabolites. For high specific activity feeds the retention times (Rts) of radioactive peaks were compared with Rts of authentic GAs on sequential gradient-eluted → isocratic eluted reversed-phase C₁₈ high performance liquid chromatography (HPLC) -radiocounting (RC). From high substrate feeds (530 and 230 × expected endogenous levels) HPLC-RC peak groupings were subjected to capillary gas chromatography-selected ion monitoring (GC-SIM), usually six characteristic ions. The major free GA metabolites of [³H] GA₅ were identified as GA₁, GA₃, and GA₆ by GC-SIM. The major highly water soluble metabolite of [³H]GA₅ at all levels of substrate GA₅ had chromatographic characteristics similar to authentic GA₁-glucosyl ester. Expressed as a percentage of recovered radioactivity, low substrate [³H]GA₅ feeds (2 × expected endogenous level) yielded a broad spectrum of metabolites eluting at the Rts where GA₁, GA₃, GA₅ methyl ester, GA₆, GA₂₂, GA₂₉ (17, 14, 1.6, 7, 1.1, 0.5%, respectively) and GA glucosyl conjugates of GA₁, GA₃, GA₅, and GA₈ (33, 11, 1, 0.1%, respectively) elute. Metabolites were also present at Rts where GA glucosyl conjugates of GA₆ and GA₂₉ would be expected to elute (8 and 0.1%, respectively). Only 5% of the radioactivity remained as GA₅. Increasing substrate GA₅ levels increased the proportion of metabolites with HPLC Rts similar to GA₁, GA₆, and especially GA₁ glucosyl ester, primarily at the expense of metabolites with HPLC Rts similar to GA₃, GA₃-glucosyl ester, and a postulated conjugate of GA₆. There was evidence that high doses of substrate GA₅ induced new metabolites which often, but not always, differed from GA₁, GA₃, and GA₆ in HPLC Rt. These same metabolites, when analyzed by GC-SIM yielded m/e ions the same as the M⁺ and other characteristic m/e ions of the above GAs, albeit at differing GC Rt and relative intensities.     

Metabolism of [1,2-3H]gibberellin A4 by epicotyls and cell-free preparations from Phaseolus coccineus L. seedlings

Cell-free systems were prepared from germinating seed and seedlings of Phaseolus coccineus. Gibberellin A₄ (GA₄)-metabolising activity was detected in vitro using preparations from roots, shoots and cotyledons of germinating seed, but only up to 24 h after imbibition. Cell-free preparations from cotyledons converted [³H]GA₄ to GA₁, GA₃₄, GA₄-glucosyl ester and a putative O-glucoside of GA₃₄, and, in addition converted [³H]GA₁ to GA₈. Preparations from embryo tissues contained 2-hydroxylase activity, converting [³H]GA₄ to GA₃₄ and [³H]GA₁ to GA₈.The presence of GA-metabolising enzymes was also indicated by in-vivo feeds of [³H]GA₄ to epicotyls of intact 4-d-old seedlings, which resulted in the accumulation of GA₁, GA₈, GA₃-3-O-glucoside, GA₄-glucosyl ester, GA₈-2-O-glucoside and a putative O-glucoside of GA₃₄. Gibberellin A₁ was the first metabolite detected, 15 min after application of [³H]GA₄, but after 24 h most of the label was associated with GA₈-2-O-glucoside. Over 90% of the recovered radioactivity was found in the shoot. Within the shoot, movement was preferentially acropetal, and was not dependent upon metabolism of the applied [³H]GA₄.Abbreviations DEAE diethylaminoethyl - GA_n gibberellin A_n - GPC gel permeation chromatography - HPLC-RC high performance liquid chromatography-radio counting - S-1 1000·g supernatant - UDP uridine 5-diphosphate     

Interconversion of gibberellin A4 to gibberellins A1 and A34 by dwarf rice,cultivar Tan-ginbozu

Summary Interconversion of GA₄ to GA₁ and GA₃₄ occurred within 24 h of application of 1,2-[³H]-GA₄ to seedlings of dwarf rice, cv. Tan-ginbozu. Identification was made by direct comparison of the trimethylsilyl ether derivatives of the methyl esters of Silica-gel partition-column fractions on gas-liquid radiochromatography with derivatized GA₁ and GA₃₄ standards on three columns: 2% QF-1, 2% SE-30, and 1% XE-60. GA₂, an artifact of the purification and chromatography system, may also be formed by the plant. The conversions from GA₄ to GA₁ and GA₃₄ are single hydroxylations. At least two unidentified radioactive products were also formed by the plant. Interconversions were in the order of 0.3 to 0.8% of applied [³H]-GA₄.Abbreviations GA gibberellin - GLC gas-liquid chromatography - GLRC gasliquid radiochromatography - TMSMe trimethylsilyl ether of methyl ester - TLC thin-layer chromatography     

Identification of gibberellin A9 methyl ester as a natural substance regulating formation of reproductive organs in Lygodium japonicum

Prothallia of Lygodium japonicum (Thunb.) Sw. were aseptically cultured under white light in a mineral solution. Solvent fractionation of the resultant culture medium and subsequent preparative thinlayer chromatography yielded a fraction that induced antheridium formation and inhibited archegonium formation. Combined gas chromatography-selected ion monitoring analysis of this fraction confirmed the presence of gibberellin A₉ methyl ester (GA₉-me) as an antheridiogen and an inhibitor of archegonium formation. Exogenously applied [³H]GA₉ was rapidly converted to [³H]GA₉-me in the prothallial tissue. Authentic GA₉-me was active to 10^-10M in antheridium formation and to 10^-9M in the inhibition of archegonium formation.Abbreviations GAs gibberellins - GA_n gibberellin A_n - GA_n me, gibberellin A_n methyl ester - TLC thin-layer chromatography - GCSIM Combined gas chromatography-selected ion monitoring     

Internode length in Pisum

The influence of the Na and Le genes in peas on gibberellin (GA) levels and metabolism were examined by gas chromatographic-mass spectrometric analysis of extracts from a range of stem-length genotypes fed with [¹³C, ³H]GA₂₀. The substrate was metabolised to [¹³C, ³H]GA₁, [¹³C, ³H]GA₈ and [¹³C, ³H]GA₂₉ in the immature, expanding apical tissue of all genotypes carrying Le. In contrast, [¹³C, ³H]GA₂₉ and, in one line, [¹³C, ³H]GA₂₉-catabolite, were the only products detected in plants homozygous for the le gene. These results confirm that the Le gene in peas controls the 3-hydroxylation of GA₂₀ to GA₁. Qualitatively the same results were obtained irrespective of the genotype at the Na locus. In all Na lines the [¹³C, ³H]GA₂₀ metabolites were considerably diluted by endogenous [¹²C]GAs, implying that the metabolism of [¹³C, ³H]GA₂₀ mirrored that of endogenous [¹²C]GA₂₀. In contrast, the [¹³C, ³H]GA₂₀ metabolites in na lines showed no dilution with [¹²C]GAs, confirming that the na mutation prevents the production of C₁₉-GAs. Estimates of the levels of endogenous GAs in the apical tissues of Na lines, made from the ¹²C:¹³C isotope ratios and the radioactivity recovered in respective metabolites, varied between 7 and 40 ng of each GA per plant in the tissue expanded during the 5 d between treatment with [¹³C, ³H]GA₂₀ and extraction. No [¹²C]GA₁ and only traces of [¹²C]GA₈ (in one line) were detected in the two Na le lines examined. These results are discussed in relation to recent observations on dwarfism in rice and maize.Abbreviations GA_n gibberellin A_n - GC-MS gas chromatography-mass spectrometry - HPLC high-pressure liquid chromatography     

Quantitation of gibberellins and the metabolism of [3H]gibberellin A1 during somatic embryogenesis in carrot and anise cell cultures

In a carrot (Daucus carota L.) cell line lacking the ability to undergo somatic embryogenasis, and in carrot and anise (Pimpinella anisum L.) cell lines in which embryogenesis could be regulated by presence or absence of 2,4-dichlorophen-oxyacetic acid (2,4-D), in the medium (+2,4-D=no embryogenesis,-2,4-D=embryo differentiation and development), the levels of endogenous gibberellin(s) (GA) were determined by the dwarfrice bioassay, and the metabolism of [³H]GA₁ was followed. Embryos harvested after 14 d of subculture in-2,4-D had low levels (0.2–0.3 g g^-1 dry weight) of polar GA (e.g. GA₁-like), but much (3–22 times) higher levels of less-polar GA (GA_4/7-like); GA₁, GA₄ and GA₇ are native to these cultures. Conversely, the undifferentiated cells in a non-embryogenic strain, and proembryos of an embryogenic strain (+2,4-D) showed very high levels of polar GA (2.9–4.4 g g^-1), and somewhat reduced levels of less-polar GA. Cultures of anise undergoing somatic embryo development (-2,4-D) metabolized [³H]GA₁ very quickly, whereas proembryo cultures of anise (+2,4-D) metabolized [³H]GA₁ slowly. The major metabolites of [³H]GA₁ in anise were tentatively identified as GA₈-glucoside (24%), GA₈ (15%), GA₁-glucoside (8%) and the ¹⁽¹⁰⁾GA₁-counterpart (2%). Thus, high levels of a GA₁-like substance and a reduced ability to metabolize GA₁ are correlated with the absence of embryo development, while lowered levels of GA₁-like substance and a rapid metabolism of GA₁ into GA₈ and GA-conjugates are correlated with continued embryo development. Exogenous application of GA₃ is known to reduce somatic embryogenesis in carrot cultures; GA₄ was found to have the same effect in anise cultures. Thus, a role (albeit negative) in somatic embryogenesis for a polar, biologically active GA is implied.Abbreviations 2,4-D 2,4-dichlorophenoxyacetic acid - GA gibberellin(s) or gibberellin-like substances - GC-RC gas chromatography-radiochromatogram counting - HPLC high-presare liquid chromatography - Rt retention time - TLC thinlaver chromatography     

Metabolic formation and occurrence of gibberellin A1-3-0-β-D-glucopyranoside in immature fruits of Phaseolus coccineus L.

Endogenous pools of presumptive gibberellin (GA) glucosyl conjugates of Phaseolus coccineus were metabolically labelled by feeding of [³H]GA₁ to immature fruits. The [³H]GA₁ glucoside fraction was isolated and the main constituent tentatively identified by enzymic hydrolysis, ion exchange chromatography and elution volume on HPLC-RC as GA₁-3-0--D-glucopyranoside.     

Growth and gibberellin-A1 metabolism in normal and gibberellin-insensitive (Rht3) wheat (Triticum aestivum L.) seedlings

Growth parameters were determined for tall (rht3) and dwarf (Rht3) seedlings of wheat (Triticum aestivum L.). Plant statures and leaf length were reduced by 50% in dwarfs but root and shoot dry weights were less affected. Leaves of dwarf seedlings had shorter epidermal cells and the numbers of cells per rank in talls and dwarfs matched the observed relationships in overall length. Talls grew at twice the rate of dwarfs (2.3 compared with 1.2 mm h^-1). [³H]Gibberellin A₁ ([³H]GA₁) was fed to seedlings via the third leaf and metabolism was followed over 12 h. Immature leaves of tall seedlings transferred radioactivity rapidly to compounds co-chromatographing with [³H]gibberellin A₈ ([³H]GA₈) and a conjugate of [³H]GA₈, whereas leaves of dwarf seedlings metabolised [³H]GA₁ more slowly. Roots of both genotypes produced [³H]GA₈-like material at similar rates. Isotopic dilution studies indicated a reduced 2-hydroxylation capacity in dwarfs, but parallel estimates of the endogenous GA pool size, obtained by radioimmunoassay, indicated a 12–15 times higher level of GA in the dwarf immature leaves. Dwarfing by the Rht3 gene does not appear to operate through enhanced, or abnormal metabolism of active gibberellins and the act of GA metabolism does not bear an obligate relationship to the growth response.Abbreviations GA_n gibberellin A_n - HPLC high-performance liquid chromatography     

Heterosis and the metabolism of gibberellin A20 in sorghum

The correlation between gibberellin (GA) metabolism and growth rate was investigated using two Sorghum bicolor inbred lines, Hegari and AT×623, and their heterotic F₁ hybrid. Previous studies have demonstrated that this hybrid is taller and has substantially greater shoot dry weights and leaf areas than either parental inbred. [³H]GA₂₀ was applied to the leaf whorl of seedlings and after 24 hours, plants were harvested and separated into roots, shoot cylinders containing the apical meristems, and leaf blades. Chromatographic analyses of metabolites indicated the conversions of [³H]GA₂₀ to [³H]GA_{1,8 and 29}. The conversion of [²H]GA₂₀ to [²H]GA₁ was demonstrated by gas chromatography-selected ion monitoring (GC-SIM). Putative glucosyl conjugates of all of the [³H]GAs were also produced and GA₈ was identified by GC-SIM following enzymic cleavage of the putative [³H]GA₈ glucosyl conjugate fraction. Comparing the genotypes, [³H]GA₂₀ metabolism was more rapid in the shoot cylinders of the hybrid than in the shoot cylinders from inbreds. In the hybrid samples, there was a three-fold increase in the putative conjugate(s) of [³H]GA₁ which was the principal metabolite, and increased production of [³H]GA₈ and the putative conjugates of [³H]GA₂₉ and [³H]GA₈. Conversely, levels of the remaining precursor, [³H]GA₂₀, and its putative conjugate(s) were reduced in the hybrid. The rate of GA₂₀ metabolism was thus positively correlated with growth rate across these sorghum genotypes. This correlation supports a promotive role of GA in the regulation of shoot growth and in the expression of heterosis (hybrid vigor) in sorghum.     

Metabolism of [3H]gibberellin A5 in developing pharbitis nil seeds

The native gibberellin A₅ (GA₅), as [1-³H]GA₅ (3.2 Ci/mmol) was fed to seed capsules (0.58 μCi/capsule) of Pharbitis nil cv Violet at the 2-week stage of development, and its metabolism in the seeds was investigated after 43 hr. Extractable radioactivity in free GA metabolites was 38%, with 56% in GA glucosyl conjugate-like substances. Only 2.5% of the extractable radioactivity remained as [³H]GA₅. Tentative identifications, based on comparisons with authentic standards after sequential chromatography on silica gel partition column → gradient-eluted C₁₈ HPLC → isocratic-eluted C₁₈ HPLC-radiocounting (RC), showed that [³H]GA₅ was converted to at least six free GAs, GA₁, GA₃, GA₆, GA₈, GA₂₂, GA₂₉, a GA₅ methyl ester-like metabolite, and at least twelve GA glucosyl conjugate-like substances, GA₅-glucoside (GA₅-G), GA₅-glucosyl ester (GA₅-GE), GA₁-O(3)-G, GA₁-O(13)-G, GA₁-GE, GA₃-O(3)-G, GA₃-O(13)-G, GA₃-GE, GA₆-G or GE, GA₈-O(2)-G, GA₂₂-G or GE and GA₂₉-O(2)-G. After lower specific activity feeds of [1,2-³H]GA₅ (74 mCi/mmol; 0.1 μCi/capsule) at approximately the same stage of development, the presence of GA₁, GA₃, GA₅, GA₆, GA₈ and GA₂₉ was further confirmed by sequential (after C₁₈ HPLC-RC) capillary gas chromatography-selected ion monitoring (GC-SIM), using six characteristic ions. However, for GA₂₂ only a trace of the parent ion was present at the appropriate retention time.     

Internode length in Zea mays L.

[¹³C, ³H]Gibberellin A₂₀ (GA₂₀) has been fed to seedlings of normal (tall) and dwarf-5 and dwarf-1 mutants of maize (Zea mays L.). The metabolites from these feeds were identified by combined gas chromatography-mass spectrometry. [¹³C, ³H]Gibberellin A₂₀ was metabolized to [¹³C, ³H]GA₂₉-catabolite and [¹³C, ³H]GA₁ by the normal, and to [¹³C, ³H]GA₂₉ and [¹³C, ³H]GA₁ by the dwarf-5 mutant. In the dwarf-1 mutant, [¹³C, ³H]GA₂₀ was metabolized to [¹³C, ³H]GA₂₉ and [¹³C, ³H]GA₂₉-catabolite; no evidence was found for the metabolism of [¹³C, ³H]GA₂₀ to [¹³C, ³H]GA₁. [¹³C, ³H]Gibberellin A₈ was not found in any of the feeds. In all feeds no dilution of ¹³C in recovered [¹³C, ³H]GA₂₀ was observed. Also in the dwarf-5 mutant, the [¹³C]label in the metabolites was apparently undiluted by endogenous [¹³C]GAs. However, dilution of the [¹³C]label in metabolites from [¹³C, ³H]GA₂₀ was observed in normal and dwarf-1 seedlings. The results from the feeding studies provide evidence that the dwarf-1 mutation of maize blocks the conversion of GA₂₀ to GA₁.Abbreviations GA_n gibberellin A_n - GC-MS combined gas chromatography-mass spectrometry - HPLC high-performance liquid chromatography - RP reverse phase     

Effect of 2-chloroethyltrimethyl ammonium chloride on tuberization and endogenous GA3 in roots of potato cuttings

Cuttings of potato shoots treated with the plant growth retardant 2-chloroethyltrimethyl ammonium chloride (CCC) form tubers earlier and have less biologically-active gibberellin (GA)-like substances in the roots than control cuttings. The major GA-like substance in roots of potato cuttings was identified as GA₃ by gas-chromatography-mass spectrometry (GC-MS). The content of GA₃ in roots of control cuttings, estimated by GC-MS-selected ion monitoring (SIM) using [17, 17-²H]GA₃ as a quantitative internal standard, was 38.8 ng per g fresh weight (fw), and in roots of CCC-treated cuttings, in which tuberization was promoted, was 0.6 ng per g fw. Gibberellin A₁, GA₈ and GA₂₀ were also indicated as minor components of roots from both control and CCC-treated cuttings. The comparatively high GA₃ content in roots of control cuttings might be the root factor responsible for delaying tuberization in potato.Abbreviations CCC 2-chloroethyltrimethyl ammonium chloride - dw dry weight - EtOAc ethyl acetate - GA gibberellin - GC-MS-SIM gas chromatography-mass spectrometry-selected ion monitoring - HPLC high performance liquid chromatography - IAA indole-3-acetic acid - KRI Kovats' retention index - MeOH methanol - MeTMSi methyl ester trimethylsilyl ether - NAA naphthalene acetic acid - SD short day(s) - 2,4-D 2,4-dichlorophenoxy acetic acid     

Uptake and metabolism of radioactive gibberellins by barley aleurone layers

Summary When aleurone layers were treated with labeled gibberellin A₁ (³H-GA₁), gibberellin A₅ (³H-GA₅) and the methyl ester of ³H-GA₅ (³H-GA₅-ME), radioactivity was accumulated by the tissue for a period of 20–30 h. After this time, radioactivity was released into the medium. Concomitantly, ribonuclease was also liberated by the tissue. The radioactivity accumulated by aleurone layers was associated with polar metabolites of the respective GAs, and the extent of extent of accumulation was a function of the degree of GA metabolism (GA₅-ME>GA₅>GA₁). Accumulation of radioactivity was inhibited in the cold and by the metabolic poisons NaF and dinitrophenol. This was thought to be due to inbition of GA metabolism. The accumulation of ³H-GA₁ in aleurone tissue did not reach saturation when unlabeled GA₃ up to 10^-2 M was added to the incubation medium.Abbreviations GA gibberellin - GA₅ ME, gibberellin A₅ methyl ester - RNase ribonuclease     

Interaction of [3H]gibberellin A1 with a sub-cellular fraction from lettuce (Lactuca sativa L.) hypocotyls

The relationship between protein synthesis and the incorporation of [³H]gibberellin A₁ ([³H]GA₁) into a 2,000xg pelletable (2KP) fraction from lettuce (Lactuca sativa L.) hypocotyl sections has been investigated. Concentrations of D-2-(4-methyl-2,6-dinitroanilino)-N-methylpropionamide (MDMP) between 10^-7 M and 10^-4 M caused increasing inhibition of growth, 2KP labelling and incorporation of [¹⁴C]leucine into soluble protein. Growth and 2KP radioactivity were highly correlated (r=0.996). Transfer to MDMP early or late in the course of GA response caused reductions in both growth and incorporation into the 2KP fraction. Exposure to the inhibitor had more effect at 4 h than at 20 h. The proportions of alkali-soluble and insoluble radioactivity in the 2KP fraction were also altered by this treatment. The implications of these findings are discussed.Abbreviations GA₁ gibberellin A₁ - MDMP D-2-(4-methyl-2,6-dinitroanilino)-N-methylpropionamide - 2KP a2,000xg pelletable fraction     

Metabolism of [3H] Gibberellin A5 in Cell Suspension Cultures of Pharbitis nil

Gibberellin A₅ (GA₅), a native GA of immature seeds of Pharbitis nil, was fed to Pharbitis nil cell suspension cultures as [C-l, ³H] GA₅ (3.1 Ci/mmol), and its metabolism over a 48 hr period was investigated. Radioactivity in free GA metabolites was 13.1%, with 79.9% in GA glucosyl conjugate-like metabolites. Only 7.0% of the radioactivity remained as [³H] GA₅. Tentative identifications were based on comparison with retention times of authentic free GAs and/or glucosyl conjugates after sequential chromatography on Si gel partition column → gradient-eluted C18 HPLC-radiocounting (RC) → isocratic-eluted C18 HPLC-RC, and showed that [³H] GA₅ was converted to [³H] GA₁ (2%), [³H] GA₃ (4%), [³H] GA₆ (2%), [³H] GA₂₂ (1%) and their glucosyl conjugates, and also to [³H] GA₈ glucoside, and [³H] GA₅ glucosyl conjugates. The major conjugate-like substances were [³H] GA₁ and [³H] GA₃ glucosyl esters, at 15% and 34%, respectively, of the total extractable radioactivity.     

Metabolism of Tritiated Gibberellins in d-5 Dwarf Maize: I. In Excised Tissues and Intact Dwarf and Normal Plants

Metabolism of [³H]gibberellin A₁ ([³H]GA₁) was followed in intact seedlings and excised apices and leaf tissue of both dwarf and normal (tall) plants of d-5 maize (Zea mays L.). The three metabolites produced were tentatively identified as [³H]GA_s, [³H]GA_s-glucoside ([³H]GA_s-glu), and [³H]GA₁-X, an unknown.     

The identification and metabolism of GA9 and its metabolites in seed coats and shoots of pea,line G2

[³H]gibberellin A₉ was applied to shoots or seed parts of G2 pea to produce radiolabeled metabolites. These were used as markers during purification for the recovery of endogenous GA₉ and its naturally occurring metabolites. GA₉ and its metabolites were purified by HPLC, derivatized and examined by GC-MS. Endogenous GA₉, GA₂₀, GA₂₉ and GA₅₁ were identified in pea shoots and seed coats. GA₅₁-catabolite and GA₂₉-catabolite were also detected in seed coats. GA₇₀ was detected in seed coats following the application of 1 g of GA₉. Applied [³H]GA₉ was metabolized through both the 13-hydroxylation and 2-hydroxylation pathways. Labeled metabolites were tentatively identified on the basis of co-chromatography on HPLC with endogenous compounds identified by GC-MS. In shoots [³H]GA₅₁ and [³H]GA₅₁-catabolite were the predominant metabolites after 6 hrs, but by 24 hrs there was little of these metabolites remaining, while [³H]GA₂₉-catabolite and an unidentified metabolite predominated. In seed coats [³H]GA₅₁ was the initial product, later followed by [³H]GA₅₁-catabolite and an unidentified metabolite (different from that in shoots), with lesser amounts of [³H]GA₂₀, [³H]GA₂₉ and [³H]GA₂₉-catabolite. [³H]GA₇₀ was a very minor product in both cases. [³H]GA₉ was not metabolized by pea cotyledons.Edited by T.J. Gianfagna.Author for correspondence