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PubMed2002

Abscisic acid, phaseic acid and gibberellin contents associated with dormancy and germination in barley.

Analyses of abscisic acid (ABA), ent-kaurenoids and gibberellins (GAs) showed that there were major changes in the contents of these compounds associated with germination of after-ripened barley (Hordeum vulgare cv. Schooner and cv. Proctor) grain but not in hydrated dormant grain. Embryos from dormant and after-ripened dry grain contained similar amounts of ABA, of ent-kaurenoids and of GAs, determined by gas chromatography-mass spectrometry-selected ion monitoring. In embryos of after-ripened grain, ABA content decreased rapidly after hydration and ABA appeared to be metabolized (inactivated) to phaseic acid (PA) rather than diffusing into the endosperm or the surrounding medium as previously thought. Similar changes in ABA occurred in hydrated dormant grain during germination in darkness. Accumulation of ent-kaurenoids and GAs, including GA1, the first biologically active GA in the early 13-hydroxylation biosynthetic pathway, occurred to a much greater extent in after-ripened than in dormant grain and these changes occurred mainly after 18 h of hydration when ABA had already decreased and germination was occurring. The block in ent-kaurenoid and GA synthesis in dormant grain appeared to occur prior to ent-kaurene in the biosynthetic pathway. These results are consistent with the view that ABA is the primary effector of dormancy and that after-ripening involves the development of the ability to reduce the amount of ABA quickly following hydration. Accumulation of GAs does not appear to be causally related to loss of dormancy but it does appear to be related to germination.

Journal Article↗

PubMed2002

Gibberellin regulates post-microsporogenesis processes in petunia anthers.

Previous studies have suggested that gibberellins (GAs) are produced in petunia anthers and transported to the corolla to induce growth and pigmentation. In this work, we studied the role of GA in the regulation of anther development. When petunia plants were treated with the GA-biosynthesis inhibitor paclobutrazol, anther development was arrested. Microscopic analysis of these anthers revealed that paclobutrazol inhibits post-meiotic developmental processes. The treated anthers contained pollen grains but the connective tissue and tapetum cells were degenerated. A similar phenotype was obtained when the Arabidopsis GA-signal repressor, SPY, was over-expressed in transgenic petunia plants, i.e. anther development was arrested following microsporogenesis. The expression of the GA-induced gene, GIP, can be used in petunia as a molecular marker to study GA responses. GA3 treatment of young anthers promoted, and paclobutrazol inhibited, GIP expression, suggesting that the hormone controls the natural activation of the gene in the anthers. Analyses of GIP expression during anther development revealed that the gene is induced only after microsporogenesis. This observation further suggests a role for GA in the regulation of post-meiotic processes during petunia anther development.

Journal Article↗

PubMed2003

Spiral growth and cell wall properties of the gibberellin-treated first internodes in the seedlings of a wheat cultivar tolerant to deep-sowing conditions.

The Hong Mang Mai wheat cultivar is tolerant to deep-sowing conditions because it has an elongated first internode that is sensitive to gibberellin (GA3). The cells in the GA-treated first internodes were approximately 4.2 mm long, twice as long as the untreated Hong Mang Mai first internode cells. The elongation of the first internode of Hong Mang Mai, particularly when treated with GA3, was accompanied by remarkable spiral growth. In contrast, the first internodes of the GA-insensitive cultivar Norin 10 did not exhibit GA3-induced elongation or spiral growth. The walls of the first internode cells of GA3-treated Hong Mang Mai seedlings showed increased extensibility and higher (1-->3), (1-->4)-beta-d-glucanase activity, autolysis and glucan contents than the cell walls of untreated Hong Mang Mai first internodes. The changes in the cell wall extensibility due to GA3 treatment correlated strongly with the GA3-induced changes in cell wall glucan content, autolysis, and glucanase activity. GA3-treated Hong Mang Mai seedlings showed elevated expression of Glucanase EI gene in the first internode compared to GA3-treated Norin 10. Thus, GA aids first internode elongation in Hong Mang Mai by enhancing glucan turnover and thus increasing cell wall loosening. The spiral growth of the first internode also helps the plant elongate against soil resistance, thereby promoting the deep-sowing tolerance of this cultivar.

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PubMed2000

Induction of dwarfism in transgenic Solanum dulcamara by over-expression of a gibberellin 20-oxidase cDNA from pumpkin.

The gibberellin (GA) 20-oxidase (CmGA20ox1) from immature pumpkin seed produces predominantly inactive tricarboxylic acid GAs. We expressed CmGA20ox1 under the control of the CaMV 35S promoter in Solanum dulcamara to assess the usefulness of this gene for reducing GA content in transgenic plants. All transgenic plants obtained were semi-dwarfs with smaller, deep-green leaves and highly pigmented stems compared to the wild-type. Such transformants flowered earlier than the wild-type plants and produced more fruit and more seeds per fruit. The transgene was efficiently expressed, producing high levels of CmGA20ox1 transcript and protein. Furthermore, the concentration of GA(1) was reduced in leaves of the transformants to approximately 20% or less of that in the wild-type and to about 40% or less in stems. The concentrations of other 13-hydroxylated GAs were also reduced, except for the tricarboxylic acid, GA(17), which accumulated in the transformants due to 13-hydroxylation of GA(25). By contrast, the concentrations of non-13-hydroxylated GAs, GA(4) and GA(34), were not consistently reduced, indicating that the effect of expressing the pumpkin gene may not be predictable. Transcript abundance for a native GA 20-oxidase gene was higher in the leaves and stems of S. dulcamara transformed with the pumpkin gene than in wild-type, reflecting the feedback control of 20-oxidase gene expression that serves as a homeostatic mechanism for GAs.

Base Sequence↗

PubMed2002

Semidwarf (sd-1), "green revolution" rice, contains a defective gibberellin 20-oxidase gene.

The introduction of semidwarf rice (Oryza sativa L.) led to record yield increases throughout Asia in the 1960s. The major semidwarfing allele, sd-1, is still extensively used in modern rice cultivars. The phenotype of sd-1 is consistent with dwarfism that results from a deficiency in gibberellin (GA) plant growth hormones. We propose that the semidwarf (sd-1) phenotype is the result of a deficiency of active GAs in the elongating stem arising from a defective 20-oxidase GA biosynthetic enzyme. Sequence data from the rice genome was combined with previous mapping studies to locate a putative GA 20-oxidase gene (Os20ox2) at the predicted map location of sd-1 on chromosome 1. Two independent sd-1 alleles contained alterations within Os20ox2: a deletion of 280 bp within the coding region of Os20ox2 was predicted to encode a nonfunctional protein in an indica type semidwarf (Doongara), whereas a substitution in an amino acid residue (Leu-266) that is highly conserved among dioxygenases could explain loss of function of Os20ox2 in a japonica semidwarf (Calrose76). The quantification of GAs in elongating stems by GC-MS showed that the initial substrate of GA 20-oxidase activity (GA53) accumulated, whereas the content of the major product (GA20) and of bioactive GA1 was lower in semidwarf compared with tall lines. We propose that the Os20ox2 gene corresponds to the sd-1 locus.

Amino Acid Sequence↗

PubMed2001

Cloning and functional analysis of two gibberellin 3 beta -hydroxylase genes that are differently expressed during the growth of rice.

We have cloned two gibberellin (GA) 3 beta-hydroxylase genes, OsGA3ox1 and OsGA3ox2, from rice by screening a genomic library with a DNA fragment obtained by PCR using degenerate primers. We have used full-scan GC-MS and Kovats retention indices to show function for the two encoded recombinant fusion proteins. Both proteins show 3 beta-hydroxylase activity for the steps GA(20) to GA(1), GA(5) to GA(3), GA(44) to GA(38), and GA(9) to GA(4). In addition, indirect evidence suggests that the OsGA3ox1 protein also has 2,3-desaturase activity, which catalyzes the steps GA(9) to 2,3-dehydro-GA(9) and GA(20) to GA(5) (2,3-dehydro GA(20)), and 2 beta-hydroxylase activity, which catalyzes the steps GA(1) to GA(8) and GA(4) to GA(34). Molecular and linkage analysis maps the OsGA3ox1 gene to the distal end of the short arm of chromosome 5; the OsGA3ox2 gene maps to the distal end of the short arm of chromosome 1 that corresponds to the D18 locus. The association of the OsGA3ox2 gene with the d18 locus is confirmed by sequence and complementation analysis of three d18 alleles. Complementation of the d18-AD allele with the OxGA3ox2 gene results in transgenic plants with a normal phenotype. Although both genes show transient expression, the highest level for OsGA3ox1 is from unopened flower. The highest level for OsGA3ox2 is from elongating leaves.

Amino Acid Sequence↗

PubMed1993

Gibberellin A1 is required for stem elongation in spinach.

The effects of the growth retardants 2'-isopropyl-4'-(trimethylammonium chloride)-5'-methylphenyl piperidine-1-carboxylate (AMO-1618) and calcium 3,5-dioxo-4-propionylcyclohexanecarboxylate (BX-112) on stem elongation were investigated in the rosette plant spinach (Spinacia oleracea L.) under long-day (LD) conditions. Stem growth induced by a LD treatment was prevented by both retardants. The inhibition caused by AMO-1618 was reversed by gibberellin A1 (GA1) and GA20, whereas the effects of BX-112 were reversed by GA1 only. Six GAs (GA53, GA44, GA19, GA20, GA1, and GA8) were quantified by gas chromatography-selected ion monitoring using internal standards. Plants treated with BX-112 had reduced levels of GA1 and GA8 and accumulated GA53, GA44, GA19, and GA20. The relative levels of four additional GAs (3-epi-GA1, GA29, GA60, and GA81) were compared by ion intensities only. Relative to GA81, the level of GA29 was decreased by BX-112, whereas the levels of GA60 and 3-epi-GA1 were increased. Transfer of spinach from short-day conditions to LD conditions caused an increase in all identified GAs of the early 13-hydroxylation pathway with GA20, GA1, and GA8 showing the largest increases. These findings support the position that, of the GAs belonging to the early 13-hydroxylation pathway, GA1 is the primary GA active per se for stem elongation in spinach. The increase in endogenous GA1 in plants in LD conditions is most likely the primary factor for stem elongation.

Journal Article↗

PubMed1997

Cloning gibberellin dioxygenase genes from pumpkin endosperm by heterologous expression of enzyme activities in Escherichia coli.

Gibberellin (GA) plant hormones are biosynthesized via complex pathways, the final steps of which are catalyzed by 2-oxoglutarate-dependent dioxygenases. Here, the cloning of two such enzymes, the GA 7-oxidase and the GA 20-oxidase, is reported using a novel approach, namely, by screening for GA dioxygenase activities expressed as T7 gene 10 fusion proteins in recombinant Escherichia coli. In vitro translation products of mRNA from endosperm of immature pumpkin seeds contained three GA dioxygenase activities, including 7-oxidase, 20-oxidase, and 3beta-hydroxylase. A cDNA expression library was prepared from the endosperm mRNA in lambdaMOSElox. An aliquot of the amplified library was converted to plasmids in vivo and used for transformation of E. coli BL21(DE3), which thereafter expressed recombinant fusion proteins containing 7-oxidase, 20-oxidase, and 3beta-hydroxylase activities. By screening for specific GA dioxygenase expression, clones harboring 7-oxidase and 20-oxidase cDNA were isolated. The ORF of the 7-oxidase cDNA is 945 bp long, encoding for 314 amino acid residues with a calculated Mr of 35,712 and pI of 5.7. Recombinant GA 7-oxidase oxidizes GA12-aldehyde to GA12 and GA14-aldehyde to GA14. Evidence was obtained for further metabolism of GA12 by the 7-oxidase to four products, two of which are monohydroxylated GA12. The ORF of the 20-oxidase is-apart from seven changes, resulting in four amino acid substitutions-identical to the 20-oxidase cDNA previously cloned from pumpkin cotyledon mRNA; both 20-oxidases have the same catalytic properties.

Amino Acid Sequence↗

PubMed2002

The gibberellin 20-oxidase of Gibberella fujikuroi is a multifunctional monooxygenase.

The genes for gibberellin (GA) biosynthesis are clustered in the fungus Gibberella fujikuroi. In addition to genes encoding a GA-specific geranylgeranyl diphosphate synthase and a bifunctional ent-copalyl diphosphate/ent-kaurene synthase, the cluster contains four cytochrome P450 monooxygenase genes (P450-1, -2, -3, -4). Recently it was shown that P450-4 and P450-1 encode multifunctional enzymes catalyzing the three oxidation steps from ent-kaurene to ent-kaurenoic acid and the four oxidation steps from ent-kaurenoic acid to GA14, respectively. Here we describe the functional analysis of the P450-2 gene by gene disruption and by expressing the gene in a mutant that lacks the entire GA biosynthesis gene cluster. Mutants in which P450-2 is inactivated by the insertion of a large piece of DNA accumulated GA14 and lacked biosynthetically more advanced metabolites, indicating that the gene encodes a 20-oxidase. This was confirmed by incubating lines containing P450-2 in the absence of the other GA biosynthesis genes with isotopically labeled substrates. The P450-2 gene product oxidized the 3beta-hydroxylated intermediate, GA14, and its non-hydroxylated analogue GA12 to GA4 and GA9, respectively. Expression of P450-2 is repressed by high amounts of nitrogen in the culture medium but is not affected by the presence of biosynthetically advanced GAs, i.e. there is no evidence for feedback regulation. The fact that the GA 20-oxidase is a cytochrome P450 monooxygenase in G. fujikuroi and not a 2-oxoglutarate-dependent dioxygenase as in plants, together with the significant differences in regulation of gene expression, are further evidence for independent evolution of the GA biosynthetic pathways in plants and fungi.

Blotting, Northern↗

PubMed2004

Cloning of a cDNA encoding an ETR2-like protein (Os-ERL1) from deep water rice (Oryza sativa L.) and increase in its mRNA level by submergence, ethylene, and gibberellin treatments.

A cDNA from deep water rice treated with ethylene, encoding an ethylene receptor homologous to Arabidopsis thaliana ETR2 and EIN4, was isolated using differential display and RACE techniques. The cDNA (2880 bp), corresponding to the Os-ERL1 gene (Oryza sativa ETHYLENE RESPONSE 2 like 1; GenBank accession number AB107219), contained an open reading frame of 2289 bp coding for 763 amino acids. The protein Os-ERL1 has 50% and 52% similarity to Arabidopsis ETR2 and EIN4, respectively. The Os-ERL1 gene was up-regulated by flooding, and by treatment with ethylene and gibberellin. These results suggest that deep water rice responds to flooding by increasing the number of its ethylene receptors.

Amino Acid Sequence↗

PubMed2005

Expression of two genes encoding gibberellin 2- and 3-oxidases in developing seeds of Phaseolus coccineus.

We have isolated PcGA3ox1, a cDNA clone from developing runner bean (Phaseolus coccineus) seeds that shows significant amino acid homology with the gibberellin (GA) 3-oxidases. A recombinant fusion protein of PcGA3ox1 converted GA20 and GA9 to GA1 and GA4, respectively. In situ hybridization results showed that transcripts of this gene accumulate specifically within the suspensor of globular-stage embryos. PcGA3ox1 mRNA begins to accumulate in the epidermal cells of the embryo proper and is also detectable in the endosperm during the transition from globular- to heart-stage embryos. PcGA3ox1 transcripts were localized exclusively in the cotyledons from the early cotyledonary stage up to the cotyledonary stage. Transcripts of the previously cloned GA 2-oxidase (PcGA2ox1) from developing seeds of runner bean were found primarily within the suspensor neck region from the late globular stage up to the heart stage. PcGA2ox1 mRNA was detectable in the whole suspensor from the early cotyledonary stage, and was found in the inner layer of integuments at the cotyledonary stage. Soluble enzyme preparations made from suspensors and embryos at two stages of embryogenesis (the heart and cotyledonary stages) were incubated with [14C]GA20 and [14C]GA1. Only young suspensor preparations converted GA20 to GA1 and GA5. Both suspensor preparations converted GA1 to GA8. Both embryo preparations converted GA20 to GA1, but were unable to convert GA1 to GA8.

Cell-Free System↗

PubMedDate not supplied

Transport and metabolism of gibberellins in relation to flower bud differentiation in Norway spruce (Picea abies).

A mixture of tritiated and deuterated gibberellin A(4) (GA(4)) was injected into the xylem of Norway spruce (Picea abies (L.) Karst) propagules, below an elongating shoot, or applied directly on the needles of an elongating shoot. The distribution of [(2)H(2)]GA(4) and [(3)H]GA(4) in the needles, stems and buds was determined after 4, 12 and 24 h. After 4 h, most of the xylem-injected GA(4) was found in the needles, whereas after 24 h, most of the GA(4) was found in the stem, with a small portion in the lateral buds. Of the GA(4) applied to the needles, 51% of the radioactivity recovered after 24 h was found in the stem and 2% in the lateral buds. Mixtures of tritiated and deuterated GA(4) and GA(9) were injected into elongating shoots of one abundant-flowering family and one limited-flowering family, grown either under conditions inductive for flowering (hot and dry, HD) or under noninductive conditions for flowering (cool and wet, CW). Shoots of both CW- and HD-treated propagules converted [(2)H(2)]GA(9) to [(2)H(2)]GA(51), [(2)H(2)]GA(4), [(2)H(2)]GA(34) and [(2)H(2)]GA(1), whereas [(2)H(2)]GA(4) was converted to [(2)H(2)]GA(34), [(2)H(2)]GA(1) and [(2)H(2)]GA(8). In shoots of both CW-treated clones, the main metabolite of [(3)H]GA(9) was in the GA(51) region. The HD-treated propagules converted more [(3)H]GA(9) to putative GA(4) than the CW-treated propagules. The main metabolite of [(3)H]GA(4) was in the GA(34) region. Radioactive metabolites were also found in the GA(1) and GA(8) regions.

Journal Article↗

PubMedDate not supplied

Effects of gibberellin A(4/7), root pruning and cytokinins on seed and pollen cone production in black spruce (Picea mariana).

Stem injections of 8-9-year-old black spruce (Picea mariana (Mill.) B.S.P.) trees with gibberellin A(4/7) (GA(4/7)) alone and in combination with root pruning increased both seed and pollen cone production in both 1991 and 1992. Combining GA(4/7) and root pruning produced a larger increase in reproductive bud production than either treatment alone, but the complementary effects were less during the warm dry summer in 1991 than during the wet summer in 1992. Cytokinin applications reduced the stimulatory effects of GA(4/7) and root pruning, and the degree of reduction varied with the amount and timing of application. Reduced reproductive bud production was attributed to cytokinin countering the effects of root pruning and natural drought on the GA(4/7) response.

Journal Article↗

PubMedDate not supplied

Influences of crown size and maturation on flower production and sex expression in Picea glauca treated with gibberellin A(4/7).

We evaluated the effects of exogenous gibberellin A(4/7) (GA(4/7)) on the production of seed and pollen cones in four stock types of Picea glauca (Moench) Voss. From 1987 to 1991, a combined treatment that included GA(4/7), root pruning and heat stress was applied to 5- to 10-year-old container-grown grafts, representing over 90 clones and originating from 17- to 27-year-old ortets. Hormonal treatments were applied to pruned field-grown grafts in 1991 and 1992, and to unpruned field-grown grafts from the same set of clones in 1990, 1991 and 1992. In 1992, 26-year-old mature trees in a progeny test were treated with GA(4/7). The GA(4/7) treatment was effective in promoting seed-cone production in all four stock types, whereas it promoted pollen-cone production only in unpruned field-grown grafts and mature trees. The older and taller a tree, the less the response to the GA(4/7) treatment was influenced by the climatic conditions prevailing during the differentiation phase.

Journal Article↗

PubMed1997

Control of longitudinal and cambial growth by gibberellins and indole-3-acetic acid in current-year shoots of Pinus sylvestris.

We investigated the involvement of gibberellins (GAs) and indole-3-acetic acid (IAA) in the control of longitudinal and cambial growth in current-year shoots of Pinus sylvestris L. Elongating terminal shoots, located at the apex of previous-year (1-year-old) branches in the uppermost whorl on the main stem, were variously decapitated (apical 5 to 10 mm removed), defoliated (all developing needle fascicles removed) and treated with endogenous GA(4/7) or IAA, or both. Shoot length and the radial widths of xylem and phloem were measured, and the concentrations of GA(1), GA(3), GA(4), GA(9) and IAA in the stem were determined by combined gas chromatography-mass spectrometry with deuterated GAs and [(13)C(6)]-IAA as internal standards. Decapitation decreased the production of xylem and phloem and the IAA concentration, but did not alter either longitudinal growth or the concentrations of GAs. Defoliation markedly inhibited shoot elongation, as well as cambial growth, and reduced the concentrations of GA(1), GA(3), GA(4), GA(9) and IAA. Application of GA(4/7) to defoliated shoots promoted longitudinal growth and phloem production, without affecting xylem production or IAA concentration. Application of GA(4/7) and IAA together to decapitated + defoliated shoots increased shoot elongation, xylem and phloem production and IAA concentration, whereas applying either substance alone had a smaller effect or none at all. We conclude that, for elongating current-year shoots of Pinus sylvestris, (1) both the shoot apex and the developing needle fascicles are major sources of the IAA present in the stem, whereas stem GAs originate primarily in the needle fascicles, (2) GAs and IAA are required for both shoot elongation and cambial growth, and (3) GAs act directly in the control of shoot growth, rather than indirectly through affecting the IAA concentration.

Journal Article↗

PubMed1992

Seed effects on gibberellin metabolism in pea pericarp.

Pea fruit (Pisum sativum L.) is a model system for studying the effect of seeds on fruit growth in order to understand coordination of organ development. The metabolism of (14)C-labeled gibberellin A(12) (GA(12)) by pea pericarp was followed using a method that allows access to the seeds while maintaining pericarp growth in situ. Identification and quantitation of GAs in pea pericarp was accomplished by combined gas chromatography-mass spectrometry following extensive purification of the putative GAs. Here we report for the first time that the metabolism of [(14)C]GA(12) to [(14)C]GA(19) and [(14)C]GA(20) occurs in pericarp of seeded pea fruit. Removal of seeds from the pericarp inhibited the conversion of radiolabeled GA(19) to GA(20) and caused the accumulation of radiolabeled and endogenous GA(19). Deseeded pericarp contained no detectable GA(20), GA(1), or GA(8), whereas pericarp with seeds contained endogenous and radiolabeled GA(20) and endogenous GA(1). These data strongly suggest that seeds are required for normal GA biosynthesis in the pericarp, specifically the conversion of GA(19) to GA(20).

Journal Article↗

PubMed1992

Regulation of sucrose phosphate synthase by gibberellins in soybean and spinach plants.

Exogenous applications of gibberellins (GAs) increased the extractable activity of leaf sucrose phosphate synthase (SPS) in soybean (Glycine max [L.]) and spinach (Spinacia oleracea [L.]). The response to GA applications was detectable within 2 h postapplication and was still observed 6 h, 24 h, and 7 d after treatment. When paclobutrazol, a GA biosynthesis inhibitor, was applied to intact soybean and spinach plants, decreased extractable SPS activity resulted within 24 h following the treatment. Different methods of GA application (spray, injection, capillary wick, and excised leaf systems) produced similar effects on SPS activity of soybean leaves. Protein synthesis in soybean leaves appeared to be necessary for GA-promoted SPS activity because gibberellic acid only partially reversed the inhibitory effect of pretreatment with cycloheximide. Levels of SPS protein from crude extracts of spinach plants were measured by a dot blot technique using monoclonal antibodies against SPS. Application of gibberellic acid to spinach leaves increased levels of SPS protein 2 h, 24 h, and 7 d after treatment. The results suggest that, in both soybean and spinach, GA is one of the endogenous hormonal factors that regulate the steady-state level of SPS protein and, hence, its activity.

Journal Article↗

PubMed1992

Gibberellin concentration and transport in genetic lines of pea : effects of grafting.

Effects of the Na and Le loci on gibberellin (GA) content and transport in pea (Pisum sativum L.) shoots were studied. GA(1), GA(8), GA(17), GA(19), GA(20), GA(29), GA(44), GA(8) catabolite, and GA(29) catabolite were identified by full-scan gas chromatography-mass spectrometry in extracts of expanding and fully expanded tissues of line C79-338 (Na Le). Quantification of GAs by gas chromatography-single-ion monitoring using deuterated internal standards in lines differing at the Na and Le alleles showed that na reduced the contents of GA(19), GA(20), and GA(29) on average to <3% and of GA(1) and GA(8) to <30% of those in corresponding Na lines. In expanding tissues from Na le lines, GA(1) and GA(8) concentrations were reduced to approximately 10 and 2%, respectively, and GA(29) content increased 2- to 3-fold compared with those in Na Le plants. There was a close correlation between stem length and the concentrations of GA(1) or GA(8) in shoot apices in all six genotypes investigated. In na/Na grafts, internode length and GA(1) concentration of nana scions were normalized, the GA(20) content increased slightly, but GA(19) levels were unaffected. Movement of labeled GAs applied to leaves on Na rootstocks indicated that GA(19) was transported poorly to apices of na scions compared with GA(20) and GA(1). Our evidence suggests that GA(20) is the major transported GA in peas.

Journal Article↗