Gibberellins and parthenocarpic ability in developing ovaries of seedless mandarins

Satsuma (Citrus unshiu [Mak] Marc.) and Clementine (Citrus reticulata [Hort.] Ex. Tanaka, cv Oroval) are two species of seedless mandarins differing in their tendency to develop parthenocarpic fruits. Satsuma is a male-sterile cultivar that shows a high degree of natural parthenocarpy and a high fruit set. Seedless Clementine varieties are self-incompatible, and in the absence of cross-pollination show a very low ability to set fruit. The gibberellins (GAs) GA53, putative 17-OH-GA₅₃, GA₄₄, GA₁₇, GA₁₉, GA₂₀, GA₂₉, GA₁, 3-epi-GA₁, GA₈, GA₂₄, GA₉, and GA₄ have been identified from developing fruits of both species by full-scan combined gas chromatography-mass spectrometry. Using selected ion monitoring with [²H₂]- and [¹³C]-labeled internal standards, the levels of GA₅₃, GA₄₄, GA₁₉, GA₂₀, GA₁, GA₈, GA₄, and GA₉ were determined in developing ovaries at anthesis and 7 days before and after anthesis, from both species. Except for GA8, levels of the 13-hydroxy-GAs were higher in Satsuma than in Clementine, and these differences were more prominent for developing young fruits. At petal fall, Satsuma had, on a nanograms per gram dry weight basis, higher levels of GA₅₃ (10.4x), GA₄₄ (13.9x), GA₁₉ (3.0x), GA₂₀ (11.2x), and GA₁ (2.0x). By contrast, levels of GA₈ were always higher in Clementine, whereas levels of GA₄ did not differ greatly. Levels of GA₉ were very low in both species. At petal fall, fruitlets of Satsuma and Clementine contained 65 and 13 picograms of GA₁, respectively. At this time, the application of 25 micrograms of paclobutrazol to fruits increased fruit abscission in both varieties. This effect was reversed by the simultaneous applications of 1 microgram of GA₃. GA₃ alone improved the set in Clementine (13x), but had little influence on Satsuma. Thus, seedless fruits of the self-incompatible Clementine mandarin may not have adequate GA levels for fruit set. Collectively, these results suggest that endogenous GA content in developing ovaries is the limiting factor controlling the parthenocarpic development of the fruits.     

Strong synergistic effects of gibberellins with the synthetic cytokinin N-(2-chloro-4-pyridyl)-N-phenylurea on parthenocarpic fruit set and some other fruit characteristics of apple

The induction of parthenocarpic fruit set was investigated using the apple cvs. Golden Delicious and Jonagold. The gibberellins GA₃, GA₄, GA₅ and GA₇ and the synthetic phenylurea-type cytokinin CPPU (N-(2-chloro-4-pyridyl)-N-phenylurea), were applied alone and in combination to unpollinated flowers at the end of petal fall. Gibberellins induced only a marginal final set of parthenocarpic fruits. CPPU sprays were more effective, particularly in the first year. When applied in combination, CPPU and gibberellins had a positive synergistic effect on parthenocarpic fruit set and fruit size, but a negative effect on flower induction the next year. After CPPU + GA sprays, percent fruit set was similar, or greater, compared to natural pollinated trees. The parthenocarpic fruits induced by CPPU + GA had an increased length to diameter ratio. CPPU stimulated, and GA₄ and GA₇ reduced, the russeting of the parthenocarpic fruits. The internal quality of the fruits was hardly affected, but Ca-deficiency symptoms occurred more frequently in parthenocarpic fruits.     

Transport and metabolism of exogenously applied gibberellins to Malus domestica Borkh. cv. Jonagold

The radio-labeled gibberellins GA₁, GA₃,GA₄, and GA₇ were applied to intact developing applefruits (Malus domestica Borkh. cv. Jonagold) during theperiod when GAs are suggested to inhibit flower bud induction for the followingyear. Radioactivity from these compounds was found to be transported intoadjacent tissues as there are pedicels and bourses (4%). Application topedicels, after removal of the fruits, enhanced the transport into adjacentbourses up to 11%. The bud-carrying lateral bourse shoots contained onlyminor amounts of radioactivity on average 0.4% in both cases. Theseexport rates were identical, 1 or 5 days after application.After application of the corresponding deuterium-labeled GAs and analyses bymass spectrometry the specific metabolization of GA₁ toGA₁ 13-O-glucoside and of GA₃ to GA₃13-O-glucoside was demonstrated. Additional metabolites of GA₁ andGA₃ were not detected. After fruit application of GA₃ theratio of GA₃ to GA₃ 13-O-glucoside was found to be 1:2 inthe fruit. Pedicel application led to ratios of 1:4 and 1:5, respectively, inthe pedicel and in the adjacent bourse. After the application of GA₄and GA₇, neither glucosylation products nor other GA-like metabolitescould be identified.This is the first report of the metabolism of GAs to GA 13-O-glucosides indeveloping apple fruits. The possible function of the GAs as a signal in flowerbud formation for the following year is discussed.     

The Structure of Gibberellin A23 and the Biological Properties of 3,13-Dihydroxy C20-Gibberellins

Two aldehydic C₂₀-gibberellins, L-2 and L-4, were isolated from the immature fruits of yellow lupine (Lupinus luteus L.). L-2 was shown to have the structure II and named gibberellin A₂₃. L-4 was identified as gibberellin A₁₉(VI). Two new C₂₀-gibberellins, tentatively called 3,13-dihydroxy GA₁₅(IV) and 13-hydroxy GA₁₅(VIII), were derived from gibberellins, A₂₃ and A₁₉, respectively. The biological activities of four 3,13-dihydroxy C₂₀-gibberellins-GA₁₈(I), GA₂₃(II), GA₂₈(III) and 3,13-dihydroxy GA₁₅(IV), which were isolated from the fruits except for 3,13-dihydroxy GA₁₅—were compared in six gibberellin bioassays.     

Hormonal changes associated with fruit set and development in mandarins differing in their parthenocarpic ability

Satsuma [Citrus unshiu (Mak) Marc.] and Clementine [Citrus reticulata (Hort.) Ex. Tanaka, cv. Oroval] are two related species of seedless mandarins which differ in their tendency to set parthenocarpic fruits. Satsuma fruits naturally set parthenocarpically whereas Clementine mandarins show very low ability to set fruit in the absence of cross-pollination. The endogenous levels of gibberellins (GAs) and free and conjugated indole-acetic acid (IAA) and abscisic acid (ABA) throughout early stages of fruit development were investigated in seedless cultivars of both species. Analyses performed by full-scan combined gas chromatography-mass spectrometry (GC-MS) of extracts from ovaries at anthesis demonstrated the presence of GA₁₉, GA₂₀, GA₂₉, GA₁, GA₈, GA₃ and iso-GA₃ in Satsuma mandarin, whereas only GA₂₉, GA₃ and trace levels of GA₈ were detected in Clementine. At this developmental stage GA-like substances, as estimated by bioassay, reached their highest levels in Satsuma, while Clementine mandarins contained relatively lower levels. In both species the highest levels of free IAA were found at petal-fall stage at which time free ABA levels also peaked. Developing fruits of Clementine had higher amounts of both free IAA and ABA. In Satsuma, levels of conjugated IAA remained low throughout reproductive development whereas in Clementine they increased as the free form declined. In contrast, conjugated ABA was at low levels in Clementine but reached higher concentrations in Satsuma. These results suggest that in these mandarins the potential for setting parthenocarpic fruits is mainly influenced by the hormonal status of the fruit during the later stages of cell division and early stages of cell enlargement. Thus, the condition of low ability to set parthenocarpic fruits appears to be associated with lower levels of active GAs, lower capability to catabolize ABA to conjugated ABA and higher ability to conjugate IAA during this period.     

Expression of gibberellin mutations in fruits of Pisum sativum L.

The gibberellin (GA) economy of young pea (Pisum sativum L.) fruits was investigated using a range of mutants with altered GA biosynthesis or deactivation. The synthesis mutation lh-2 substantially reduced the content of both GA₄ and GA₁ in young seeds. Among the other synthesis mutations, ls-1, le-1 and le-3, the largest reduction in seed GA₁ content was only 1.7-fold (le-1), while GA₄ was not reduced in these mutants, and in fact accumulated in some experiments (compared with the wild type). Mutation sln appeared to block the step GA₂₀ to GA₂₉ in young pods and seeds, but not as strongly as in older seeds. Mutations ls-1, le-1 and le-3 markedly reduced pod GA₁ levels, but pod elongation was not affected. After feeds of [¹³C,³H]GA₂₀ to leaves, the pods contained ¹³C,³H-labelled GA₂₀, GA₁, GA₂₉ and GA₈₁, and the seeds, [¹³C,³H]GA₂₀ and [¹³C,³H]GA₂₉. These findings are discussed in relation to recent suggestions regarding the role and origin of GA₁ in pea fruits. Received: 6 June 1997 / Accepted: 15 July 1997     

C]GA(12)-Aldehyde, [C]GA(12), and [H]- and [C]GA(53) Metabolism by Elongating Pea Pericarp

Gibberellins (GAs) are either required for, or at least promote, the growth of the pea (Pisum sativum L.) fruit. Whether the pericarp of the pea fruit produces GAs in situ and/or whether GAs are transported into the pericarp from the developing seeds or maternal plant is currently unknown. The objective of this research was to investigate whether the pericarp tissue contains enzymes capable of metabolizing GAs from [¹⁴C]GA₁₂-7-aldehyde ([¹⁴C]GA₁₂ald) to biologically active GAs. The metabolism of GAs early in the biosynthetic pathway, [¹⁴C]GA₁₂ and [¹⁴C]GA₁₂ald, was investigated in pericarp tissue isolated from 4-day-old pea fruits. [¹⁴C]GA₁₂ald was metabolized primarily to [¹⁴C]GA₁₂ald-conjugate, [¹⁴C]GA₁₂, [¹⁴C]GA₅₃, and polar conjugate-like products by isolated pericarp. In contrast, [¹⁴C]GA₁₂ was converted primarily to [¹⁴C]GA₅₃ and polar conjugate-like products. Upon further investigations with intact 4-day-old fruits on the plant, [¹⁴C]GA₁₂ was found to be converted to a product which copurified with endogenous GA₂₀. Lastly, [²H]GA₂₀ and [²H]GA₁ were recovered 48 hours after application of [²H]- and [¹⁴C]GA₅₃ to pericarp tissue of intact 3-day-old pea fruits. These results demonstrate that pericarp tissue metabolizes GAs and suggests a function for pericarp GA metabolism during fruit growth.     

Influence of an inhibitor of gibberellin biosynthesis, paclobutrazol, on apple seed gibberellin content

Tissue-culture-propagated own-rooted cv. Spartan apple trees (Malus domestica Borkh.) planted in 1979 were treated in 1983 and 1985 via a soil-line trunk drench with the plant growth retardant paclobutrazol [(2RS, 3RS)-1-(4-chlorophenyl)-4.4-dimethyl-2-(1,2, 4-triazol-1-yl) pentan-3-ol]. Seeds of immature fruits from untreated and treated trees were sampled in 1989 ca 75 days after full bloom. After seeds were freeze-dried, gibberellins (GAs) were extracted, purified and fractionated via C₁₈ reversed-phase high-performance liquid chromatography (HPLC). Gibberellins A₁, A₃, A₄, A₇, A₈, A₉, A₁₅, A₁₇, A₁₉, A₂₀, A₂₄, A₃₄, A₃₅, A₄₄, A₅₁, A₅₃, A₅₄, A₆₁, A₆₂, A₆₃ and A₆₈ were identified by using C₁₈ HPLC, gas chromatography-selected ion monitoring and Kovats retention indices. Eight of the GAs identified were also quantified by using deuterated internal standards. The paclobutrazol applications caused a 55% reduction of vegetative shoot elongation in 1989, but both treated and untreated trees had developed a biennial bearing pattern by that time (heavy bloom or “on year’in 1989). Levels of early 13-hydroxylation pathway GAs, viz. GA₅₃, GA₁₉, GA₂₀, GA₁ and also GA₃, were not altered by treatment. However, GA₄, GA₇ and GA₉ were increased 13.4, 6.5 and 3.8 times, respectively, in seeds of fruit from treated compared to untreated trees.     

Enhancement of [C]Sucrose Export from Source Leaves of Vicia faba by Gibberellic Acid

The effect of gibberellic acid (GA₃) on sucrose export from source leaves was studied in broad bean (Vicia faba L.) plants trimmed of all but one source and one sink leaf. GA₃ (10 micromolar) applied to the source leaf, enhanced export of [¹⁴C]sucrose (generated by ¹⁴CO₂ fixation) to the root and to the sink leaf. Enhanced export was observed with GA treatments as short as 35 minutes. When GA₃ was applied 24 hours prior to the ¹⁴CO₂ pulse, the enhancement of sucrose transport toward the root was abolished but transport toward the upper sink leaf was unchanged. The enhanced sucrose export was not due to increased photosynthetic rate or to changes in the starch/sucrose ratio within the source leaf; rather, GA₃ increased the proportion of sucrose exported. After a 10-min exposure to [¹⁴C]GA₃, radioactivity was found only in the source leaf. Following a 2 hour exposure to [¹⁴C]GA₃, radioactivity was distributed along the entire stem and was present in both the roots and sink leaf. Extraction and partitioning of GA metabolites by thin layer chromatography indicated that there was a decline in [¹⁴C]GA₃ in the lower stem and root, but not in the upper stem. This pattern of metabolism is consistent with the disappearance of the GA₃ effect in the lower stem with time after treatment. We conclude that in the short term, GA₃ enhances assimilate export from source leaves by increasing phloem loading. In the long term (24 hours), the effect of GA₃ is outside the source leaf. GA₃ accumulates in the apical region resulting in enhanced growth and thus greater sink strength. Conversely, GA₃ is rapidly metabolized in the lower stem thus attenuating any GA effect.     

The effect of gibberellins on the storage life of plantains

Dipping plantain fruits in gibberellins (GA_4/7 or GA₃) delayed the ripening of individual fruits by approximately 50%, the two treatments being equally effective. Measurement of the preclimacteric period (PCP) by increased respiration showed that plantain fruits vacuum infiltrated with GA_4/7 (10^-5 M) gave an extension of 37% in the PCP under high humidity. No effect was observed at low humidity. The use of gibberellins on plantain storage is discussed.     

Gibberellin content of immature apple seeds from paclobutrazol-treated trees over three seasons

Seeds from heavily fruiting (on-year), mature untreated, and paclobutrazol-treated apple trees (Malus domestica Borkh. cv. Spartan) were sampled in mid-June 1987, mid-July 1987, and mid-July 1990. After seeds were freeze-dried, gibberellins (GAs) were extracted, purified, and fractionated via C₁₈ reversed-phase high-performance liquid chromatography (HPLC). Nine GAs (GA₁, GA₃, GA₄, GA₇, GA₈, GA₉, GA₁₉, GA₂₀, and GA₅₃) were quantified by the use of deuterated GA internal standards. Paclobutrazol trunk drench treatments reduced vegetative shoot elongation in the seasons that seeds were sampled by 55% or more. Between June 17, 1987 and July 15, 1987, the dry weight of seeds from both untreated and treated trees increased about 2.5 times and there were reductions, on a per seed basis, of GA₄ in seeds from both untreated and treated trees, of GA₇ in seeds from treated trees, and of GA₉ in seeds from untreated trees. However, GA₉ increased in seeds from treated trees. Changes in levels of some of the early-13-hydroxylation pathway GAs (GA₁₅ GA₃, GA₈, GA₁₉, GA₂₀, and GA₅₃) also occurred during the month. For mid-July harvested seeds, the pattern, with some exceptions, was that 2 years after paclobutrazol treatment (1987), levels of early-13-hydroxylation pathway GAs in seeds from treated trees were lower compared to controls but after 5 years (1990) their levels tended to increase. For the non-13-hydroxylated GAs (GA₄, GA₇, and GA₉), 2 years after paclobutrazol treatment, GA₄ levels were equal in seeds from untreated and treated trees, GA₇ decreased in seeds from treated trees compared with controls, but GA₉ levels increased. Levels of these three GAs were higher in seeds from treated trees 5 years after treatment (1990) but levels of GA₄, GA₇, and GA₉ dramatically increased in seeds from treated trees 4 years after treatment (1989), as we previously reported.     

Gibberellins inCitrus sinensis: A comparison between seeded and seedless varieties

The gibberellin (GA) content of the reproductive organs ofCitrus sinensis (L.) Osb., cv. Bianca Comuna and the seedless variety, Salustiana, were examined by combined gas chromatography-mass spectrometry (GC/MS) at different stages of development. Gibberellins A₁, A₂₀, and A₂₉ were identified in the reproductive buds of both cultivars 21 days prior to anthesis and in fruits 35 days after anthesis by comparison of their mass spectra and Kovats retention indices with those of standards. In addition, three uncharacterized isomers of GA₁ were detected, one in buds and two in fruits. The presence of GA₄ in both tissues, and of GA₈ in the reproductive buds, was indicated by the occurrence of characteristic ions at the expected retention times, although their spectra were too weak for full identification. Vegetative shoots of cv. Salustiana contained gibberellins A₁, A₁₉, A₂₀, and A₂₉, and the unidentified isomer of GA₁ present in reproductive buds. The presence of trace amounts of gibberellins A₈ and A₁₇ was also indicated. Although the two varieties did not differ qualitatively in the GAs present during flower and fruit development, the seedless variety contained slightly greater amounts. The concentrations of gibberellins A₁, A₄, and A₂₀ were determined by gas chromatography-selected ion monitoring (GC/SIM) throughout ovary development and early fruit growth. In both varieties, the maximum GA₁ concentration occurred at anthesis. Highest concentrations of gibberellins A₂₀ and A₄ were found in fruit 35 days after anthesis, although the GA₁ concentration at this stage remained low.     

Endogenous gibberellins in clover broomrape,a parasitic plant,and its host,clover: Dependency of the parasite on the host for gibberellin production

Endogenous gibberellins were analyzed from a parasitic plant, clover broomrape (Orobanche minor Smith), and its host, clover (Trifolium repens L.). Members of both the early-13- and the early-non-hydroxylation pathways were identified from both the parasite and the host (GA₁₂, GA₂₄, GA₉ GA₄, GA₄₄, GA₁₉, GA₂₀, and GA₁ from clover broomrape; GA₉, GA₄, GA₄₄, GA₁₉, GA₂₀, and GA₁ from clover). Quantitative analyses showed that GA₄₄ was present at high levels in both host and parasite. The similarity in the gibberellins suggests the possibility that the major gibberellins in clover broomrape are transported from clover. However gibberellins such as GA₅₈, GA₃₈, and notably GA₄₇ which was identified from a plant for the first time were detected only from clover broomrape, suggesting that the parasite may have the ability to produce at least those gibberellins     

Endogenous gibberellins and inhibitors in caryopses of rye

Gibberellins A₈, A₁₆, A₂₄, and abscisic acid were identified by GC-MS of derivatized extracts from immature fruits of Secale cereale. Mature caryopses contained ABA and trans-ABA in a ratio 1:1 as well as 4′-dihydrophaseic acid. During milk ripeness a neutral GA conjugate was detected. Free GA, afforded by enzymatic hydrolysis of the conjugate, was chromatographically identified as GA₁₆     

Identification of Ten Gibberellins from Sporophytes of the Tree fern, Cyathea australis

Ten gibberellins (GAs) have been identified by Kovats retention indices and full mass spectra from GC-MS analysis of purified extracts of sporophytes of the tree-fern, Cyathea australis. These include the known GA₁, GA₄, GA₉, GA₁₅, GA₂₄, GA₃₅, and GA₅₈ and three new GAs, 12β-hydroxyGA₉ (GA₆₉), 12α-hydroxyGA₉ (GA₇₀) and 12β-hydroxyGA₄ (GA₇₁). The structure of GA₇₁ was established by the preparation and characterization of its methyl ester (as a metabolite of GA₄ methyl ester in a culture of prothallia of Lygodium japonicum).     

Endogenous gibberellins in the shoots of normal- and bush-typeCucumis sativus L.

Endogenous gibberellins (GAs) in the shoots of normal- (cv. Yomaki, YO) and bush-type (cv. Spacemaster, SP) cultivars of cucumber (Cucumis sativus L.) grown under natural conditions were analyzed. From both YO and SP grown for 40 days, after sowing, a series of C-13-H GAs including GA₄, GA₉, GA₁₅, GA₂₄, GA₂₅, GA₃₄, and GA₅₁ were identified by gas chromatography-mass spectrometry (GC-MS; full scan). In addition to the above GAs, GA₁₂ and GA₇₀ were similarly identified from both YO and SP grown for 61 days after sowing. The endogenous levels of GA₄ and GA₉, which are highly active in promoting cucumber hypocotyl elongation, were quantified by GC-selected ion monitoring (GC-SIM) using [²H₂]GA₄ and [²H₄]GA₉ as internal standards. No remarkable difference in terms of endogenous levels of GA_4/9 was observed between YO and SP in both growth stages (40 and 61 days after sowing).     

Gibberellins in Embryo-Suspensor of Phaseolus coccineus Seeds at the Heart Stage of Embryo Development

Gibberellins (GAs) in suspensors and embryos of Phaseolus coccineus seeds at the heart stage of embryo development were analyzed by combined gas chromatography-mass spectrometry (GC-MS). From the suspensor four C₁₉-GAs, GA₁, GA₄, GA₅, GA₆, and one C₂₀ GA, GA₄₄, were identified. From the embryo, five C₁₉-GAs GA₁, GA₄, GA₅, GA₆, GA₆₀ and two C₂₀ GAs, GA₁₉ and GA₄₄ were identified. The data, in relation to previous results, suggest a dependence of the embryo on the suspensor during early stages of development.     

Identification of Endogenous Gibberellins in Dormant Bulbils of Chinese Yam, Dioscorea opposita

It is known that dormancy of the genus Dioscorea is induced by application of gibberellin (GA) A₃. To understand the role of GAs in dormancy induction, endogenous GAs have been identified by Kovats retention indices and full mass spectra from capillary gas chromatography-mass spectrometry analysis of purified extract from dormant bulbils of Dioscorea opposita Thunb. These include GA₄, GA₉, GA₁₂, GA₁₉, GA₂₀, GA₂₄, GA₃₆, and GA₅₃; their presence suggests the occurrence of two biosynthetic pathways in D. opposita bulbils, the early 13-hydroxylation pathway and the non-13-hydroxylation pathway.     

Qualitative and Quantitative Analysis of Endogenous Gibberellins in Onion Plants and Their Effects on Bulb Development

Evidence has been reported that bulb development in onion plants (Allium cepa L.) is controlled by endogenous bulbing and anti-bulbing hormones, and that gibberellin (GA) is a candidate for anti-bulbing hormone (ABH). In this study, we identified a series of C-13-H GAs (GA₁₂, GA₁₅, GA₂₄, GA₉, GA₄, GA₃₄, and 3-epi-GA₄) and a series of C-13-OH GAs (GA₄₄, GA₂₀, GA₁ and GA₈) from the leaf sheaths including the lower part of leaf blades of onion plants (cv. Senshu-Chuko). These results suggested that two independent GA biosynthetic pathways, the early-non-hydroxylation pathway to GA₄ (active GA) and early-13-hydroxylation pathway to GA₁ (active GA), exist in onion plants. It was also suggested that GA₄ and GA₁ have almost the same ability to inhibit bulb development in onion plants induced by treatment with an inhibitor of GA biosynthesis, uniconazole-P. The endogenous levels of GA₁ and GA₄, and their direct precursors, GA₂₀ and GA₉, in leaf blades, leaf sheaths, and roots of 4-week-old bulbing and non-bulbing onion plants were measured by gas chromatography/selected ion monitoring with the corresponding [²H]labeled GAs as internal standards. In most cases, the GA levels in long-day (LD)-grown bulbing onion plants were higher than those of short-day (SD)-grown non-bulbing onion plants, but the GA₁ level in leaf blades of SD-grown onion plants was rather higher than that of LD-grown onion plants. Relationship between the endogenous GAs and bulb development in onion plants is discussed.     

Quantification of GA1, GA3, GA4, GA7, GA9, and GA20 in vegetative and male cone buds from juvenile and mature trees of Pinus radiata

The gibberellins GA₁, GA₃, GA₄, GA₇, GA₉ and GA₂₀ were quantified in vegetative and pollen cone buds of juvenile and mature trees of Pinus radiata by combined gas chromatography-mass spectrometry and selected ion monitoring (GC-MS-SIM) using deuterated GAs as internal standards. Higher levels of GA₇ and GA₉ and lower levels of GA₄ were detected in juvenile vegetative buds compared to mature buds, and there were no differences in relation to age for GA₁, GA₃ and GA₂₀. Conversely, when differences between vegetative and pollen cone buds from a mature tree were studied, the highest levels of GA₁ and GA₄ were found in pollen cone buds, similar levels of GA₃, GA₇ and GA₉ were observed in both, and ten fold lower levels of GA₂₀ were found in pollen cone buds as compared with vegetative buds. These results indicate a difference in GA metabolism in relation to both the tree age as well as the physiological status of buds: vegetative or reproductive in this conifer.