Exogenous and endogenous growth regulators on apogamy in Dryopteris affinis (Lowe) Fraser-Jenkins sp. affinis

This work showed for the first time the relationship between the effect of exogenous auxins and gibberellins on apogamy in Dryopteris affinis (Lowe) Fraser-Jenkins sp. affinis and its endogenous contents during early apogamic events. The addition of NAA (0.53 and 5.37 μM) or GA₃ 2.8 μM to an MS solid medium significantly increased apogamous sporophyte formation. BA induced brown callus that regenerated sporophytes in a hormone-free medium. The endogenous contents of GA₁, GA₃, GA₄, GA₇, GA₉ and IAA were determined by GC–MS in gametophytes cultured on MS solid medium, before and during early stages of apogamous embryo development. The accumulation of both GA₉ and IAA before embryo development was evident as high levels of GA₄ in the earliest analysed stage of embryo development and high levels of GA₃ in elongating shoots were found. The role of gibberellins on apogamy was also supported by data showing a decrease in the percentage of gametophytes developing embryos because of the addition of flurprimidol to the culture medium.     

Partial characterization of an antheridiogen of Anemia mexicana: Comparison with the antheridiogen of A. phyllitidis

An antheridiogen of Anemia mexicana Klotzsch has been partially characterized by combined gas chromatography-mass spectrometry and gas chromatography-Fourier transform/infra-red spectrometry. It is a C₁₉-gibberellin(GA)-like compound with one carboxyl group, an exocyclic methylene group and a lactone ring. It also has one hydroxyl-group and one double-bond equivalent which has not been determined. On the basis of its mass spectrum, it is not identical to previously identified monohydroxy GAs with one ring double bond such as GA₅, GA₇, GA₃₁ and GA₆₂. By direct comparison of mass spectra, the antheridiogen of A. mexicana was also determined to be different from the antheridiogens of Anemia phyllitidis (L.) Swartz, Anemia hirsuta (L.) Swartz and Lygodium japonicum (Thunb.) Sw.Abbreviations GA(s) gibberellin(s) - GA_a gibberellin A_n - GC-FT/IR combined gas chromatography-Fourier transform/infra-red spectrometry - GC-MS combined gas chromatography-mass spectrometry - IR intra-red spectrometry - KRI Kovats Retention Index - m/z mass/charge - TLC thin-layer chromatography - TMSi trimethylsilyl     

Gibberellin structure-activity effects on flower initiation in mature trees and on shoot growth in mature and juvenile Prunus avium

When applied to spurs of mature Prunus avium before floral initiation, gibberellins GA₁, GA₄ and GA₃ inhibited floral initiation by 9–17%, GA₇ by 43%, GA₃ by 65–71% and 2,2-dimethyl GA₄ by 78%. GA₉ and GA₂₀ were inactive. Thus activity only of the GAs with a C-3 hydroxyl was increased markedly by a double bond in the C-1,2 or C-2,3 position, and activity increased with increasing hydroxylation. None of the GAs affected the total number of buds (vegetative and floral) surviving in the spur. Measured by the threshold dose required for activity, seedling shoot growth responses to GA₃, GA₇, GA₁ or GA₄ resembled those of floral initiation, but di-methylation of GA₄ at C-2 had no effect, and GA₉ was as active as GA₇. Mature shoots, including those on rooted cuttings, were less responsive to GA treatment than were juvenile shoots, with terminal shoots on mature trees more responsive than spur shoots. Spur shoot growth on mature trees responded to GA₃ and to a lesser extent GA₇, but not to GA₁ or GA₄. However, all these GAs promoted the growth of terminal shoots on mature trees to similar extents, whereas 2,2-dimethyl GA₄ was less active than GA₄ The differences between juvenile and mature shoot growth in sensitivity to a C-1,2 or C-2,3 double bond, and between mature shoot growth and floral initiation in GA-structure requirements, indicate that phase change alters the GA complement and/or GA receptor/transduction mechanisms of P. avium. The difference in sensitivity to 2,2-dimethyl GA₄ indicates that floral initiation and growth have different requirements for GA transport and/or action.     

Studies on morphology and metabolism of prothalli during GA3-induced formation of antheridia in Anemia phyllitidis

In Schizaeaceae ferns, including Anemia phyllitidis, formation of antheridia is known to be induced by exogenously applied gibberellic acid. Also present studies show that GA₃ (10⁻⁵ mol·dm⁻³) modifies the development of gametophytes of Anemia phyllitidis. Simultaneously with formation of antheridia, they exhibit lower number of cells but only slightly lowered profile areas and lengths of prothalli. Growth in size of individual cells compensates for lowered division frequency. Cytophotometric measurements reveal no essential changes in the DNA content in vegetative cells of the control and GA₃-stimulated gametophytes. It remains at haploid level and therefore it is assumed that cell cycle is blocked at G1 phase. Application of GA₃ increases the total amount of proteins. CZE (Capillary Zone Electrophoresis) separation of peptides extracted from control and GA₃-treated prothalli indicates the differences in the ratio of their particular forms. In GA₃-treated gametophytes the activities of acid and basic phosphatases, contents of carbohydrates (glucose, starch), chlorophyll, the number of chloroplasts and dry mass of prothalli are increased. GA₃-intensified metabolism, evidenced in gametophytes of A. phyllitidis, may be interpreted as a stimulatory mechanism which influences metabolic pathways involved in forming, developing and maturing of male sex organs.     

Growth and gender in the gametophyte of Blechnum spicant L

The growth and gender in the gametophyte of Blechnum spicant L. were strongly affected by its origin, spore or mature homogenized gametophytes, and also by the addition of plant growth regulators to the culture medium. Spore-derived gametophytes cultured in Murashige and Skoog liquid medium were females and heart-shaped, whereas those derived from mature homogenized gametophytes were shorter and male or asexual (1:3) because of the release of antheridiogen to the culture medium. In the latter, maleness was especially increased by the addition of BA. This cytokinin is a strong inductor of maleness in homogenized cultures; however, even though BA influenced sexual organ formation in spore-derived gametophytes, it does not change the␣female sexual pattern that these gametophytes have. Separate male and female populations of gametophytes were obtained in this work.     

Implication of Ethylene in the Release of Secondary Dormancy in Amaranthus caudatus L. Seeds by Gibberellins or Cytokinin

Ethephon (Eth), gibberellin A₃, A_{4 + 7} (GA₃, GA_{4 + 7}), and 6-benzyladenine (BA) removed secondary dormancy of Amaranthus caudatus seeds. The GAs and BA potentiated the effect of ethephon or 1-aminocyclopropane-1-carboxylic acid (ACC), an ethylene biosynthesis precursor, in terms of the rate or final percent of germination. Aminoethoxyvinylglycine (AVG), an ACC synthase activity inhibitor, was observed to simultaneously inhibit the release from dormancy effected by GA₃ or BA as well as the ethylene production stimulated by these regulators. Breaking of secondary dormancy by GA₃, GA_{4 + 7} or BA was prevented by 2,5-norbornadiene (NBD), an inhibitor of ethylene binding. Ethylene completely or markedly reversed the inhibitory effect of NBD. We thus conclude that the removal of secondary dormancy in Amaranthus caudatus seeds by gibberellin or benzyladenine involves ethylene biosynthesis and action.     

Free Radicals Developed in the Amino-Garbonyl Reaction of Sugars with Amino Acids

GA_l5, GA₃, GA₅, GA₁₉, GA₂₀ and GA₂₃ were identified by GC-MS in the acidic ethyl acetate-soluble fraction from the seeds of sweet potato (Ipomoea batatas Lam.). GA₁₉ and GA₂₃ were major GAs in the mature seeds, their contents being about 200 and 160 μg/kg fresh weight, respectively, while those of GA₁₉ and GA₂₃ in immature seeds were below 100 μg/kg fr. wt. The occurrence of glycosyl conjugates of GA₃, GA₅, GA₈, GA₁₇, GA₁₉, GA₂₀, GA₂₃ and GA₄₄ in the butanol fraction from mature seeds was shown by GC/MS analysis after enzymatic hydrolysis.

Besides the endogenous GAs in sweet potato, those in immature seeds of several other Convolvulaceae plants were investigated. The species of endogenous GAs were discussed in terms of chemotaxonomy.     

Quantification of GA1, GA3, GA4, GA7, GA8, GA9, GA19 and GA20; and GA20 metabolism in dormant and non-dormant beechnuts

The endogenous levels of GA₁, GA₃, GA₄, GA₇, GA₈, GA₉, GA₁₉ and GA₂₀ were determined in beech seeds (Fagus sylvatica L.) treated with different dormancy breaking treatments. Gibberellins were analysed separately in cotyledons and embryo axes. After purification of the extracts, GAs were quantified by GC-MS-selected ion monitoring (GC-MS-SIM) with deuterated GAs as internal standards. The results showed that GAs corresponding to the 13-OH pathway seemed to be involved in dormancy breaking. Strong differences in GA₁, GA₃, GA₈, GA₁₉ and GA₂₀ levels between embryo axes and cotyledons of dormant and non-dormant beechnuts were detected with less pronounced differences for GA₄, GA₇ and GA₉ levels. Both the quantitative differences between dormant and non-dormant seeds in the analysed GAs corresponding to the 13-OH pathway, and the capacity of non-dormant seeds to carry out metabolic conversions when labelled GA₂₀ was injected into the seeds, reveal a dynamic role of GAs in dormancy release.     

Accumulation of C19-gibberellins in the gibberellin-insensitive dwarf mutantgai ofArabidopsis thaliana (L.) Heynh

The endogenous gibberellins (GAs) from shoots of the GA-insensitive mutant,gai, ofArabidopsis thaliana were analyzed and compared with the GAs from the Landsberg erecta (Ler) line. Twenty GAs were identified in Ler plants by full-scan gas chromatography-mass spectrometry (GC-MS) and Kovats retention indices (KRI's). These GAs are members of the early-13-hydroxylation pathway (GA₅₃, GA₄₄, GA₁₉, GA₁₇, GA₂₀, GA₁, GA₂₉, and GA₈), the non-3,13-hydroxylation pathway (GA₁₂, GA₁₅, GA₂₄, GA₂₅, GA₉, and GA₅₁), and the early-3-hydroxylation pathway (GA₃₇, GA₂₇, GA₃₆, GA₁₃, GA₄, and GA₃₄). The same GAs, except GA₅₃, GA₄₄, GA₃₇, and GA₂₉ were detected in thegai mutant by the same methods. In addition, extracts fromgai plants contained GA₄₁ and GA₇₁. Both lines also contained several unknown GAs. In Ler plants these were mainly hydroxy-GA₁₂ derivatives, whereas in thegai mutant hydroxy-GA₂₄, hydroxy-GA₂₅, and hydroxy-GA₉ compounds were detected. Quantification of seven GAs by GC-selected ion monitoring (SIM), using internal standards, and comparisons of the ion intensities in the SIM chromatograms of the other thirteen GAs, demonstrated that thegai mutant had reduced levels of all C₂₀-dicarboxylic acids (GA₅₃, GA₄₄, GA₁₉, GA₁₂, GA₁₅, GA₂₄, GA₃₇, GA₂₇, and GA₃₆). In contrast,gai plants had increased levels of C₂₀-tricarboxylic acid GAs (GA₁₇, GA₂₅, and GA₄₁) and of all C₁₉-GAs (GA₂₀, GA₁, GA₈, GA₉, GA₅₁, GA₄, GA₃₄, and GA₇₁) except GA₂₉. The 3β-hydroxylated GAs, GA₁ and GA₄, and their respective 2β-hydroxylated derivatives, GA₈ and GA₃₄, were the most abundant GAs found in shoots of thegai mutant. Thus, thegai mutation inArabidopsis results in a phenotype that resembles GA-deficient mutants, is insensitive to both applied and endogenous GAs, and contains low levels of C₂₀-dicarboxylic acid GAs and high levels of C₁₉-GAs. This indicates that theGAI gene controls a step beyond the synthesis of an active GA. Thegai mutant is presumably a GA-receptor mutant or a mutant with a block in the transduction pathway between the receptor and stem elongation. We thank Dr. L.N. Mander, Australian National University, Canberra, for providing [²H]gibberellins, Dr. B.O. Phinney, University of California, Los Angeles, USA for [¹³C]GA₈, and Dr. D.A. Gage, MSU-NIH Mass Spectrometry Facility (grant No. DRR00480), for advice with mass spectrometry. This work was supported by a fellowship from the Spanish Ministry of Agriculture (I.N.I.A.) to M.T., by the U.S. Department of Energy under Contract DE-ACO2-76ERO-1338, and by U.S. Department of Agriculture grant No. 88-37261-3434 to J.A.D.Z.     

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.     

Identification of endogenous gibberellins, and metabolism of tritiated and deuterated GA4, GA9 and GA20, in Scots pine (Pinus sylvestris) shoots

The application of gibberellin A_4/7 (GA_4/7) to the stem of previous-year (1-year-old) terminal shoots of Scots pine (Pinus sylvestris) seedlings has been observed to stimulate cambial growth locally, as well as at a distance in the distal current-year terminal shoot, but the distribution and metabolic fate of the applied GA_4/7, as well as the pathway of endogenous GA biosynthesis in this species, has not been investigated. As a first step, we analysed for endogenous GAs and monitored the transport and metabolism of labelled GAs 4, 9 and 20. Endogenous GAs from the elongating current-year terminal shoot of 2-year-old seedlings were purified by column chromatography and high-performance liquid chromatography and analysed by combined gas chromatography-mass spectrometry (GC-MS). GAs 1, 3, 4, 9, 12 and 20 were identified in the stem, and GAs 1, 3 and 4 in the needles, by full-scan mass spectrometry (GAs 1, 3, 4, 9 and 12) or selected-ion monitoring (GA₂₀) and Kovats retention index. Tritiated and deuterated GA₄, GA₉ or GA₂₀ were applied around the circumference at the midpoint of the previous-year terminal shoot, and metabolites were extracted from the elongating current-year terminal shoot, the application point, and the 1-year-old needles and the cambial region above and below the application point. After purification, detection by liquid scintillation spectrometry and analysis by GC-MS, it was evident that, for each applied GA, unmetabolised [²H₂]GA and [³H]radioactivity were present in every seedling part analysed. Most of the radioactivity was retained at the application point when [³H]GA₉ and [³H]GA₂₀ were applied, whereas the largest percentage of radioactivity derived from [³H]GA₄ was recovered in the current-year terminal shoot. It was also found that [²H₂]GA₉ was converted to [²H₂]GA₂₀ and to both [²H₂]GA₄ and [²H₂]GA₁, [²H₂]GA₄ was metabolised to [²H₂]GA₁, and [²H₂]GA₂₀ was converted to [²H₂]GA₂₉. The data indicate that for Pinus sylvestris shoots (1) GAs applied laterally to the outside of the vascular system of previous-year shoots not only are absorbed and translocated extensively throughout the previous-year and current-year shoots, but also are readily metabolised, (2) the GA metabolic pathways found are closely related to the endogenous GAs identified, and (3) GA₉ metabolism follows two distinctly different routes: in one, GA₉ is converted to GA₁ through GA₄, and in the other it is converted to GA₂₀, which is then metabolised to GA₂₉. The results suggest that the late 13-hydroxylation pathway is an important route for GA biosynthesis in shoots of Pinus sylvestris, and that the stimulation of cambial growth in Scots pine by exogenous GA_4/7 may be due to its conversion to GA₁, rather than to it being active per se.     

The role of gibberellin biosynthesis in the control of growth and flowering in Matthiola incana

Recently, it was found that stem elongation and flowering of stock Matthiola incana (L.) R. Br. are promoted by exogenous gibberellins (GAs), including GA₄, and also by acylcyclohexanedione inhibitors of GA biosynthesis, such as prohexadione‐calcium (PCa) and trinexapac‐ethyl (TNE). Here, because it was unclear how GA biosynthetic inhibitors could promote stem elongation and flowering, their effect on GA biosynthesis has been examined by quantifying endogenous GA levels; also, the sensitivity of stem elongation and flowering to various GAs in combination with the inhibitors was examined. Stem elongation and flowering were most effectively promoted by GA₄ when combined with PCa and, next in order, by 2,2‐dimethyl‐GA₄, PCa, GA₄+TNE, TNE, GA₉+PCa and by GA₄. There was little or no promotion by GA₁, GA₃, GA₉, GA₁₃, GA₂₀ and 3‐epi‐2,2‐dimethyl‐GA₄. Both the promotive effects of the acylcyclohexanediones on stem elongation and flowering, particularly when applied with GA₄, and the fact that TNE caused a build‐up of endogenous GA₄ imply that one effect of TNE at the lower dose involved an inhibition of 2β‐hydroxylation of GA₄ rather than an inhibition of 20‐oxidation and 3β‐hydroxylation of GAs which were precursors of GA₄. Overall, these results indicate that: (1) GAs with 3β‐OH and without 13‐OH groups (e.g. GA₄) are the most important for stem elongation and flowering in M. incana; (2) growth promotion rather than inhibition can result if an acylcyclohexanedione acts predominantly to slow 2β‐hydroxylation and so slows inactivation of active gibbberellins, including GA₄. It follows that a low dose of an acylcyclohexanedione can be a ‘growth enhancer’ for any applied GA that is liable to inactivation by 2β‐hydroxylation.     

Biosynthesis of 12α-and 13-hydroxylated gibberellins in a cell-free system from Cucurbita maxima endosperm and the identification of new endogenous gibberellins

Gibberellin (GA) biosynthesis in cell-free systems from Cucurbita maxima L. endosperm was reinvestigated using incubation conditions different from those employed in previous work. The metabolism of GA₁₂ yielded GA₁₃, GA₄₃ and 12α-hydroxyGA₄₃ as major products, GA₄, GA₃₇, GA₃₉, GA₄₆ and four unidentified compounds as minor products. The intermediates GA₁₅, GA₂₄ and GA₂₅ accumulated at low protein concentrations. The structure of the previously uncharacterised 12α-hydroxyGA₄₃ was inferred from its mass spectrum and by its formation from both GA₃₉ and GA₄₃. Gibberellin A₃₉ and 12α-hydroxyGA₄₃ were formed by a soluble 12α-hydroxylase that had not been detected before. Gibberellin A₁₂-aldehyde was metabolised to essentially the same products as GA₁₂ but with less efficiency. A new 13-hydroxylation pathway was found. Gibberellin A₅₃, formed from GA₁₂ by a microsomal oxidase, was converted by soluble 2-oxoglutarate-dependent oxidases to GA₁ GA₂₃, GA₂₈, GA₄₄, and putative 2β-hydroxyGA₂₈. Minor products were GA₁₉, GA₂₀, GA₃₈ and three unidentified GAs. Microsomal 13-hydroxylation (the formation of GA₅₃) was suppressed by the cofactors for 2-oxoglutarate-dependent enzymes. Reinvestigation of the endogenous GAs confirmed the significance of the new metabolic products. In addition to the endogenous GAs reported by Blechschmidt et al. (1984, Phytochemistry 23, 553–558), GA₁, GA₈, GA₂₅, GA₂₈, GA₃₆, GA₄₈ and 12α-hydroxyGA₄₃ were identified by full-scan capillary gas chromatography-mass spectrometry and Kovats retention indices. Thus both the 12α-hydroxylation and the 13-hydroxylation pathways found in the cell-free system operate also in vivo, giving rise to 12α-hydroxyGA₄₃ and GA₁ (or GA₈), respectively, as their end products. Evidence for endogenous GA₂₀ and GA₂₄ was also obtained but it was less conclusive due to interference.     

Promotive and inhibitory effects of uniconazole and prohexadione on the sprouting of bulbils of Chinese yam,Dioscorea opposita

Gibberellin A₁ (GA₁), GA₃ and GA₄ inhibited the sprouting of nondormant bulbils of Chinese yam, Dioscorea opposita, where the effectiveness of the GAs was as follows: GA₄>GA₁+GA₃. Uniconazole and prohexadione, plant growth retardants, promoted the sprouting of half-dormant bulbils. By contrast, these retardants inhibited the sprouting of nondormant bulbils. Gibberellin A₃ (GA₃) and A₄ (GA₄) which were applied to the stems of the sprouted bulbils, promoted stem elongation, but GAs applied to the bulbous parts inhibited this process. The effectiveness of the GAs on stem elongation was as follows: GA₃+GA₄ for the promotion and GA₄ > GA₃ for the inhibition. Uniconazole applied to the stem inhibited the stem elongation of the sprouted bulbils. These results suggest the possible involvement of endogenous GAs in the induction and maintenance of bulbil dormancy of D. opposita, as well as in the bulbil sprouting and subsequent stem elongation.     

Gibberellin Metabolism and Transport During Germination and Young Seedling Growth of Pea (<Emphasis Type="Italic">Pisum sativum</Emphasis> L.)

The role of gibberellins (GAs) during germination and early seedling growth is examined by following the metabolism and transport of radiolabeled GAs in cotyledon, shoot, and root tissues of pea (Pisum sativum L.) using an aseptic culture system. Mature pea seeds have significant endogenous GA₂₀ levels that fall during germination and early seedling growth, a period when the seedling develops the capacity to transport GA₂₀ from the cotyledon to the shoot and root of the seedling. Even though cotyledons at 0–2 days after imbibition have appreciable amounts of GA₂₀, the cotyledons retain the ability to metabolize labeled GA₁₉ to GA₂₀ and express significant levels of PsGA20ox2 message (which encodes a GA biosynthesis enzyme, GA 20-oxidase). The large pool of cotyledonary GA₂₀ likely provides substrate for GA₁ synthesis in the cotyledons during germination, as well as for shoots and roots during early seedling growth. The shoots and roots express GA metabolism genes (PsGA3ox genes which encode GA 3-oxidases for synthesis of bioactive GA₁, and PsGA2ox genes which encode GA 2-oxidases for deactivation of GAs to GA₂₉ and GA₈), and they develop the capacity to metabolize GAs as necessary for seedling establishment. Auxins also show an interesting pattern during early seedling growth, with higher levels of 4-chloro-indole-3-acetic acid (4-Cl-IAA) in mature seeds and higher levels of indole-3-acetic acid (IAA) in young root and shoot tissues. This suggests a changing role for auxins during early seedling development.     

Aminooxyacetic acid inhibits antheridiogenesis and development of Anemia phyllitidis gametophytes

Cytomorphological studies of the development of young fern gametophytes (Anemia phyllitidis) have been used to investigate combined effects of gibberellic acid and ethylene on male sex expression. ACC (the key by-product in ethylene biosynthesis pathway) was found to exert a synergetic effect on the gibberellic acid-induced antheridia formation, and this phenomenon could be related with the specific stimulation of cell growth and activity of their differentiation. To complete and verify those observations male sex expression in the fern gametophytes treated with ACC-biosynthesis inhibitor was reinvestigated. Aminooxyacetic acid (AOA) restrained antheridia formation via inhibition of cell divisions. AOA influenced the arrangement and flexibility of cellulose microfibrils in the antheridial zone cells, thus affecting cell expansion. On the other hand, the level of DNA synthesis was not reduced. Transient increase in the number of S-phase cells, followed by the accumulation of G2-phase cells led to the enhancement of cell polyploidization. All these findings correspond with the previous observations and support participation of ethylene in gibberellic acid-induced male sex expression in ferns.Abbreviations AOA Aminooxyacetic acid - CPA Cell profile area - GA Gibberellin - GA₃ Gibberellic acid     

Gibberellins in Leaves of Alstroemeria hybrida: Identification and Quantification in Relation to Leaf Age

In alstroemeria (Alstroemeria hybrida), leaf senescence is retarded effectively by the application of gibberellins (GAs). To study the role of endogenous GAs in leaf senescence, the GA content was analyzed by combined gas chromatography and mass spectrometry. Five 13-hydroxy GAs (GA₁₉, GA₂₀, GA₁, GA₈, and GA₂₉) and three non-13-hydroxy GAs (GA₉ and GA₄) were identified in leaf extracts by comparing Kováts retention indices (KRIs) and full scan mass sprectra with those of reference GAs. In addition, GA₁₅, GA₄₄, GA₂₄, and GA₃₄ were tentatively identified by comparing selected ion monitoring results and KRIs with those of reference GAs. A number of GAs were detected in conjugated form as well. Concentrations of GAs in alstroemeria changed with the development of leaves. The proportion of biologically active GA₁ and GA₄ decreased with progressive senescence and the fraction of conjugated GAs increased. Received May 26, 1997; accepted August 12, 1997     

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.     

Gibberellins and the photosensitivity of isolated embryos from non-stratified apple seeds

Summary The phytochrome system is responsible for the photosensitivity of dormant, isolated apple embryos in culture. Maximum photosensitivity occurs on the second day of culture and it is unaffected by gibberellins (GAs) in concentrations below 10^-4M. Higher concentrations of GA decrease the photosensitivity.The endogenous quantities of GA₄ and GA₇ were determined in embryos grown at white light, in darkness and in darkness following an exposure to red light. The GA₇ level remained unaffected by the light conditions, whereas the amount of GA₄ was three times higher in light or red-light-treated cultures than in the dark grown ones.Similar experiments were done using AMO-1618, an inhibitor of GA biosynthesis, which is also a strong inhibitor of apple seed germination. In this case the level of both GA₄ and GA₇ was light-independent. These experiments suggest that the phytochrome system participates in the regulation of GAs biosynthesis by mediating one of the last steps of GA₄ formation.