Relations polyphenols-croissance: Lignification et limitation de croissance chez Lycopersicum esculentum

Abstract Polyphenols and growth – Lignification and limitation of growth in Lycopersicum esculentum. When fed with quinic acid, young tomato seedlings (Lycopersicum esculentum Mill. cv. St. Pierre) exhibited reduced growth and marked changes in cell wall composition: cellulose concentrations decreased whereas those of lignin increased. Exogenously supplied growth substances (IAA, GA₃) affected both the size of the plants and the lignification process: IAA treatments resembled quinic acid induced modifications with regard to both size and lignification: GA₃ applied to quinate treated plants counteracted the effects of this compound by reducing the lignin content and improving the growth. The possible effect of abnormal lignification as a limiting factor in cell growth is supported by the characterization of lignins in tissues different from xylem.     

Lignin synthesis and its related enzymes as markers of tracheary-element differentiation in single cells isolated from the mesophyll of Zinnia elegans

Mesophyll cells isolated from Zinnia elegans L. cv. Canary Bird were cultured for 96 h in a liquid medium containing 0.1 mg l^-1 -naphthaleneacetic acid and 1 mg l^-1 benzyladenine in which both differentiation of tracheary elements (TE) and cell division were induced, or in a medium containing 0.1 mg l^-1 -naphthaleneacetic acid and 0.001 mg l^-1 benzyladenine, in which cell division was induced but TE differentiation was not. Lignification was found to occur only in the former medium, fairly synchronously after 76 h of culture, 5 h later than the onset of visible secondary wall thickening. Changes in the soluble phenolics were not correlated with TE differentiation. Of three important enzymes which have been reported to play a role in TE differentiation, the activity of phenylalanine ammonia-lyase (EC 4.3.1.5) in the TE-inductive culture was higher than that in the control culture between 72 and 96 h of culture, when TE differentiation progressed and lignin was synthesized actively. O-Methyltransferase (EC 2.1.1.6) activity was higher in the control culture than in the TE-inductive culture, indicating that this enzyme was not a marker enzyme of TE differentiation. The activities of peroxidases (EC 1.11.1.7), one extractable and the other nonextractable, with CaCl₂ from the cell walls, reached peaks at 72 h (just before lignification) and 84 h of culture (active lignin synthesis), respectively, in the TE-inductive culture only, whereas the activity of soluble peroxidase showed a similar pattern of increase in the TE-inductive to the control culture. These results indicate that phenylalanine ammonia-lyase and peroxidase bound to the cell walls can be marker proteins for the differentiation of TE.Abbreviations OMT O-methyltransferase - PO peroxidase - PAL phenylalanine ammonia-lyase - TE tracheary element(s)     

The Role of Auxin and Gibberellin in Controlling Lignin Formation in Primary Phloem Fibers and in Xylem of Coleus blumei Stems

The hypothesis that auxin (IAA) and gibberellic acid (GA₃) control the formation of lignin is confirmed for the primary phloem fibers and for the secondary xylem in the stem of Coleus blumel Benth. Indoleacetic acid alone, or a combination of high IAA/low GA₃ (w/w), induced short phloem fibers with thick secondary walls, that contained lignin rich in syringyl units (high ratio of syringyl/guaiacyl). On the other hand, a combination of high GA₃/low IAA (w/w), which promoted the differentiation of long phloem fibers with thin walls, decreased the relative content of the syringyl units (low syringyl/guaiacyl ratio). In the secondary xylem, these hormonal treatments yielded only slight changes in the noncondensed monomeric guaiacyl units, confirming the relative stability of the guaiacyl lignification pattern in this tissue. In the xylem, indoleacetic acid alone, or a combination of high IAA/low GA₃ induced lignin poor in syringyl units (low syringyl/guaiacyl ratio). A combination of high GA₃/low IAA promoted a relatively slight increase in syringyl yield, indicating greater responsiveness of the syringyl lignification pattern to growth regulators. The possible functional and technological significance of our results is discussed.     

Production of gibberellins and indole-3-acetic acid by Rhizobium phaseoli in relation to nodulation of Phaseolus vulgaris roots

Similar ranges of gibberellins (GAs) were detected by high-performance liquid chromatography (HPLC)-immunoassay procedures in ten cultures of wild-type and mutant strains of Rhizobium phaseoli. The major GAs excreted into the culture medium were GA₁ and GA₄. These identifications were confirmed by combined gas chromatographymass spectrometry. The HPLC-immunoassays also detected smaller amounts of GA₉- as well as GA₂₀-like compounds, the latter being present in some but not all cultures. In addition to GAs, all strains excreted indole-3-acetic acid (IAA) but there was no obvious relationship between the amounts of GA and IAA that accumulated. The Rhizobium strains studied included nod ^– and fix ^– mutants, making it unlikely that the IAA- and GA-biosynthesis genes are closely linked to the genes for nodulation and nitrogen fixation.The HPLC-immunoassay analyses showed also that nodules and non-nodulated roots of Phaseolus vulgaris L. contained similar spectra of GAs to R. phaseoli culture media. The GA pools in roots and nodules were of similar size, indicating that Rhizobium does not make a major contribution to the GA content of the infected tissue.Abbreviations EIA enzyme immunoassay - GA_n gibberellin A_n - GC-MS gas chromatography-mass spectrometry - HPLC high-performance liquid chromatography - IAA indole-3-acetic acid - Me methyl ester - RIA radioimmunoassay - TLC thin-layer chromatography     

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.     

Pleiotropic effects of the<Emphasis Type="Italic"> male sterile33</Emphasis> (<Emphasis Type="Italic">ms33</Emphasis>) mutation in<Emphasis Type="Italic"> Arabidopsis</Emphasis> are associated with modifications in endogenous gibberellins,indole-3-acetic acid and abscisic acid

Earlier, we reported that mutation in the Male Sterile33 (MS33) locus in Arabidopsis thaliana causes inhibition of stamen filament growth and a defect in the maturation of pollen grains [Fei and Sawhney (1999) Physiol Plant 105:165–170; Fei and Sawhney (2001) Can J Bot 79:118–129]. Here we report that the ms33 mutant has other pleiotropic effects, including aberrant growth of all floral organs and a delay in seed germination and in flowering time. These defects could be partially or completely restored by low temperature or by exogenous gibberellin A₄ (GA₄), which in all cases was more effective than GA₃ Analysis of endogenous GAs showed that in wild type (WT) mature flowers GA₄ was the major GA, and that relative to WT the ms33 flowers had low levels of the growth active GAs, GA₁ and GA₄, and very reduced levels of GA₉, GA₂₄ and GA₁₅, precursors of GA₄. This suggests that mutation in the MS33 gene may suppress the GA biosynthetic pathway that leads to GA₄ via GA₉ and the early 13-H C₂₀ GAs. WT flowers also possessed a much higher level of indole-3-acetic acid (IAA), and a lower level of abscisic acid (ABA), relative to ms33 flowers. Low temperature induced partial restoration of male fertility in the ms33 flowers and this was associated with partial increase in GA₄. In contrast, in WT flowers GA₁ and GA₄ were very much reduced by low temperature. Low temperature also had little effect on IAA or ABA levels of ms33 flowers, but did reduce (>2-fold) IAA levels in WT flowers. The double mutants, ms33 aba1-1 (an ABA-deficient mutant), and ms33 spy-3 (a GA signal transduction mutant) had flower phenotypes similar to ms33. Together, the data suggest that the developmental defects in the ms33 mutant are unrelated to ABA levels, but may be causally associated with reduced levels of IAA, GA₁ and GA₄, compared to WT flowers.Abbreviations ABA Abscisic acid - GA Gibberellin - GC-MS-SIM Gas chromatography-mass spectrometry-selected ion monitoring - IAA Indole-3-acetic acid - ms33 Male sterile33 mutant - PP333 Paclobutrazol - WT Wild type     

Transgenic modification of gai or rgl1 causes dwarfing and alters gibberellins, root growth, and metabolite profiles in Populus

In Arabidopsis and other plants, gibberellin (GA)-regulated responses are mediated by proteins including GAI, RGA and RGL1-3 that contain a functional DELLA domain. Through transgenic modification, we found that DELLA-less versions of GAI (gai) and RGL1 (rgl1) in a Populus tree have profound, dominant effects on phenotype, producing pleiotropic changes in morphology and metabolic profiles. Shoots were dwarfed, likely via constitutive repression of GA-induced elongation, whereas root growth was promoted two- to threefold in vitro. Applied GA₃ inhibited adventitious root production in wild-type poplar, but gai/rgl1 poplars were unaffected by the inhibition. The concentrations of bioactive GA₁ and GA₄ in leaves of gai- and rgl1-expressing plants increased 12- to 64-fold, while the C₁₉ precursors of GA₁ (GA₅₃, GA₄₄ and GA₁₉) decreased three- to ninefold, consistent with feedback regulation of GA 20-oxidase in the transgenic plants. The transgenic modifications elicited significant metabolic changes. In roots, metabolic profiling suggested increased respiration as a possible mechanism of the increased root growth. In leaves, we found metabolite changes suggesting reduced carbon flux through the lignin biosynthetic pathway and a shift towards allocation of secondary storage and defense metabolites, including various phenols, phenolic glucosides, and phenolic acid conjugates.     

Gibberellins in seeds of Arabidopsis thaliana: biological activities,identification and effects of light and chilling on endogenous levels

The activities of several gibberellins in stimulating germination of wild-type and GA-deficient gal seeds of Arabidopsis thaliana were compared. Of the six compounds tested GA₄ and GA₇-isolactone had the highest activity and GA₇ and GA₉ the lowest; activities of GA₁ and GA₃ were intermediate. Combined application of pure GAs presented no indications that more than one GA receptor is involved. Four GAs were identified in extracts from wild-type and GA-insensitive gai seeds by combined gas chromatography mass spectrometry: GA₁, GA₃, GA₄ and GA₉. Effects of light and chilling on levels of GA₁, GA₄ and GA₉ were studied using deuterated standards. Light increased both GA levels and germination in unchilled wild-type and gai seeds. As a result of irradiation GA levels in gai seeds were 7–10 times as high as in wild-type seeds. In the dark germination was 0%, in the light 14% of gai seeds and 95% of wild-type seeds germinated. A chilling pre-treatment of 7 days at 2°C was required to enhance further the germination of gai seeds in the light. Light did not increase GA levels of chilled seeds of either genotype; levels of GA₄ and GA₉ of chilled gai seeds, in the light were respectively 7 and 12 times lower than in non-chilled seeds, whereas the latter seeds germinated better. Slightly elevated levels of GA₄ were detected in darkness after chilling, but germination capacity was still 0%. These results strengthened the conclusion that GAs are required for germination of A. thaliana seeds, whereby GA₄ has intrinsic biological activity. However, it is unlikely that light and chilling stimulate germination primarily by increasing levels of GA. Instead GA sensitivity is a possible alternative.     

The source of gibberellins in the parthenocarpic development of ovaries on topped pea plants

The role and source of gibberellins (GAs) involved in the development of parthenocarpic fruits of Pisum sativum L. has been investigated. Gibberellins applied to the leaf adjacent to an emasculated ovary induced parthenocarpic fruit development on intact plants. The application of gibberellic acid (GA₃) had to be done within 1 d of anthesis to be fully effective and the response was concentration-dependent. Gibberellin A₁ and GA₃ worked equally well and GA₂₀ was less efficient. [³H]Gibberellin A₁ applied to the leaf accumulated in the ovary and the accumulation was related to the growth response. These experiments show that GA applied to the leaf in high enough concentration is translocated to the ovary. Emasculated ovaries on decapitated pea plants develop without application of growth hormones. When [³H] GA₁ was applied to the leaf adjacent to the ovary a substantial amount of radioactivity accumulated in the growing shoot of intact plants. In decapitated plants, however, this radioactivity was mainly found in the ovary. There it caused growth proportional to the accumulation of CA₁. Application of LAB 150978, an inhibitor of GA biosynthesis, to decapitated plants inhibited parthenocarpic fruit development and this inhibition was counteracted by the application of GA₃ (either to the fruit, or the leaf adjacent to the ovary, or through the lower cut end of the stem). All evidence taken together supports the view that parthenocarpic pea fruit development on topped plants depends on the import of gibberellins or their precursors, probably from the vegetative aerial parts of the plant.Abbreviations FW flesh weight - GA_n gibberellin A_n - HPLC high-performance 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     

Gibberellins in shoots of Hordeum vulgare. A comparison between cv. Triumph and two dwarf mutants which differ in their response to gibberellin

The gibberellin (GA) content of barley (Hordeum vulgare L.) cv. Triumph was analysed by full scan gas chromatography-mass spectrometry. Developing grain contained several di-, tri-, and tetra-hydroxylated GAs, with the most abundant ones being hydroxylated at C-2, C-3, C-12β, and/or C-18. In contrast, the only GAs to be detected in shoots of 9-day old dark- and light-grown seedlings of Triumph were 13-hydroxylated C₁₉-GAs, namely GA₁, GA₈, GA₂₀, and GA₂₉, (all of which are components of the early 13-hydroxylation GA biosynthetic pathway) and GA₃. Feeds of [¹³C.³H₂GA₂₀, confirmed that GA₂₀ is a precursor of GA₁, GA₈, and GA₂₉ in barley shoots. From these results it is suggested that stem growth of barley, in common with that of several other mono- and dicotyledons, is controlled by GA,. Homozygous gal and gal lines were obtained after backcrossing to Triumph. These were then compared to Triumph with respect to their GA content and response to applied GAs and GA precursors. Shoots of the homozygous gal gal plants contained ca 6-fold less GA₁, than Triumph. These plants responded to all ent-kaurenoids and 13-hydroxylated C₂₀- and C₁₉-GAs tested. It is concluded that the gal locus impairs the GA biosynthetic pathway prior to ent-kaurene, most probably at ent-kaurene synthetase. In contrast, shoots of homozygous gal gal line contained ca 10-fold higher levels of GA, than Triumph, but failed to respond to applied GA, or GA₃. The gal locus therefore confers insensitivity to both exogenous and endogenous GAs, possibly by perturbing the reception or transduction of the GA₁ signal.     

Gibberellins and bud break,vegetative shoot growth and flowering in Metrosideros collina cv. Tahiti

Applications of the growth promotive gibberellins (GAs) GA₄ and 2,2-dimethyl GA₄, and of C-16,17 endo-dihydro GA₅, which is known to promote flowering while inhibiting stem growth in the long-day grass Lolium temulentum, were made to micropropagated plants of Metrosideros collina cv. Tahiti, a highly ornamental cultivar with an intermittent flowering pattern. Gibberellin A₄ and 2,2-dimethyl GA₄ stimulated vegetative growth both in elongating shoots, and internodes of shoots developing from buds that were quiescent at the time of GA application. Abscission of the apices of expanding shoots, a feature of mature Metrosideros plants, was inhibited by these GAs, the rejuvenation of micropropagated plantlets being enhanced. However, C-16,17 endo-dihydro GA₅ differed from GA₄ and 2,2-dimethyl GA₄ by having no promotive effects on vegetative growth, and no inhibition of apical abscission. Notwithstanding this contrasting effect on vegetative growth, high doses of GA₄ or C-16,17 endo-dihydro GA₅ similarly reduced flowering on shoots to which either GA was applied. Reduced flowering in response to applied GAs is common in many woody angiosperms, and in this instance was probably the combined result of abortion of developing floral structures in quiescent buds, and a preferential inhibition of bud break for floral buds relative to vegetative buds, particularly by GA₄. Finally, both C-16,17 endo-dihydro GA₅ and GA₄ strongly inhibited bud break in this woody angiosperm, although GA₄ could initially stimulate bud break when applied to vegetative buds close to the expansion stage. The above findings, in toto, highlight the sensitivity of Metrosideros to both classes of GA in a variety of growth and development processes.     

The brassinosteroid growth response in pea is not mediated by changes in gibberellin content

The objective of this study was to increase our understanding of the relationship between brassinosteroids (BRs) and gibberellins (GAs) by examining the effects of BR deficiency on the GA biosynthesis pathway in several tissue types of pea (Pisum sativum L.). It was suggested recently that, in Arabidopsis, BRs act as positive regulators of GA 20-oxidation, a key step in GA biosynthesis [Bouquin et al. (2001) Plant Physiol 127:450–458]. However, this may not be the case in pea as GA₂₀ levels were consistently higher in all shoot tissues of BR-deficient (lk and lkb) and BR-response (lka) mutants. The application of brassinolide (BL) to lkb plants reduced GA₂₀ levels, and metabolism studies revealed a reduced conversion of GA₁₉ to GA₂₀ in epi-BL-treated lkb plants. These results indicate that BRs actually negatively regulate GA₂₀ levels in pea. Although GA₂₀ levels are affected by BR levels, this does not result in consistent changes in the level of the bioactive GA, GA₁. Therefore, even though a clear interaction exists between endogenous BR levels and the level of GA₂₀, this interaction may not be biologically significant. In addition to the effect of BRs on GA levels, the effect of altered GA₁ levels on endogenous BR levels was examined. There was no significant difference in BR levels between the GA mutants and the wild type (wt), indicating that altered GA₁ levels have no effect on BR levels in pea. It appears that the BR growth response is not mediated by changes in bioactive GA levels, thus providing further evidence that BRs are important regulators of stem elongation.     

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.     

Tracheary element differentiation in Zinnia mesophyll cell cultures

Mechanically isolated mesophyll cells of Zinnia elegans differentiate into tracheary elements (TEs) when cultured in a medium containing adequate auxin and cytokinin. Differentiation in this culture system is relatively synchronous, rapid (occuring within 3 days of cell isolation) and efficient (with up to 65% of the mesophyll cells differentiating into TEs), and does not require prior mitosis. The Zinnia system has been used to investigate (a) cytological and ultrastructural changes occurring during TE differentiation, such as the reorganization of microtubules controlling secondary wall deposition, (b) the influences of calcium and of various plant hormones and antihormones on TE differentiation, and (c) biochemical changes during differentiation, including those occurring during secondary wall deposition, lignification and autolysis. This review summarizes experiments in which the Zinnia system has served as a model for the study of TE differentiation.     

Abscisic acid and gibberellin-like substances in roots and root nodules ofGlycine max

Summary The content of endogenous gibberellin (GA)-like substances of roots and root nodules of SOya, and GA production byRhizobium japonicum cultures, were investigated by a combined thin layer chromatographic (TLC)-dwarf pea epicotyl bioassay technique. GAs were more concentrated in root nodules than in the roots, totalling 1.34 and 0.16 nM GA₃ equivalents g⁻¹ dry wt. respectively. GA production byR. japonicum cultures was demonstrated (1.00 nM GA₃ equivalentsl ⁻¹) and comparison of the GA components of plant and bacterial culture medium extracts, suggested that rhizobial GA production may contribute to the nodule GA content. Cis-trans abscisic acid (ABA) was identified in root and nodule extracts by TLC-gas liquid chromatography (GLC), and amounted to 0.18 and 2.21 nM g⁻¹ dry wt. respectively, whereas 0.30 and 4.63 nM ABA equivalents g⁻¹ dry wt. were detected by a TLC-wheat embryo bioassay technique. ABA was not detected in extracts of bacterial cultures.     

Endogenous gibberellin- and cytokinin-like substances in cultured shoot tissues of apple,Malus pumila cv. Jonathan,in relation to adventitious root formation

The frequencies of adventitious root formation in vitro of isolated shoots from bud cultures of apple (Malus pumila cv. Jonathan) after 1, 7 and 31 subcultures (weeks 5, 29 and 109 after the initial culture) were 5, 78 and 95% respectively. Endogenous gibberellin-like substances (GA) were extracted, chromatographed on SiO₂ partition columns, and assayed on dwarf rice (Oryza sativa cv. Tan-ginbozu). The levels of GA in shoots from the 1st, 7th and 31st subcultures were 40, 19 and 14 ng GA₃ eq./g dry weight of tissue, respectively, a trend which suggests an inverse relationship between endogenous GA level and rooting ability. This is consistent with the fact that applied GA₃ inhibits rooting in apple and many other species. The major peak of GA activity eluted coincidentally with GA₁/GA₃/GA₁₉. Endogenous cytokinin-like substances (CK) were chromatographed on paper and assayed with soybean hypocotyl sections. In contrast to the decrease in GA activity, CK activity increased 1.5–2.7 fold in the later subcultures (cytokinin activity per shoot, however, declined).     

Identification of gibberellins in the rice plant and quantitative changes of gibberellin A19 throughout its life cycle

The major endogenous gibberellin (GA) in shoots, roots and ears of the rice plant, Oryza sativa L. japonica cv. Nihonbare, was identified as GA₁₉ by combined gas liquid chromatography-mass spectrometry (GC-MS) and GC-selected ion current monitoring (GC-SICM). Another GA present in these tissues in small quantity was tentatively identified as GA₁ by GC-SICM, and GA₄ may be present in the seeds (kernels) of 3rd-leaf-stage seedlings. Using GC-SICM, the GA₁₉ content was quantified throughout the life cycle of rice plants. It was found to reach high levels (ca. 10–15 g/kg fresh weight) in 3rd-leaf seedlings, at panicle initiation (shoots), and during heading and anthesis (ears). The levels of GA₁₉ in Oryza sativa indica cv. T-136 underwent changes closely similar to those found in Nihonbare. The growth-promoting activity in rice of exogenous GA₁₉ is generally considerably less than that of GA₁. It therefore seems possible that GA₁₉ functions as a pool GA. The level of active GAs such as GA₁ may be regulated by the rate of biosynthesis of GA₁₉ or its metabolic conversions.Abbreviations GA(s) gibberellin(s) - GA_n gibberellin A_n - GA_n-MeTMS trimethylsilyl ether of GA_n methyl ester - GC-MS combined gas liquid chromatography-mass spectrometry - GC-SICM combined gas liquid chromatography-selected ion current monitoring - TLC thin-layer chromatography     

Inhibition of GA3-induced antheridiogenesis in Anemia phyllitidis by peptidic extracts from male sex organs of Chara

Low molecular weight peptidic component extracted from maturing male sex organs of Chara tomentosa, capable of inducing increased condensation of chromosomes and profound changes in the cell cycle progression, was applied to gametophytes of Anemia phyllitidis. Morphogenetic effects were studied with regard to cell divisions and GA₃-induced antheridiogenesis. As compared with both the GA ₃ ⁻ and GA ₃ ⁺ control samples, the extract-treated prothallia exhibited considerably lowered number of cells and altered morphology. Antheridial differentiation in prothallia of A. phyllitidis was severely inhibited when peptidic extract was added to medium containing GA₃. Considering endocytotic uptake, evidenced in root meristems, and those effects which have been observed in plant and human cells, the activity of extracts obtained from male sex organs of Chara may be interpreted as inhibitory influence acting via repression or modification of the genetic device of the cells rather, than a direct consequence of the retardation of cell division cycles.