Cellular Growth in Roots of a Gibberellin-Deficient Mutant of Tomato (Lycopersicon esculentum Mill.) and its Wild-type

The role of gibberellins in regulating the growth of tomatoroots was investigated by comparing various cellular parametersin cultured roots of the gibberellin-deficient mutant gib-l/gib-lwith those in roots of the near-isogenic wild-type. In addition,wild-type roots treated with 0?1 µM 2S,3S paclobutrazol,an inhibitor of gibberellin biosynthesis, and mutant roots treatedwith 0?1 µM GA₃ were also compared: the former roots constitutea phenocopy of the mutant, whereas the latter roots appear tobe ‘normalized’ and similar to wild-type. The elongationof mutant and phenocopied roots were similar, their maximumelongation rates being about half or two-thirds that of wild-typeor GA₃-treated mutant roots, respectively. These rates wereinterpreted in terms of the numbers and lengths of cells withinthe meristematic and non-meristematic portions of the elongationzone. Mean meristem length tended to be shorter in both themutant and the 2S,3S paclobutrazol-treated wild-type roots thanin the other two types of root. A major difference between thetwo pairs of mutant and normal roots was their mean final celllengths: mean lengths of cortical cells of the mutant and 2S,3Spaclobutrazol-treated roots were, respectively, 39% and 25%shorter than the mean length of wild-type roots. Final celllength in the GA³-treated mutant roots were similar to wild-type.By contrast, the diameters of mature cortical cells of the mutantand phenocopy were about 20% greater than the diameters of equivalentwild-type or ‘normalized’ mutant cells. The meanvolumes of cortical cells in all four types of roots showedno significant differences. Knowledge of the distribution ofcortical cell lengths, widths and volumes along the root axis,together with information about the rate of root elongation,permitted comparisons of the relative elemental growth ratesof each of these three cellular parameters. The available evidence suggests that the level of endogenousgibberellins in mutant roots is lower than in wild-type roots.The present results, therefore, suggest that endogenous gibberellinsare necessary for normal growth of cultured tomato roots andthat they regulate the relative amounts of growth at the longitudinaland transverse walls of the cells which, in turn, affects theshape of the elongating cells. Key words: Cell growth, cultured roots, gibberellin, gib-l mutant, Lycopersicon esculentum, 2S,3S paclobutrazol, relative elemental growth rate, root meristem     

The Meristem and Quiescent Centre in Cultured Root Apices of the gib-l Mutant of Tomato (Lycopersicon esculentum Mill.)

Cultured root apices of tomato bearing the gib-I mutation, whichreduces the levels of endogenous gibberellins, grew slower andwere thicker than wild-type contols. This was the result ofshorter and broader cells in the menstem of the mutant. Cellsof both cortex and stele were affected, but this did not causeany alteration to the volume fraction occupied by these twotissues in the root meristem. Root caps were longer in the mutantand there were also more layers of rhizodermis. All these effectscould be reproduced in wild-type roots by addition of 0.1µM2S, 3S paclobutrazol (an inhibitor of gibberellin biosynthesis)to the culture medium and could be normalized in mutant rootsby 0.1 µM GA₃. Cell doubling times in the proximal regionof the meristem were similar in mutant and wild-type roots,but were faster in both the quiescent centre (QC) and the capmeristem of the mutant. This latter feature of the mutant rootsis likely to be the cause of their longer caps, while the fasterrate of division in the QC accounts for the additional tiersof cells that were found to build up in the cortical portionof this zone These additional tiers failed to form in mutantroots grown in GA₃, but they could be induced in wild-type rootsby 2S, 3S paclobutrazol. These results suggest that endogenousgibberellins may be partly responsible for the slow rate ofcell growth and proliferation in the QC. Gibberellins, gib-I mutation, Lycopersicon esculentum, meristem, roots, 2S, 3S paclobutrazol, quiescent centre, tomato     

Effect of the Rht3 dwarfing gene on dynamics of cell extension in wheat leaves, and its modification by gibberellic acid and paclobutrazol

The second leaf of wheat was used as a model system to examinethe effects of the Rht3 dwarfing gene on leaf growth. Comparedto the rht3 wild type, the Rht3allele decreased final leaf length,surface area and dry mass by reducing the maximum growth rates,but without affecting growth duration. Gibberellic acid (GA₃)increased final leaf length and maximum growth rate in the rht3wild type, but was without effect on the Rht3 mutant, whichis generally regarded as being non-responsive to gibberellin(GA). Paclobutrazol, an inhibitor of GA biosynthesis, decreasedfinal leaf length and maximum growth rate in the rht3 wild typeto values similar to those in the untreated Rht3 mutant. NeitherGA₃ nor paclobutrazol affected the duration of leaf growth.The decrease in leaf length was produced by reduction of celllength rather than cell number. The maximum relative elementalgrowth rate (REGR) for cell extension was essentially the samein all treatments, as was the time between the cells leavingthe meristem and achieving maximum extension rate. The differencesbetween the genotypes and treatments were all almost entirelydue to differences in the time taken from the attainment ofmaximum REGR of cell extension to the cessation of extension.This was reflected in the length of the extension zone, whichwas approximately 6–8 per cent of final leaf length. Theeffects of the Rht3 allele, GA₃ and paclobutrazol all appearto be on the processes which promote the cessation of cell elongation. Key words: Cell extension, gibberellin, leaf growth, Rht3 gene, Triticum, wheat     

Effects Produced on Tomato Plants, Lycopersicum esculentum, by Seed or Root Treatment with Gibberellic Acid and Indol-3yl-Acetic Acid

Growth in lengths of tomato stems and leaves was acceleratedby 5.0 µg gibberellic acid (GA₂) applied to the seed,or by 5.0, 0.5, and 0.05 µg given to the roots. Treatmentwith 5.0 µg also decreased bud number and lengthened thetime between bud appearance and fruit formation on the firsttruss by 1–8 days. Smaller amounts applied to roots shortenedthis time by 1–4 days. Indol-3yl-acetic acid at 0.5 µghad no effect, nor was simultaneous application of GA₃ and IAAto the roots more effective than GA₃, alone. Single applicationsof very small amounts of GA₃ to seeds or seedling roots thusproved capable of changing growth-rates of stems, leaves, andtrusses.The effects of treating tomatoes with GA₂ and with culturesof Azotobacter chroococcum, which contain small amounts of GA₃,and IAA, are compared.     

Effects of Gibberellins on Seed Germination of Phytochrome-Deficient Mutants of Arabidopsis thaliana

Experiments were carried out to explore the involvement of gibberellins(GAs) in the light-induced germination of Arabidopsis thaliana(L.) Heynh, using wild type (WT) and phytochrome-deficient mutants(phyA, phyB and phyAphyB deficient in phytochrome A, B and Aplus B, respectively). Seed germination of WT and phytochrome-deficientmutants was inhibited by uniconazole (an inhibitor of an earlystep in biosynthesis of GA, the oxidation of ent-kaurene) andprohexadione (an inhibitor of late steps, namely, 2rß-and 3rß-hydroxylation). This inhibition was overcomeby simultaneous application of 10^-5 M GA₄. The relative activityof GAs for promoting germination of uniconazole-treated seedswas GA₄>GA₁=GA₉>GA₂₀. The wild type and the phyA and phyBmutants had an increased response to a red light pulse in thepresence of GA₁, GA₄, GA₉, GA₂₀ and GA₂₄ but there were no significantdifferences in activity of each GA between the mutants. Therefore,neither phytochrome A nor hytochrome B appears to regulate GAbiosynthesis from GA₁₂ to GA₄ during seed germination, sincethe conversion of GA₁₂ to GA₉ is regulated by one enzyme (GA20-oxidase). However, GA responsiveness appears to be regulatedby phytochromes other than phytochromes A and B, since the phyAphyBdouble mutant retains the photoreversible increased responseto GAs after a red light pulse. (Received February 13, 1995; Accepted July 11, 1995)     

Partial Purification and Characterization of Gibberellin 3{beta}-hydroxylase from Immature Seeds of Phaseolus vulgaris L.

Gibberellin 3/ß-hydroxylase,a 2-oxoglutarate-dependentdioxygenase that catalyzes the hydroxylation of GA₂₀ to GA₁,was purified 313-fold from immature seeds of Phaseolus vulgarisL. The mol wt of the enzyme was estimated to be 42,000 by gelfiltration HPLC and SDS-polyacrylamide gel electrophoresis.The enzyme exhibited maximum activity at pH 7.7. The Km valuesfor [2,3-³H]GA20 and [2,3-³H]GA, were 0.29µu and 0.33µm, respectively. The enzyme requires 2-oxoglutarate asa cosubstrate; the K_m value for 2-oxoglutarate was 250µMusing [³H]- GA₂₀ as a substrate. Fe²⁺ and ascorbate significantlyactivated the enzyme at all purification steps, while catalaseand BSA activated the purified enzyme only. The enzyme was inhibitedby divalent cations Mn²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺ and Hg²⁺.3ß-Hydroxylation of [³H]- GA₂₀ was also inhibitedby non-radioactive GA₅, GA₉,GA₁₅, GA₂₀ and GA₄₄. The possiblesite of 3ß-hydroxylation in gibberellin biosynthesisis discussed in terms of the substrate specificity of partiallypurified gibberellin 3ß-hydroxylase. (Received February 29, 1988; Accepted June 3, 1988)     

Principal directions of growth and the generation of cell patterns in wild-type and gib-1 mutant roots of tomato (Lycopersicon esculentum Mill.) grown in vitro

The patterns of cell growth and division characteristic of the apex of tomato roots grown in vitro were simulated by computer using a growth tensor (GT). The GT was used to clarify the basis of the altered cell patterns found within apices of roots whose gibberellin levels had been depressed by mutation (at the GIB-1 locus) or through application of the gibberellin-biosynthesis inhibitor, 2S,3S paclobutrazol. At the pole of wild-type roots, where the cell files of the cortex converge, there are commonly only one or two tiers of cortical cells sandwiched between the pole of the stele and the cap initials. By contrast, root apices of the gib-1 mutant contain additional tiers in this region. The development of these additional tiers is suppressed when roots of the mutant are grown in the presence of gibberellic acid (GA₃), but could be induced in wild-type roots when they are grown in 2S,3S paclobutrazol. The wild-type cell pattern can be simulated using the GT and by the application of appropriate rules that govern cell growth and division. The induced variations in cell pattern are interpreted as being due to displacements, within the apex, of the principal directions of growth (PDGs), which are represented, in part, by the set of periclines and anticlines seen in the cell wall network; these, in turn, are utilized in the specification of the GT. During normal (wild-type) root growth, the PDGs maintain a stable pattern and the corresponding cell pattern is also stable. However, in order to interpret the cellular behaviour found in wild-type roots grown in 2S, 3S paclobutrazol, simulation using the GT shows that, if the pattern of PDGs is destabilized and displaced distally along the root axis, the cell pattern reorganizes into that typical of gib-1 mutant roots. Conversely, the cell pattern of gib-1 roots, which reverts to wild-type upon exposure to GA₃, can be simulated if the PDGs are displaced proximally to the inside of the apex whereupon the number of cortical tiers at the root pole decreases. These results suggest a link between endogenous gibberellin level and the specification of the PDGs in the growing tomato root apex. Furthermore, the evidence of cell patterns from gib-1 roots suggests that, in order to achieve stability of PDGs with concomitant stable cellular patterning, an optimal gibberellin level is necessary. In practice, this can be attained by culturing the mutant roots in medium containing 1 M GA₃.Abbreviations GA₃ gibberellic acid - GT growth tensor - NCS natural coordinate system - PDG principal direction of growth - QC quiescent centre - RERG relative elemental rate of growth We are grateful to the former Agricultural and Food Research Council for financial support under the International Scientific Interchange Scheme to enable J.N. to work at Long Ashton Research Station, and to K. Kurczyski (Silesian University, Katowice, Poland) for help in writing a computer program for cell proliferation. Preparation of the model for growth and division was supported in part by a grant from the Committee for Scientific Research, Poland.     

Distribution of Radioactivity from Exogenously Supplied [1-14C]Indol-3-yl-acetic Acid and [3, 4-3H (N)] Gibberellin A, in Geotropically-stimulated Picea abies (L.) Karst. Roots

The distribution of exogenously-supplied radioactive labelledindol-3-yl-acetic acid (IAA) and gibberellin A₁ (GA₁) in geotropicallystimulated roots of Norway spruce (Picea abies (L.) Karst.)has been demonstrated. Seedlings were positioned with theirroot tips in 2.1 x 10^–6 M [¹⁴C]IAA or 1.3 x 10^–8m ³H-GA₁ for 4 and 20 h, respectively. After geotropic stimulationfor 90 min in the horizontal position the root tips were cutlongitudinally in 50 µm thick sections, using a freeze-microtome.The radioactivity in the ¹⁴C-IAA treated roots occurred in higherconcentration in the lower than in the upper halves (ratio 1.25:1). A similar trend was observed in the [³H]GA₁-treated rootswhere the ratio lower: upper halves was 2.04: 1. The ratio ofradioactivity in right and left halves of vertical roots wasapproximately the same in roots supplied with [¹⁴C]IAA and [³H]GA₁(1.09: 1). The supplied radioactive compounds were analysed chromatographicallyafter extraction in methanol of 6 mm apical root segments. Onlya small fraction (7–8 per cent) of the supplied [¹⁴C]IAAwas revealed unchanged in the segments. The major part of thechromatographed, labelled compound has not been identified,but on basis of its R_F value it is suggested that it may beindol-3-acetyl-aspartic acid (IAAasp). The chromatographic analysis of the [³H]GA,-treated segmentsshowed that only small fractions of this gibberellin has beenconverted to other compounds. These results have been discussed and correlated with knowledgeof plant growth regulators and their participation in root geotropism. Picea abies, spruce, geotropism, gibberellin A₁, indol-3-yl-acetic acid, growth regulators, redistribution in roots     

Interaction of a Brassinosteroid with IAA and GA3 in the Elongation of Cucumber Hypocotyl Sections

A synthetic brassinosteroid, 22,23(S,S)-homobrassinolide (hBR),was examined for its interaction with IAA and GA₃ in the elongationof hypocotyl sections of light-grown cucumber (Cucumis salivusL. cv. Aonagajibai) seedlings. hBR alone was less active thanIAA. Its optimal concentration was around 10 µM and thelowest effective concentration between 10 and 100 µM,which is more than 100 times higher than that of brassinolide.hBR was more active in sections from younger seedlings. Itsgrowth-promoting effect was negated or greatly reduced by inhibitorsof auxin-induced elongation such as p-chlorophenoxyisobutyricacid and kinetin. hBR acted synergistically with IAA and 2,4-Dbut not with GA₃ showing only an additive effect. Sequentialtreatment of sections with hBR and then with IAA also resultedin synergistic enhancement of auxininduced elongation, but whenthe order of treatment was reversed, hBR was inactive. The synergisticeffect was obtained with 1 h pretreatment with hBR and couldbe reduced by subsequent washing with water. There was no sequentialinteraction between hBR and GA₃. The synergistic pretreatmenteffects of hBR and GA₃ were simply additive to each other. Amembrane-bound ATPase inhibitor, dicyclohexylcarbodiimide, inhibitedthe hBR-induced elongation, but did not affect GA₃-induced elongation.The findings led to the conclusion that brassinosteroids enhanceauxin action and possess growth-promoting activity which isindependent of that of gibberellin. (Received November 9, 1984; Accepted February 18, 1985)     

Amounts of Nuclear DNA and Internal Morphology of Gibberellin- and Abscisic Acid-deficient Tomato (Lycopersicon esculentum Mill.) Seeds During Maturation, Imbibition and Germination

Using X-ray photography and flow cytometry, the internal morphologyand DNA replication activity of wild type (wt), GA- (gib-1 )and ABA-deficient (sit^w ) tomato (Lycopersicon esculentum Mill.cv. Moneymaker) mutant seeds were studied. During seed formation,from 30 to 45 d after pollination (DAP) the endosperm becomessolid and the seed starts to gain desiccation tolerance. Atthis time significant changes occur in the amounts of DNA inradicle tip cells. At 30 DAP, radicle tip cells of the threegenotypes manifest about 60% of 2C, 30% of 4C and 10% of 8Camounts of DNA. Upon maturation (45 DAP onwards), most cellsin the seeds of the three genotypes arrest in the G₁phase ofthe cell-cycle with 2C amounts of DNA. However, a relativelyhigh proportion of cells with 4C amounts of DNA was detectedin the radicle tip cells ofsit^w compared with wild type andgib-1. At the well-matured stage (60 DAP), there were about 2% ofseeds with free space in wild type andgib-1 , and about 13%insit^w . At the over-matured stage (75 DAP), even more seedswith free space were found insit^w , whereas no increase in theproportion of the seeds with free space was detected in theother two genotypes. In -1.0 MPa PEG-6000 with or without 10µM GA₄₊₇, no germination occurred in well-matured wildtype andgib-1 seeds, whether or not they were dried after harvest.However,sit^w seeds were able to germinate both in over-maturefruit and in -1.0 MPa PEG-6000. Priming of dried seeds in -1.0MPa PEG induced a large amount of free space in almost all seedsof the three genotypes, and nuclear DNA synthesis in the radicletip cells of wild type andsit^w seeds. However, PEG priming offresh (non-dried) seeds had no effect on the amount of freespace and 2C/4C DNA ratios in wild type orgib-1 seeds, but didinduce free space in about 20–25% ofsit^w seeds and provoked4C signals insit^w seeds. Removal of the endosperm and testaopposite the radicle tip of seeds resulted in root protrusion,the induction of free space and an increase of 4C DNA signalsin the three genotypes. It is concluded that ABA is crucialfor the efficient arrest of tomato embryo radicle tip cellsin G₁phase upon maturation, whereas GAs play an important rolein re-initiating 4C DNA levels upon germination. Dormancy; flow cytometry; free space; Lycopersicon esculentum ; maturation; priming; seed; tomato     

The effects of temperature and the Rht3 dwarfing gene on growth, cell extension, and gibberellin content and responsiveness in the wheat leaf

The effects of low temperature and the Rht3 dwarfing gene onthe dynamics of cell extension in leaf 2 of wheat were examinedin relation to gibberellin (GA) content and GA-responsivenessof the extension zone. Leaf 2 of wild-type (rht3) wheat closelyresembled that of the Rht3 dwarf mutant when seedlings weregrown at 10C. The maximum relative elemental growth rate (REGR)within the extension zone in both genotypes was lower at 10Cthan at 20C, but the position with respect to the leaf basewas unaffected by temperature. The size of the extension zoneand epidermal cell lengths were similar in both genotypes at10C. Growth at 20C, instead of 10C, increased the lengthof the extension zone beyond the point of maximum REGR in thewild type, but not in the Rht3 mutant. Increasing temperatureresulted in longer epidermal cells in the wild type. Treatingwild-type plants at 10C with gibberellic acid (GA₃) also increasedthe length of the extension zone, but the Rht3 mutant was GA-non-responsive.However, the concentrations of endogenous GA₁ and GA₃ remainedsimilar across the extension zone of wild-type plants grownat both temperatures, despite large differences in leaf growthrates. The period of accelerating REGR as cells enter the extensionzone, and the maximum REGR attained, are apparently not affectedby GA. It is proposed that GA functions as a stimulus for continuedcell extension by preventing cell maturation in the region beyondmaximum REGR and that low temperature increases the sensitivitythreshold for GA action. Key words: Cell extension, gibberellin, Rht3 dwarfing gene, temperature, wheat leaf     

Inhibition of flowering and growth in Pharbitis nil by the growth retardant Ancymidol

Flower formation and growth of the short day plant Pharbitisnil, strain "Violet", were inhibited when the growth retardantAncymidol was applied prior to an inductive dark period viacotyledons or roots. Inhibition of flower formation by Ancymidolcould be completely reversed by an application of gibberellinA₃ (GA₃) to the plumule before the inductive dark period. Adose of 0.01 µg GA₃/plant was almost sufficient to restoreflowering, but about a hundred times more GA₃ was required torestore the internode length to that of control. Ancimidol greatlyreduced the endogenous gibberellin content. (Received July 18, 1980; )     

Inhibition of flowering and growth in Pharbitis nil by the growth retardant Ancymidol

Flower formation and growth of the short day plant Pharbitisnil, strain "Violet", were inhibited when the growth retardantAncymidol was applied prior to an inductive dark period viacotyledons or roots. Inhibition of flower formation by Ancymidolcould be completely reversed by an application of gibberellinA₃ (GA₃) to the plumule before the inductive dark period. Adose of 0.01 µg GA₃/plant was almost sufficient to restoreflowering, but about a hundred times more GA₃ was required torestore the internode length to that of control. Ancimidol greatlyreduced the endogenous gibberellin content. (Received July 18, 1980; )     

Identification of Gibberellins in Cotyledonary Embryos of Phaseolus coccineus L.

Gibberellins present in cotyledonary embryos of Phaseolus coccineusL. have been identified by combined gas chromatography-massspectrometry as GA₁, GA₄, GA₅, GA₆; also an unidentified gibberellinwas present. The total amount of gibberellins was estimated by gas chromatographyto be 26.5 µg per g fresh weight; the individual gibberellinscontributed to the total amount as follows: GA₁ 18.4µg,GA₅ 2.6 µg, GA₄ 2.3 µg, GA₆ 1.9 µg, unidentifiedGA 1.3 µg. Data are discussed in relation to previousresults in P. coccineus seed as well as in relation to the embryo-suspensorsystem. (Received December 12, 1985; Accepted July 8, 1985)     

Interaction of Gibberellin A3 and Ancymidol in the Growth and Cell-Wall Extensibility of Dwarf Pea Roots

Effects of ancymidol (Anc) and gibberellin A₃ (GA₃) on rootgrowth, osmotic concentration and cell-wall extensibility ofthe root were investigated in the gibberellin-sensitive cultivarof dwarf pea, Little Marvel. Anc strongly suppressed elongationof both shoots and roots in darkness. Although the elongationof shoots of this dwarf cultivar was severely retarded in thelight, it was repressed still further by Anc. GA₃ promoted elongationof shoots both in the presence and in the absence of Anc, whereasit reversed suppression of root elongation by Anc. The concentrationof GA₃ required for the recovery of root elongation was lowerthan that required for the promotion of shoot elongation. Treatmentwith Anc led to increased thickening of roots with increasednumbers of cells per cross section and lateral expansion ofcells in the cortex. GA₃ had little effect on the osmotic concentration of cell sapobtained from root segments. Anc-treated roots did not respondto acid solutions by elongation, whereas GA₃-treated roots respondednormally to such solutions. Anc suppressed but GA₃ enhancedthe cell-wall extensibility of roots as measured in vivo andin vitro. These results indicate that a low concentration of gibberellinplays a role in normal elongation of roots by maintaining theextensibility of the cell wall in this gibberellin-sensitivedwarf pea. (Received January 17, 1994; Accepted July 15, 1994)     

Effects of Fluorogibberellins on Plant Growth and Gibberellin 3r{beta}-Hydroxylases

3rß-Fluorogibberellin A₉ (3rß-fluoro-GA₉),3rßfluoro-GA₂₀, 3rß-fluorodeoxygibberellinC (3rß-fluoro-DGC) and 13-fluoro-GA₉ were prepared,and their effects on plant growth and gibberellin (GA) 3rß-hydroxyIaseswere examined. 3rß-Fluoro-GA₉ and 3rß-fluoro-GA₂₀promoted the growth of dwarf rice (Oryza sativa L. cv. Tan-ginbozu)seedlings to three times higher than the control seedlings ata dosage of 3 µ plant^–1, and 3rßfluoro-DGCto twice higher at the same dosage. 3rßg-Fluoro-GA₉was active in cucumber (Cucumis sativus L.) hypocotyl assay,its activity being about one-thirtieth as much as that of GA₄.3rß-Fluoro-GAs were active per se in promoting theshoot elongation of rice. 3rß-Fluoro-DGC inhibitedthe 3rß-hydroxylation of [³H₂]GA₉ to [³H]GA₄ by GArß-hydroxylase from bean (Phaseolus vulgaris L.),but 3rß-fluoro-GA₉ and 3rß-fluoro-GA₂₀ didnot show any effects on the enzyme activity. These 3rß-fluoro-GAsalso showed no or only a weak inhibitory effect on the rß-hydroxylasefrom pumpkin (Cucurbita maxima L.). 13-Fluoro-GA₉ promoted growthof rice and cucumber seedlings, and inhibited the 3rß-hydroxylasesfrom both bean and cucumber. 13-Fluoro-GA₉was converted into13-fluoro-GA₄ and 2,3-didehydro-13-fluoro-GA₉, in a cell-freesystem from bean, and conversion of 13-fluoro-GA₉ into 13-fluoro-GA₄was also observed in a cell-free system from pumpkin. Theseresults suggest that 13-fluoro-GA₉ is one of the substratesof GA 3rß-hydroxy-lases, and that 13-fluoro-GA₉ isactive as a result of the conversion to 13-fluoro-GA₄ in riceand cucumber seedlings. (Received October 27, 1997; Accepted March 13, 1998)     

Inoculation with Azospirillum lipoferum Affects Growth and Gibberellin Status of Corn Seedling Roots

Maize (Zea mays L., hybrid Cargill 147) seedlings, grown inaseptic conditions, were inoculated with three strains of Azospirillumlipoferum (Al op 33, Al iaa 320, and ATCC 29708) or culturedin different concentrations of indol-3-acetic acid (IAA) orgibberellin A₃ (GA₃). After 48 h, root length, root surfacearea, root dry weight, and shoot dry weight were measured inall treatments. Gibberellin content was evaluated in selectedroots of control and Azospirillum inoculated seedlings by gaschromatography-mass spectrometry-selected ion monitoring withthe use of deuterated gibberellins as internal standards. Thethree strains of A. lipoferum, IAA (2 ng ml^–1), and GA₃(40 to 400 pg ml^–1) significantly enhanced root growth.Improvement of root hair growth and density was obtained mainlywith A. lipoferum strain Al op 33 and GA₃ 40 pg ml^–1.GA₃ was identified by gas chromatography-mass spectrometry (byboth, full scan and selected ion monitoring) in a free acidfraction from roots of the seedlings inoculated with A. lipoferum.In the roots of the non inoculated seedlings GA₃ was found afterhydrolysis of a fraction expected to contain glucosyl conjugates. (Received April 26, 1993; Accepted September 27, 1993)     

Dormancy in Dioscorea: Generality of gibberellin-induced dormancy in asexual dormant organs

Effects of GA₃ and CCC application on the sprouting of bulbilsor subterranean dormant organs of 10 species in the genus Dioscoreawere observed. Although the efficiency of both chemicals differedby species, in general GA₃ inhibited and CCC promoted the sproutingof the above dormant organs. In some species, however, dilutedGA₃ (0.003–0.3 µM) has a promotive and diluted CCC(3–30 µM) has an inhibitive effect on sprouting. Effects of GA₃ application on shoot elongation were tested onsprouted bulbils. GA₃ promoted elongation when applied directlyto the shoots and inhibited it when applied to the bulbous parts. These results suggest that GA activates two opposing reactions—sprouting-promotingand sprouting-inhibiting—in these organs. The complicatedrelation between GA₃ or CCC concentrations and sprouting wereexplainable by assuming that the two counteractive reactionswere activated by GA in different degrees. ¹ Present address: Department of Biology, Faculty of Science,Yamagata University, Yamagata 990, Japan. (Received June 21, 1976; )     

The role of gibberellins in the growth of floral organs of Pharbitis nil

Evidence that the synthesis of GA₃ is involved in the growthof floral orga'ns of Pharbitis nil is presented. GAs in floralorgans at different developmental stages were surveyed usingTLC followed by the bioassay with two dwarf rice seedlings,‘Tanginbozu’ and ‘Waito-C’. The amountof GAs in the petal and stamen increased rapidly after the petalemerged from calyx, reached a maximum 12 hr before anthesis,then declined markedly thereafter. The GA content in the calyxremained unchanged before and after anthesis, and that in thepistil increased after anthesis. Pharbitis flowers containedat least two active GAs, one of which was probably GA₃, theother appeared to be GA₁₉. GA₃ was detected in relatively largeamounts in both the petal and stamen during their rapid elongation.In the calyx, which showed little increase in fresh weight duringrapid flower growth, GA₉ was the dominant GA. Exogenously suppliedGA₃ promoted elongation of sections in excised young filaments.Sucrose was necessary for definite growth promotion by GA₃.GA₁₉ had little effect on filament elongation, and IAA was ratherinhibitive. (Received July 29, 1972; )     

Identification and Semi-Quantification of Gibberellins from the Pollen and Anthers of Zea mays by Immunoassay and GC/MS

Radioimmunoassays and enzyme-linked immunosorbent assays formethyl esters of gibberellins A₁, A₃, A₄, and A₇ were establishedusing an antiserum specific for GA₁-Me. The antiserum was characterizedby high titer and specificity for such C₁₉-GAs with 3ß-hydroxylgroup as GA₁, GA₃, GA₄ and GA₇. Combination of this antiserumand HPLC enabled us to identify and quantify GA, and GA₄ fromthe pollen of Zea mays with a high degree of reliability. Similarly,identification and quantification of GA₉ and GA₂₀ were alsomade possible by use of an antiserum specific for GA₂₀-Me. Combineduse of immunoassays and GC/MS enabled us to identify nine GAsfrom the pollen and four from the anthers of Zea mays. The identificationof non-13-hydroxylated GAs, such as GA₄ and GA₉, in additionto 13-hydroxylated GAs from the pollen and the anthers suggeststhat the early-non-hydroxylation pathway, as well as the early-13-hydrox-ylationpathway, operates in the male reproductive organs of Zea mays,and that the organ-specific biosynthesis and/or localizationof GAs in Zea mays is similar to that in Oryza saliva. (Received May 7, 1990; Accepted August 20, 1990)