Auxin-gibberellin relationships in their effects on hypocotyl elongation of light-grown cucumber seedlings VI. Promotive and inhibitory effects of kinetin

The interaction of kinetin with IAA and GA₃ on the elongationof hypocotyl sections of Cucumis sativus L. cv. National Picklingwas studied. Kinetin in the concentration range of 10^–7M to 10^–4 M markedly inhibited IAA-induced elongation,while in a lower range from 10^–10 M to 10^–8 M, itsynergistically enhanced IAA-induced elongation. Kinetin alonein this range had no effect. A 5-to 15-min pulse treatment seemsenough to induce the maximum effect for both inhibition andpromotion. Since the magnitude of the maximum inhibition dependedon the concentration and not on the duration of treatment, thereaction in the cell caused by kinetin seemed to be completedwithin a short period. Washing of the sections with distilledwater after kinetin treatment (30 min) did not significantlyeliminate the kinetin effect. This probably indicates that thebinding of kinetin molecules to a supposed acceptor is not reversible.Interaction of kinetin with GA₃ in their pretreatment effectson IAA-induced elongation shows that in the inhibitory concentrationrange, the kinetin effect was partly overcome by GA₃, and thatin the promotive range, the magnitude of the enhancement wasdetermined by kinetin regardless of the presence of GA₃. Theeffect of kinetin seems to dominate over that of GA₃ indicatingthat the modes of their pretreatment effects differ from oneanother. (Received June 24, 1977; )     

Auxin-gibberellin relationships in their effects on hypocotyl elongation of light-grown cucumber seedlings II. Effect of GA3-pretreatment on IAA-induced elongation

IAA-induced growth of light-grown cucumber hypocotyl sectionsis markedly enhanced by GA₃-pretreatment of the sections; thereis a distinct synergism between IAA and GA₃. Water pretreatmentalso enhances IAA-induced growth. On the other hand, IAA-pretreatedsections showed practically no further growth in response topost treatment with GA₃. The enhancing effect of GA₃ is obtainedwith only 30 min pretreatment, the maximum effect occuring with2 hr pretreatment. Pretreatment longer than 8 hr is less effective.This enhancing effect of GA₃ can be observed soon after posttreatment with IAA. The response of GA₃-pretreated sectionsto IAA is greater in pretreatment with higher concentrationsof GA₃, and higher degrees of synergism between IAA and GA₃are obtained at IAA concentrations less than 10^-4 M. This synergisticinteraction between GA₃ and IAA is more marked in aged hypocotylsections than in young sections. From these results we concludedthat gibberellin sensitizes hypocotyl cells to the subsequenteffect of auxin on cell elongation. (Received October 6, 1973; )     

Biological activities of rishitin, an antifungal compound isolated from diseased potato tubers, and its derivatives

Rishitin, a norsesquiterpene alcohol, found in infected, resistantpotato-tuber tissue completely inhibited zoospore germinationand germtube elongation of Phytophthora infestans (MONT.) DEBARY at 10^–3M. There was little difference in sensitivityto rishitin among races of Phytophthora infestans. IAA-inducedelongation of Avcna coleoptile sections and GA₃-induced elongationof wheat leaf sections were also inhibited by rishitin. Theinhibition of IAA-induced elongation of Avena coleoptiles wasrelieved to some extent by increasing IAA concentration. However,little relief of the inhibition of GA₃-induced elongation ofwheat leaf sections was obtained by increasing GA₃ concentration.No plant injury was observed at this concentration of rishitin(10^–3M). Examination of a series of rishitin derivatives indicated thatthe hydroxyl group at C-3 is indispensable for antifungal activity.This activity was intensified by saturating the double bondbetween the rings of rishitin and/or that of the isopropenylgroup at C-7, though activity decreased when oxygenated functionalgroups were introduced into the side chain. Aromatization of the A ring did not lower biological activities.The antifungal activities of most rishitin derivatives almostparalleled their activities as plant growth retardants. However,some compounds without antifungal activity were active as growthretardants. ¹Studies on the phytoalexins (5). (Received August 14, 1968; )     

Auxin-gibberellin relationships in their effects on hypocotyl elongation of light-grown cucumber seedlings V. Reversal of N, N'-dicyclohexylcarbodiimide-induced inhibition of section growth by some adenine nucleotides and gibberellin A3

DCCD, an inhibitor of membrane-bound ATPases, markedly inhibitedboth the endogenous and IAA-induced growth of cucumber hypocotylsections. The inhibition was negated by the simultaneous applicationof ADP, ATP and 3',5'-cyclic AMP. The effect of these nucleotideswas similar to that of GA₃. Adenine, adenosine, AMP, 2',3'-cyclicAMP, CTP, GTP, ITP and UTP were all ineffective. (Received April 26, 1976; )     

Abscisic Acid and Apical Dominance in Phaseolus coccineus L. The Role of Tissue Age

Abscisic acid (ABA) applied to the decapitated second internodeof runner bean plants enhanced outgrowth of lateral buds onlywhen internode stumps were no longer elongating. Applied toelongating internodes of slightly younger plants, ABA causesinhibition of bud outgrowth. Together with 10^–4 M indol-3-ylacetic acid (IAA), ABA stimulated internode elongation and interactedadditively in the inhibition of bud outgrowth. A mixture of10^–5 M ABA and 10^–6 M gibberellic acid (GA₃ ) causedsimilar effects on internode growth as IAA + ABA, but was mutuallyantagonistic in effect on growth of the lateral buds. Abscisic acid, apical dominance, gibberellic acid, indol-3yl acetic acid, Phaseolus coccineus, bean     

The Effect of Selected Growth-Promoting and Growth-Inhibiting Substances on the Extension of Segments of Etiolated Tomato Seedling Hypocotyls

The effects of a number of growth-promoting and growth-inhibitingsubstances, including two fungal toxins, were studied on theextension of segments of etiolated tomato seedling hypocotyls.The bioassay was sensitive to small quantities of NaF, coumarinand ₂, ₄-DNP and inhibition was observed at all concentrations.₂, ₄-DNP or Iodoacetate stimulated growth at concentrationsbetween 1? 10^–4 and 5 ? 10^–6M. or 1 ? 10^–6and 1 ? 10^–7M. respectively. Inhibitor experiments inbuffered nutrient solution were approximately 10 per cent. moresensitive than those in deionized water. By means of paper partition chromatography small quantitiesof two fungal toxins, fusaric and alternaric acid were chromatographedand bioassayed. The effect of fussric acid (5, n-butyI picolinicacid) on hypocoty1 growth was detected at concentrations aslow as 1 ? 10^–5M. Experiments with recongnized growth-promoting substances showedthat Kinetin inhibited growth at concentrations up to 1 ?10^–8M.in both light and dark. IAA inhibited growth up to 1 ? 10^–6M.At 1 ? 10^–7 and 1 ? 10^–8 only small increases occurredwith IAA and the effect of light was negligible. Gibberellicacid (GA₂)stimulated growth at concentrations from 10^–3to 10^–7M. and significant increases up to 17 per cent.were recorded in the light. Since the light induced inhibitionwas only partly restored, the existence of some other naturallight sensitive growth substance is suggested. The value ofthe bioassay as a method for estimating natural growth-inhibitingand growth-promoting substances is discussed.     

Biological activity of phyllosinol, a phytotoxic compound isolated from a culture filtrate of Phyllosticta sp.

1. Phyllosinol is a phytotoxic metabolite of Phyllosticta sp. Thissubstance at 100 µg/ml produced dark grey necrotic lesionson the leaf of red clover. Sensitivities of various plant speciesto phyllosinol differed both quantitatively and qualitatively.
2. Phyllosinol reduced root growth in rice seedlings by 60% at10^–4 M, whereas stimulation of root elongation occurredat a concentration range from 10^–9 to 10^–5 M.
3. Phyllosinolat 2.5x10^–4M promoted adventitious root formationin epicotylsof Azukia cuttings by about 100%. Promotion waspartly reducedby simultaneous application of cysteine.
4. IAA-induced elongationof isolated Avena coleoptile sectionswas inhibited by phyllosinolat a concentration range from 10^–5to 10^–3M.
5. Sulfhydrylcompounds, i.e. cysteine and glutathione relievedinhibitioncaused by phyllosinol in IAA-induced elongation ofAvena coleoptilesections.
6. GA₃-induced elongation of wheat leaf sections wasslightly inhibitedby phyllosinol at 10^–4M.
7. Phyllosinolalso has antibiotic activity. Among the organismstested, Phycomycetesand Gram-negative bacteria appeared mostsusceptible to phyllosinol.

(Received April 21, 1970; )     

Involvement of cellulose synthesis in actions of gibberellin and kinetin on cell expansion. Gibberellin-coumarin and kinetin-coumarin interactions on stem elongation

In azuki bean (Azukia angularis = Vignia angularis) epicotylsections, 5 ? 10^–4 M coumarin inhibited the incorporationof radioactivity from [U^–14C]glucose into the cellulosefraction by 35% in the absence of indole-3-acetic acid (IAA)and by 40% in the presence of 1 ? 10^–4 M IAA. There wasno inhibitory effect on the incorporation of radioactivity intothe other fractions. Coumarin at 5 ? 10^–4 M reversed thepromoting effect of 1 ? 10^–5 M gibberellin A₃ (GA) andthe inhibitory effect of 1 ? 10^–5 M kinetin on IAA-inducedelongation of sections with no significant effects on IAA-inducedelongation. Neither GA nor kinetin had any appreciable effectson cellulose synthesis. No inhibition of cellulose syntheiswas observed with 1 ? 10^–3 M colchichine, which has beenreported to have effects similar to those of coumarin on GA-or kinetin-affected stem elongation. Coumarin at 5 ? 10^–4M was ineffectual in breaking up wall microtubules, while adisrupting effect on wall microtubules was clearly demonstratedwith 3 ? 10^–4M colchicine. From these results, the possible involvement of cellulose synthesisin cell expansion controlled by GA or kinetin was suggested. (Received August 3, 1973; )     

Effects of Auxin and Gibberellin on Elongation of Young Hyphae in Neurospora crassa

IAA, 2,4-D and GA₃ promoted the elongation of young hyphae inNeurospora crassa at the optimum concentrations of 10^–6,10^–6 and 10^–4 M, respectively. The effects of IAAand GA₃ were additive. (Received June 17, 1983; Accepted December 22, 1983)     

Auxin-gibberellin relationships in their effects on hypocotyl elongation of light-grown cucumber seedlings. Responses of sections to auxin, gibberellin and sucrose

The sensitivity of light-grown cucumber hypocotyl sections toIAA and GA₃ depends on the degree of aging of the tissue. Agreater response to GA₃ was obtained with young tissue, whilethat to IAA was obtained with relatively old tissue. The responseto IAA reached a maximum at about 15 hr of incubation; the youngerthe tissue the earlier the time of maximum response. The responseto GA₃ continued for more than 70 hr with a constant growthrate. Very young tissue started to respond to GA₃ without lagtime; the older the tissue the later the start of the response. Sucrose (2%) inhibited IAA-induced elongation, while there wasa distinct synergism between GA₃ and sucrose. The promotiveeffect of sucrose on GA₃-induced elongation was also obtainedwhen sections were pretreated with sucrose, then transferredto GA₃. Mannitol (1%) strongly inhibited IAA-induced elongation,but not GA₃-induced elongation. (Received December 6, 1972; )     

Effects of Auxin and Gibberellin on Conidial Germination and Elongation of Young Hyphae in Gibberella fujikuroi and Penicillium notatum

In Gibberella fujikuroi and Penicillium notatum, IAA, 2,4-Dand GA₃ promoted conidial germination and the elongation ofyoung hyphae. The promotive effects of IAA and GA₃ were additive.In both fungi, the concentrations of endogenous auxin and gibberellinin the culture media were 10^–10 to 610^–12M. (Received April 27, 1985; Accepted August 12, 1985)     

Inhibition of Gibberellic Acid-Induced Elongation-Growth of Pea Epicotyls by Xyloglucan Oligosaccharides

The biological activity of a cell wall-derived xyloglucan nonasaccharide(XG9) was investigated using a bioassay with entire pea epicotyls(Pisum sativum cv. Progress). The xyloglucan fragment was foundto inhibit gibberellic acid-induced elongation of etiolatedpea epicotyls with maximum inhibition at concentrations rangingfrom 10^–11 to 10^–9M. Growth of etiolated epicotylsin the absence of exogenously applied GA₃ was also inhibitedby XG9 in the same concentration range. A cell wall-derivedheptasaccharide (XG7) lacking the fucosyl-galactosyl-side chainshowed no inhibitory effect in the pea epicotyl bioassay withand without exogenous GA₃. Furthermore, the biological activityof a synthetic pentasaccharide (XG5), containing the fucosylgalactosyl-sidechain which is necessary for the biological activity was investigatedin the same bioassay. Compared to XG9 the pentasaccharide hada similar inhibitory activity on GA₃-promoted elongation aswell as on the endogenous growth in the absence of exogenouslyapplied GA₃, but did not exhibit a distinct concentration optimum. Key words: Elongation-growth, gibberellic acid (GA₃), oligosaccharides, pea, XG9     

Auxin-gibberellin relationships in their effects on hypocotyl elongation of light-grown cucumber seedlings III. Gibberellin specificity in its enhancing effect on IAA-induced elongation

Pretreatment effects of different gibberellins, helminthosporicacid, cyclic AMP and Kinetin on subsequent IAA-induced elongationwere tested in cucumber hypocotyl sections. Gibberellin A₇ wasmore active than GA₃, while gibberellin A₃ was almost inactive.Both helminthosporic acid and cyclic AMP mimicked GA₃-action,though the degree of their activity was less. Kinetin pretreatmentresulted in marked inhibition of IAA-induced elongation. Thepretreatment effect of GA₃ was also reflected in a greater responceof the sections to synthetic auxins. (Received October 6, 1973; )     

Effect of {alpha}-Tomatine on the Response of Wheat Coleoptile Segments to Exogenous Indole-3-acetic Acid

A concentration of 10^–5 M tomatine had no effect on leakagefrom, or elongation of, wheat coleoptile segments, but consistentlyreduced IAA-enhanced extension growth by c. 50 per cent. Therewas no evidence of chemical interaction between the alkaloidand the auxin in solution, and IAA action was not affected bypre-treatment for up to 3 h with 10^–5 M tomatine. Studieswith [2-¹⁴C]IAA revealed that 10^–5 M tomatine did notinhibit uptake of auxin into segments. The effect of pre-treatingsegments for up to 3 h with IAA could be virtually nullifiedby 10^–5 M tomatine, as could also IAA-induced changesin properties of coleoptile cell walls. Results are discussedin relation to the ability of tomatine to disrupt membrane functionand to current hypotheses implicating membranes in the primaryaction of auxin.     

Effect of Xyloglucan Nonasaccharide on Cell Elongation Induced by 2,4-Dichlorophenoxyacetic Acid and Indole-3-acetic Acid

Xyloglucan nonasaccharide (XG9) is recognized as an inhibitorof 2,4-D-induced long-term growth of segments of pea stems.In the presence of 10^–5 M 2,4-D, inhibition by 10^–9M XG9 of elongation of third internode segments of pea seedlingswas detected within 2 h after the start of incubation, in someexperiments. Analysis by double-reciprocal (Lineweaver-Burk)plots of elongation in the presence of various concentrationsof 2,4-D, with or without XG9, gave parallel lines, indicatingthat XG9 inhibited 2,4-D-induced elongation in an uncompetitivemanner. XG9 did not influence the 2,4-D-induced cell wall loosening.Thus, XG9 does not fulfill the proposed definition of an "antiauxin". XG9 at 10^–11 to 10^–6 M did not influence IAA-inducedelongation of segments from pea third internodes, azuki beanepicotyls, cucumber hypocotyls, or oat coleoptiles. Inhibitionof IAA-induced elongation by XG9 was not observed even whenthe segments from pea or azuki bean were abraded. Furthermore,fucosyl-lactose at 10^–11 to 10^–4 M did not affectthe IAA-induced elongation of segments of pea internodes orof azuki bean epicotyls. XG9 may be incapable of inhibitingthe IAA-induced cell elongation (especially in oat) or, alternatively,the endogenous levels of XG9 may be so high that exogenouslyapplied XG9 has no inhibitory effect on IAA-induced elongation. (Received February 28, 1991; Accepted May 25, 1991)     

Factors Influencing Alanine Aminotransferase Activity in Leaves of Lolium temulentumL.: II. EFFECTS OF GROWTH REGULATORS AND PROTEIN BIOSYNTHESIS INHIBITORS

Effects of kinetin (K), gibberellin A₃ (GA₃), and 2-(chloroethyl)-trimethylammoniumchloride (CCC) on levels of alanine aminotransferase (GPT) andrates of protein synthesis were studied with both intact plantsand isolated leaf segments of Lolium temulentum L. In intactplants CCC stimulated and CA₃ reduced GPT activity, the effectsbsing much greater in 8.h than in 16-h photoporiods. CCC showedmaximum stimulatory effects at 10^–2 M and K at 5 x 10⁵M. No effect of GA₃ could be demonstrated with concentrationsup to 10^–4M. Both K and CCC retarded GPT decline in leafsections, the latter without associated effects upon pigmentbreakdown. Cycloheximide was highly effective in reducing proteinsynthesis in leaf sections. A close correlation between rateof protein synthesis and GPT activity was found over an inhibitorconcentration range from 10^–6 to 10^–4 M. The resultsare discussed in terms of possible methods of in vivo regulationof GPT activity.     

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     

Gibberellin-colchicine interaction in elongation of azuki bean epicotyl sections

In azuki bean (Azukia angularis = Vigna angularis) epicotylsections, gibberellin A₃ (GA₃) enhanced the growth promotingeffect of indoleacetic acid (IAA), but showed no growth effectwhen applied alone. Sections showed practically no cell division.The promoting effect of GA₃ on section growth seems to be dueto its promoting effect on cell elongation. The diameters of sections treated with IAA increased, but thediameters of sections treated with GA₃ together with IAA remainedconstant. GA₃ seems to suppress cell expansion in a directiontransverse to the cell axis. Colchicine at a concentration with no inhibiting effect on IAA-inducedelongation almost completely reversed the effect of GA₃ On the basis of these results, the participation of wall microtubulesin GA₃-induced elongation is discussed. (Received October 22, 1971; )     

Effects of Gibberellic Acid and Naphthaleneacetic Acid on Petiole Senescence and Subtended Peduncle Growth of Cyclamen persicum Mill

Removal of the blade from the leaf subtending the first flowerbud on Cyclamen persicum ‘Swan Lake’ plants causedthe petiole of that leaf to senesce, but had no effect on thegrowth of the flower peduncle in the debladed petiole's axil.A 10 mg NAA l^–1 application generally had no effect onpetiole senescence, peduncle elongation or flowering date whenapplied to the cut end of the petiole after blade removal. A25 mg GA₃ l^–1 application or a combination of 25 mg GA₃l^–1 application or a combination of 25 mg GA₃ l^–1plus 10 mg NAA l^–1 delayed petiole senescence and enhancedpeduncle elongation and subsequent flowering. No treatment significantlyaltered peduncle length at the time of flowering. Cyclamen persicum Mill, ‘Swan Lake’, tissue receptivity, flowering, GA₃, NAA     

Roles of Ethylene and Indol-3yl-acetic Acid in Petiole Epinasty in Helianthus annuus and the Modifying Influence of Gibberellic Acid

The effect of 12 h exposure to ethylene upon epinastic curvatureand elongation of a 5-cm segment in the attached petiole ofHelianthus annuus has been investigated in either normal orGA₂-treated plants. Curvature of segments occurred rapidly inthe first. 6 h during exposure of normal plants to either 1.0or 40.0 parts/10⁶ ethylene, and continued slowly from 6 to 12h. After the ethylene treatment, recovery from the induced curvaturewas completed in 12 h. In 0.2 parts/10⁶ ethylene, recovery fromthe epinastic curvature began during the second half of thetreatment period. Pre-treatment of plants with 60 µg GA₃,did not change the epinastic response to 40.0 parts/10⁶ ethylene.In 10.0 parts/10⁶ ethylene, recovery commenced towards the endof the treatment period, while in 1.0 parts/10⁶ the onset ofepinasty was delayed by about 6 h. In 0.2 parts/10⁶ ethylenethe epinastic response was slight. Ethylene accelerated elongation in the upper half of the petiolesegment. This response was completed within 12 h in all concentrationsand in both normal and GA₃-treated plants. The mean elongationrate in the lower half was depressed from 4.6 to 1.0 mm 24h^–1in 40.0 parts/10⁶ but immediately afterwards it rose to 14.2mm 24 h^–1. A similar response occurred in 1.0 parts/10⁶.In contrast, the elongation of the lower half of the petiolesegment was stimulated by 0.2 parts/10⁶ ethylene. GA₂-treatedplants showed an initial depression of elongation in the lowerhalf in 10.0 or 40.0 parts/10⁶ ethylene, but in the second partof the treatment period the elongation rate recovered to thatof the control segments. Both 0.2 and 1.0 parts/10⁶ ethylenestimulated elongation growth in the lower half of segments inGA₂-treated plants. Removal of the leaf lamina inhibited segment elongation, butdid not affect the growth response of the upper half to 40.0parts/10⁶ ethylene. In contrast the lower half of the segmentno longer showed the usual growth responses to 40.0 parts/10⁶ethylene, although these were partially retained when 10µgof IAA was applied to the cut end of the petiole.