Effect of gibberellic acid on starch content of soybean (Glycine max L.) and its correlation with extension growth

This investigation was undertaken to study the effect of GA₃on extension growth of Glycine max L. and on starch contentof its individual internodes at maturity. The effect on hydrolyticactivity of the extract of different internodes was also studied.GA₃ stimulates the extension growth of stem by increasing theelongation of those internodes which are either in the processof elongation or being differentiated at the time of treatment.Starch content decreases with the position of the internode(from base upwards) on the intact plant. Corresponding internodeshave minimum starch content in 100 ppm GA₃-treated plants andmaximum in the controls. Internodes which show the maximum elongationdue to GA₃ treatment, show the least starch content and alsoshow maximum hydrolytic activity during the period of elongation.It is suggested that enhanced extension growth is brought aboutby enhanced mobilization of reserve food by GA₃. (Received November 21, 1967; )     

The Role of Gibberellins in Early Growth and Development of Sugar Beet

Two gibberellin(GA)-like compounds were found in both rootsand shoots of sugar beet plants using the barley endosperm bioassay.One had chromatographic properties similar to GA₃ and GA₁; theother was highly non-polar, relatively inactive in the endospermassay, and may be a new gibberellin. Presence of the GA_3/1-likecompound was confirmed with the dwarf rice bio-assay. The quantityof this GA was relatively high in the root compared with theshoot at the 3–4 leaf stage when the first supernumerarycambia are being formed in the root. As plants developed throughthe 8–9 leaf stage and the 15–16 leaf stage thequantity of GA per unit fresh weight of material decreased. Application of gibberellic acid (GA₃) to the roots of youngsugar beet plants caused a significant increase in root dryweight shortly after treatment and the rate at which supernumerarycambia were produced was increased. Application of GA₃ to asingle petiole caused a significant increase in both root andshoot dry weight. GA₃ applied to either root or shoot causeda reduction in the rate of leaf formation although total leafarea per plant and shoot dry weight were unaffected. The probablerole of GA-like substances in controlling the growth and developmentof young sugar beet plants is discussed.     

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     

Root Initiation in Cuttings of Pinus radiata Seedlings: II. GROWTH REGULATOR INTERACTIONS

Effects of exogenous growth regulators are related to the histologicalevents in adventitious root initiation in hypocotyls of Pinusradiata D. Don. Indolebutyric acid (IBA) is required both forthe pre-initiative and post-initiative phases in root development.Kinetin has a marked inhibitory effect over the pre-initiativephase, with escape from inhibition following establishment ofmeristemoids. Gibberellic acid (GA₃) has three distinct effectsdepending on time of application. While inhibitory during thepre-initiative phase, it strongly enhances rooting if appliedat a time coincident with the first observable stage of rootinitiation. If applied following establishment of meristemoids,GA₃ inhibits root formation.     

Gibberellin-Induced Suppression of Chloroplast Starch Formation from Exogenous Sucrose in Isolated Epidermis of Light-Grown Cucumber Hypocotyls

The effects of gibberellin A₃(GA₃) on chloroplast starch formationfrom exogenous sucrose in epidermal strips of light-grown cucumber(Cucumis sativus L. cv. Aonagajibai) hypocotyls were studied.Chloroplast starch formation was measured by counting microscopicallythe number of I₂KI stained chloroplasts. In the presence ofsucrose (1–50 mM) and in light, chloroplast starch formationoccurred rapidly for 5 hr and then the rate declined. GA₃ (100µM) simultaneously supplied with sucrose clearly suppressedboth the rate and the degree of starch formation. When the epidermiswas preincubated in the dark with sucrose in the presence orabsence of GA₃ and then post-incubated in light with bufferonly in the presence or absence of GA₃, starch formation wassuppressed to the same degree by GA₃ given either in the pre-or post-incubation period. When the epidermis was preincubatedin the dark with GA₃ alone and then transferred to light forpost-incubation with sucrose alone, GA₃ suppressed the initialrate of starch formation during the post-incubation period.The degradation of chloroplast starch formed in advance fromexogenous sucrose in light was not significantly affected byGA₃ These results are discussed in relation to the mechanismof the GA₃ action and also to the GA₃-induced decrease in theosmotic potential of the cell. (Received February 2, 1982; Accepted May 31, 1982)     

Gibberellin-Induced Changes in Starch Content in Isolated Chloroplasts of Light-Grown Cucumber Hypocotyls

Gibberellin A₃ (GA₃) was found to reduce the starch contentin chloroplasts isolated from light-grown cucumber (cv. Aonagajibai)hypocotyls. Chloroplasts incubated with 50 mM sucrose showedan increase in starch content. The GA₃-induced reduction occurredboth in the presence and absence of exogenous sucrose. GA₃ hadno effect on the level of starch already formed from exogenoussucrose. (Received April 4, 1984; Accepted June 7, 1984)     

Retardation of Leaf Senescence by Ascorbic Acid

Leaf discs of Solatium melongena were floated on various concentrationsof ascorbic acid (AA), gibberellic acid (GA₃), and kinetin inorder to study their effect on senescence. AA was highly effectivein retarding senescence as shown by the arrest of the fall inlevels of chlorophyll, DNA, RNA, and proteins. AA was effectiveat a lower concentration than that of GA₃ or kinetin.     

Peroxidase Ontogeny in a Dwarf Pea Stem as Affected by Gibberellin and Decapitation

The ontogeny of peroxidase activity and isoenzyme pattern wasinvestigated in the stem of dwarf pea plants. Peroxidase activityper unit soluble protein was a given internode is highest inthe youngest growth stage, drops during elongation, remainsconstant upon cessation of growth, and increase at senescence.The lower the internode on the stem the higher is its peroxidaseactivity. These developmental differences are already apparentat the youngest growth stage of the internodes adn increaseduring elongation. Several anodic and five cathodic isoperoxidasesare apparent after starch gel electrophoresis. This patternis constant for all internodes at all growth stages, but therelative importance of particular isoenzymes changes with time. Gibberellic acid (GA₃) treatment causes greatly elongated internodes,decreased soluble protein, and inhibition of the rise in peroxidaseactivity within 4–8 h. Application of GA₃ to young internodesleads to a persistent depression in peroxidase activity, whiletreated older internodes suffer only a temporary depression.GA₃ causes no qualitative changes in the isoenzyme pattern butproduces some quantitative alterations in internodes in whichits influence on peroxidase activity is persistent. Decapitation of untreated and GA₃-treated dwarfs has littleinfluence on internode elongation, causes an increase in peroxidaseactivity, especially in the upper internodes, and alters therelative activity of particular isoenzymes. By contrast, decapitationinhibits elongation of young internodes in genetically tallpea plants.     

Altered Diurnal Leaf Movements in Soybean Seedlings Treated with Triazole Growth Regulators

Treatment of two-week old soybean (Glycine max (L.) Merr. cv.A2) seedlings with 250 µg of either soil-applied paclobutrazolor XE-1019 (also known as S-3307) altered diurnal leaf movementswithin 48 h. Leaf blade and petiole angles of primary leaves,relative to the horizontal, were consistently lower in the triazole-treatedseedlings compared to controls during the daylight hours. Atnight, leaves were completely folded down in both treated andcontrol seedlings, but leaves on treated seedlings reached thefolded down position approximately two hours earlier than controls.A single foliar spray of 6.0 mg-liter^–1 GA₃ counteractedthe triazole effects on leaf blade and petiole angles. (Received February 25, 1987; Accepted July 21, 1987)     

Effect of GA3 and Light on Polysaccharide Levels and Metabolism in Germinating Coffee Seeds

The free sugars and polysaccharides extractable from coffeeseeds during germination in light or darkness increase greatlywhen these seeds are treated with gibberellic acid (GA₃) whichinhibits germination. The major changes are observed in thecontent of free mannose and mannosecontaining polysaccharides.The levels of polysaccharidases are also enhanced by GA₃ treatment.The possible role of these events in the inhibition of coffeeseed germination by GA₃ is discussed.     

Gibberellin-Induced Changes in the Water Absorption, Osmotic Potential and Starch Content of Cucumber Hypocotyls

The effects of GA₃ on the water absorption, osmotic potentialand starch content of light-grown cucumber (cv. Aonagajibai)hypocotyl sections were examined. GA₃ (100µM.) stimulatedfresh weight increase as well as elongation. It had no effecton the dry weight change in the presence, or absence, of 50mM sucrose although dry weight increased significantly in thepresence of sucrose. In the absence of sucrose the weight wasunchanged. The osmotic potential of the epidermal cells of sectionsincubated with GA₃ was lower than that of the control, and thedifference between the two values was larger in young seedlings.When sections were incubated with sucrose, the osmotic potentialgreatly decreased. This decrease was more marked in the presenceof GA₃. GA₃ reduced the starch content of the sections bothin the presence and absence of sucrose. The total amount ofstarch, however, was markedly increased in its presence. Thedegradation of starch formed in advance from exogenous sucrosein light was not accelerated by GA₃. We discuss a possible rolefor gibberellin in cell elongation, based on our results, interms of cell water relations. (Received January 18, 1983; Accepted July 19, 1983)     

The Effect of Gibberellic Acid on Starch Breakdown in Sprouting Tubers of Solanum tuberosum L.

The treatment of potato tubers with 150 µmol dm^–3gibberellic acid (GA₃) stimulated starch breakdown and hexoseaccumulation in tuber tissues and the transfer of dry matterto stems. These effects could not be accounted for by enhancedactivities of starch phosphorylase, amylase and acid invertase.Indeed enzyme activities either declined or remained relativelyconstant as starch degradation and hexose accumulation proceeded.Changes in the rate of starch depletion were related to changesin sink strength and sink type, the onset of tuber initiationin controls causing the rate of starch degradation to exceedthat in GA₃-treated tissues, in which tuberization was inhibited. Solanum tuberosum L., gibberellic acid, starch breakdown     

Effect of Gibberellin on Mature Euonymus europaeus L. Seeds

The release from dormancy of Euonvmus europaeus L embryos bya brief treatment with GA₃ has been studied During 48 h incubationof dormant embryos in GA-free medium, phospholipid levels increasedat first, then declined sharply over the last 6 h When the embryoswere placed in GA₃ medium during this 6 h period levels of totalphospholipids as well as of phosphatidylethanolamine increasedwhilst phosphatidylinositol and phosphatidylcholine declinedslightly Fine structural changes stimulated by a brief GA₃ treatmentwere of different character depending on tissue region (1) ‘destructive’changes occurred in the superficial procortical parenchyma onthe hypocotyl/radicle boundary, involving autolysis and decompartmentationof organelles, (2) ‘positive’ changes occurred inregions close to root and shoot apical meristems, involvingdegradation of protein bodies and their conversion into vacuoles,and the proliferation of various organelles A number of differenceswere noted when the changes in GA₃-treated embryos were comparedwith those induced by low temperature, which also overcomesdormancy The results suggest that germination is accompaniedby different cytological events depending on whether it is inducedby cold or GA₃ The growth of embryos in which dormancy was overcomeby GA3 was due to the activation of the apical root meristemclose to the quiescent centre, whilst in embryos in which germinationwas induced by low temperature, the periphery of hypotocotyl/radicleboundary was the site of activation Euonymus europaeus L, dormant embryo, fine structure, phospholipids, GA₃ and cold treatments     

A Comparison of Petiolar Growth of Isolated Hazel Cotyledons in Response to Stratification and Exogenous GA3

Following stratification seeds of Corylus avellana exhibitedtheir characteristic ability to germinate at 20 °C undermoist conditions. Stratification of the intact fruit also stimulatedelongation of the cotyledonary petiole when isolated cotyledonswere transferred to moist conditions at 20 °C. GA₃ inducedboth of these effects in non-stratified material. ABA substantiallydecreased seed germination and the response of cotyledonarypetioles to stratification and GA₃. CCC² applied to stratifiedor GA₃-pretreated cotyledons did not depress the final percentageof growing petioles. Cotyledons can clearly regulate the development of their petiolesin the absence of the embryonic axis. It is concluded that thereis at least one gibberellin-sensitive site in the cotyledonscapable of initiating petiole development independent of axiscontrol.     

Inhibition of Gibberellic Acid-induced Starch Mobilization by Salicylhydroxamic acid in Avena fatua L. Seed

Inhibition of GA₃-induced endosperm mobilization in Avena fatuaL. by salicylhydroxamic acid (SHAM), a widely used alternativerespiration inhibitor, was studied. SHAM strongly inhibitedthe GA₃-induced release of reducing sugars in the incubationmedium by 3 mm de-embryonated endosperm segments; at 4 mM SHAM,GA₃-induced sugar release was inhibited by 66–79 per cent.Extracts prepared from segments incubated in 0.05 mM GA₃ with2, 5 and 10 mM SHAM showed 30, 53 and 71 per cent lower -amylaseactivity, respectively, compared to the GA₃-alone treatment.Addition of SHAM (0.5–5 mM) during the enzyme assay hadno effect on the activity of -amylase. Thus, the inhibitionof starch mobilization in endosperm by SHAM is due to inhibitionof the production and not the activity of -amylase. The inhibitionof Avena fatua seedling growth by SHAM reported earlier may,in part, be due to its effect on endosperm mobilization. Since (1) Avena fatua seeds have been shown to have little orno SHAM-sensitive respiration, and (2) concentrations of SHAMnecessary for inhibiting endosperm mobilization were significantlyhigher than those generally necessary for inhibiting alternativerespiration, the inhibition of endosperm mobilization by thiscompound does not appear to involve its effect on alternativerespiration. Avena fatua L., wild oat, -amylase, endosperm, gibberellic acid, salicylhydroxamic acid, seed     

Auxin-gibberellin relationships in. their effects on hypocotyl elongation of light-grown cucumber seedlings IV. Inhibition of IAA-induced elongation by N,N'-dicyclohexylcarbodiimide and its reversal by gibberellin A3

IAA-induced elongation and control growth of light-grown cucumberhypocotyl sections were markedly inhibited by DCCD, an inhibitorof membrane-bound ATPases. The concentration effective for inducingmarked inhibition was more than 10^–5 M. At 10^–5M DCCD, there was an apparent antagonism between IAA and DCCD.At 5 x 10^–5 M DCCD, the inhibition was partially recoveredby 10^–4 M of IAA. The results might indicate a close associationof the auxin action with membrane-bound ATPases. The DCCD inhibitionwas so strong that treatment with 10^–4 M DCCD for about5 min significantly suppressed further growth and longer incubationkilled the sections. In contrast, DCCD had not inhibitory effecton both control growth and IAA-induced elongation if GA₃ waspresent simultaneously. DCCD treatment followed by GA₃ treatmentstill resulted in the inhibition, suggesting that the inhibitionwas not reversible. In order to obtain reversal of DCCD inhibitionby GA₃ both compounds must be present at the same time. TheGA₃ effect is discussed in connection with the mechanism ofDCCD action on membrane-bound ATPases. (Received October 6, 1975; )     

An Analysis of the Effects of Gibberellic Acid on Tomato Leaf Growth

The effects of four consecutive daily sprays of gibberellicacid (GA₃) on the growth of leaves of young tomato plants cv.Potentate were studied. Total leaf weight and area were increasedby GA₃. The percentage changes were larger in the younger leavesthan in the older but the absolute increases of the middlleleaves accounted for most of the total response. Chlorophyllcontent, both total and per unit weight, was reduced by GA inthe older leaves and increased in the younger; on an area basisit was reduced in all but the youngest leaves. Palisade cell length and palisade cell number per unit sectionlength were reduced by GA₃ in the oldest leaves and increasedin the youngest. There were larger intercellular spaces in bothmesophyll layers and a larger transectional area of the mid-ribsof the oldest and two youngest leaves in GA₃ plants. The ‘surfaceareas’ of epidermal cells were also increased by GA₃ treatment.Leaf fresh weight per unit area was only a true index of laminathickness in the two oldest leaves.     

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; )     

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)     

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.