Factors Influencing the Distribution of Growth Between Stem and Axillary Buds in Decapitated Bean Plants

Phaseolus multiflorus plants at three stages of developmentwere decapitated either immediately below the apical bud orlower down at a point 1 cm above the insertion of the primaryleaves. Growth regulators in lanolin were applied to the cutstem surface. IAA always inhibited axillary bud elongation anddry-matter accumulation, and enhanced internode dry weight butnot elongation. GA₃ applied below the apical bud greatly increasedinternode elongation and dry weight, but simultaneously reducedbud elongation and dry-weight increase. Application of GA₃ 1cm above the buds had no effect on bud elongation in the youngestplants, but enhanced their elongation in the two older groups.IAA always antagonized GA₃-enhancement of internode extensiongrowth, whereas its effects on GA₃-enhanced dry-matter accumulationdepended on the stage of internode development. Bud elongationwas greater in plants treated with GA₃+IAA than in plants treatedonly with IAA, except in the youngest plants decapitated immediatelybelow the apical bud, where GA₃ caused a slight increase inIAA-induced bud inhibition. GA₃ increased inhibition of buddry weight by IAA in the two youngest groups of plants, butslightly reduced it in the oldest plants. No simple compensatorygrowth relationship existed between internode and buds. It wasconcluded that, (1) auxin appears to be the principal growthhormone concerned in correlative inhibition, and (2) availabilityof gibberellin to internode and buds is of importance as a modifyingfactor in auxin-regulated apical dominance by virtue of itslocal effects on growth in the internode and in the buds.     

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     

Mode of Action of IAA and GA3 on Root and Shoot Growth of Epiphyllous Buds of Bryophyllum tubiflorum

Darkness and GA₃ stimulate the elongation of the first internodebut inhibit the production of roots while IAA inhibits internodalelongation but promotes the production of roots on epiphyllousbuds of Bryophylhum tubiflorum. Cycloheximide inhibits both,implicating the synthesis of proteins in the growth of bothroot and shoot. Even pre-treatment of buds with cycloheximidefor 4 h inhibits rooting as well as internodal elongation whenthese are subsequently transferred to IAA or GA₃. On the otherhand, pre-treatment with IAA or GA₃ even for 8 h does not alleviatethe inhibitory effect of cycloheximide suggesting that thereis a lag period between the application of these regulatorsand the synthesis of proteins caused by them.     

Effects of external ABA,GA<Subscript>3</Subscript> and NAA on the tiller bud outgrowth of rice is related to changes in endogenous hormones

Hormones play an important role in regulating the growth of rice tiller buds. However, little is known about the hormonal changes that occur during tiller bud growth and the mechanism of hormonal regulation of tiller bud growth. Here, two rice cultivars, Yangdao 6 (Indica) and Nanjing 44 (Japonica), were used to investigate the changes in plant hormones during tiller bud growth and the mechanism that underlies the hormonal regulation of tiller bud growth. In the present study, panicles were removed after heading to stimulate the growth of dormant tiller buds located at the elongated upper internodes. At the same time, external abscisic acid (ABA), gibberellic acid (GA₃) and α-naphthalene acetic acid (NAA) were applied. The results demonstrated that auxin and cytokinin (CTK) play important and different roles in the regulation of tiller bud growth. Auxin in the nodes inhibits tiller bud growth, while CTK is transferred to the tiller buds to promote growth. The inhibitory effects of GA₃ and NAA on tiller bud growth are mainly due to the control of the indole-3-acetic acid (IAA) or CTK contents in plants. As opposed to auxin and CTK, the ABA contents in nodes and tiller buds remained unchanged before tiller bud growth after panicle removal. Meanwhile, external ABA application only slightly slowed the growth of the tiller buds, suggesting that ABA may not be a key regulator of tiller bud growth. These results indicate that auxin, CTK and ABA together likely play roles in the regulation of tiller bud growth.     

Interaction between Hormones, Light, and Nutrition on Extension of Lateral Buds in Phaseolus vulgaris L.

Gibberellic acid (GA₃), kinetin, and indol-3yl-acetic acid (IAA)contained in lanolin were applied in various combinations andconcentrations to decapitated stems and petioles and to budsof Phaseolus vulgaris L. GA₃ applied alone usually promotedgrowth of main stems and laterals but this was by no means consistentand occasionally it acted in the opposite way. IAA applied alonereduced lateral bud extension slightly, but not consistently;however, when applied with GA₃ or GA₃ plus kinetin, it oftenmarkedly inhibited the promotion caused by these compounds.On occasions, however, GA₃ and IAA acted synergistically topromote and sometimes to inhibit lateral shoot growth. Kinetinalone showed few significant effects on lateral shoot growthbut applied with GA₃ it often dramatically increased GA₃-inducedgrowth of main stems and laterals. The diversity of these results,which parallels that found in the literature, was shown to bepartly dependent on the point of hormone application and ageof the plant or bud, on concentration of hormone and on lightintensity or nutrition. However, no meaningful relationshipswere found and it is concluded that growth of laterals and mainstems is dependent on a hormone balance which can be criticallymodified by a wide range of internal and external factors thenature of which is still to be determined.     

Dwarfism Caused by Floral-Bud Removal in Petunia and its Reversal by Gibberellin

The effect of floral-bud removal at different stages of developmenton the plant height and on the total number of buds of Petuniawas studied. Continuous removal of all the floral buds 2 d beforeanthesis caused a marked decrease in plant height and also increasedthe total number of floral buds formed thereafter. At otherstages of floral bud development, bud removal had a lesser effecton both phenomena. Moreover, the plants did not respond to budremoval at anthesis. GA₃ at 25 ppm applied to plants from which the buds had beenremoved, promoted stem elongation. The most pronounced effectwas on plants from which the buds were removed 2 d before anthesis,but it had no effect on plants from which the buds were removedat anthesis stage. The possible involvement of endogenous growth hormones in theresponse of Petunia plants to floral-bud removal and to applicationof GA₃ is discussed. Bud removal, bud number, dwarfness, GA₃, Petunia, plant height     

枣花芽分化过程中营养物质和内源激素含量及抗氧化酶活性变化研究

以新疆主栽品种灰枣和骏枣的花芽为材料,测定不同分化时期花芽的可溶性糖、还原糖、淀粉、可溶性蛋白含量,SOD、POD、PPO、CAT活性以及内源GA3、IAA、ABA、ZT水平的变化,并分析它们与花芽分化的关系,为枣花芽分化调控提供理论参考.结果表明:(1)灰枣和骏枣花芽可溶性糖、还原糖和淀粉含量在花芽分化过程的变化趋势...     

Effects of Plant Growth Regulators and Nutrient Supply on Tiller Bud Outgrowth in Barley (Hordeum distichum L.)

Seedlings of spring barley were raised in 100 and 20% nutrientsolution and treated with a foliar application of Terpal, Cerone,TIBA, GA₃ or BAP. The growth of individual tiller buds and tillers,the main shoot and the root system was recorded over the following15 d. Terpal and Cerone stimulated tiller bud elongation within5 d at both nutrient levels and after 15 d the number of emergedtillers was increased at the higher nutrient level. Terpal characteristicallypromoted the growth of secondary tiller buds whereas Ceronepromoted the emergence of the coleoptile tiller; both thesePGRs also retarded the development of the main shoot. TIBA increasedthe number of elongating tiller buds but this did not resultin greater tillering. GA₃ reduced the number of elongating tillerbuds and restricted their growth, especially in the high nutrientregime; this was accompanied by an increase in main shoot elongation.The growth and development of tiller buds was reduced by BAPand the number of emerged tillers was reduced at 15 d in bothnutrient levels; main shoot dry weight and root elongation werealso reduced. The results are considered in relation to theoverall influence of hormonal factors and mineral supply ontiller bud outgrowth. Hordeum distichum, spring barley, tiller bud outgrowth, plant growth regulators, Terpal, Cerone, GA₃, BAP, nutrient supply, apical dominance, TIBA     

Specificity of Gibberellin and Sucrose-promoted Flower Bud Growth in Gladiolus

A critical stage in flower bud growth in the spike of Gladioluswhich is initiated by gibberellic acid (GA₃) and sustained bysucrose has been identified. This corresponds to the stage atwhich separation of the outer bract occurs. In buds at differentdevelopmental stages isolated and held in water, it is the samebud stage that first shows increased growth. Buds not inducedby light were shown to respond more significantly to GA₃ andsucrose than those induced by light. Since the separation ofthe outer bract results in light-induced amylase productionand starch hydrolysis leading to petal growth, it is proposedthat growth promotion by GA₃ is related to light-induced petalgrowth at this specific stage. flower bud growth, Gladiolus natalensis, gibberellic acid, sucrose     

In Vitro Floral Development of Oilseed Rape (Brassica napus L.): The Effects of pH and Plant Growth Regulators

The effects of various plant growth regulators and that of pHon the in vitro growth and development of young inflorescencesof Brassica napus L. cv. Westar were examined. A cytokinin wasrequired for normal maturation of floral buds, including thecompletion of microsporogenesis, and it stimulated the initiationof additional buds on the inflorescence axis. Benzylaminopurine(BAP) was the most effective of the cytokinins tested. Gibberellicacid (GA₃) and naphthaleneacetic acid (NAA) alone were ineffective.In combination with BAP, both reduced the positive influenceof the cytokinin but GA₃ was more inhibitory than NAA. At alow initial pH (3.9–4.6), the percentage of cultures whichproduced normal buds was significantly higher, especially inthe presence of 10^-7 M or 5 ? 10^-7 M BAP, in comparison to cultureswith a pH of 5.3-6.0, the standard range for plant tissue culture.     

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; )     

Influence of Several Growth Regulators and Amino Acids on in vitro Organogenesis of Torenia fournieri Lind.

The effects of several growth regulators and amino acids onin vitro organogenesis of Torenia fournieri Lind. were determinedusing internodal segments. Treatment with 2,4-D¹ resulted innodular callus formation, while NAA and IAA induced roots constantlybut much less frequently shoot buds. Individually BA, zeatin,and 4-PU induced bud formation, but these shoot buds did notdevelop further. Formation of buds by cytokinin was influencedby a simultaneous application of NAA or 2,4-D, but not of IAA,its degree being reduced when BA was simultaneously appliedwith NAA or 2,4-D. When zeatin or kinetin was added with NAA,numerous roots were induced. The effects of various L-amino acids on in vitro organogenesiswere also investigated using the defined medium in which KNO₃was a principal source of nitrogen. The formation of buds wasconsiderably stimulated by alanine and asparagine, and slightlyby glutamic acid in the medium containing both NAA and BA, inwhich bud formation was easily induced. On the other hand, allamino acids except for glutamic acid and aspartic acid inhibitedroom formation in this medium. Root formation was greatly stimulated by proline, alanine, glutamine,glutamic acid, and aspartic acid, and slightly by arginine andtryptophan in the medium containing NAA but no BA. Glutamicacid and aspartic acid also enhanced bud formation in this medium.     

Effect of Gibberellic Acid, 2,3,5-Triiodobenzoic Acid and Indole Acetic Acid on Growth and Development of Impatiens balsamina during Different Photoperiods

This paper deals with the effect of 100 mg/1 each of GA₃ TIBA and IAA singly and in combination with each other on stem elongation, development of lateral branches and floral bud initiation in Impatiens balsamina plants exposed to 8-, 16- and 24-h photoperiods. GA₃ enhances stem elongation, the enhancing effect decreasing with IAA as well as with TIBA during 8-h but increasing during 16- and 24-h photoperiods. It decreases the number of lateral branches, the decrease being greatest during 16-, less during 8- and the least during 24-h photoperiods. The time taken for floral buds to initiate with and length of branches during 16-h photoperiods. During 8-h photoperiods, IAA delays the initiation of floral buds, while GA₃ hastens it when used together with TIBA or IAA or both. GA₃ increases the number of floral buds on the main axis but decreases it on lateral branches, while TIBA decreases the number on the main axis but increases it on lateral branches. IAA reduces the number of floral buds on the main axis only when used alone, but on both the main axis as well as on lateral branches when used together with GA₃ and TIBA. Floral buds were not produced on lateral branches when plants were treated with GA₃, TIBA and IAA all together. GA₃ and TIBA induced floral buds even under non-inductive photoperiods, the number of buds and reproductive nodes being less in TIBA- than in GA₃-treated plants during 24-h photoperiods. The time taken for floral buds to initiate with GA₃ and TIBA during noninductive photoperiods is much longer than that during 8-h inductive photoperiods with or without GA₃ or TIBA application. IAA completely inhibits the GA₃- and TIBA-caused induction during 24-h, but only delays it and reduces the number of reproductive nodes and floral buds during 16-h photoperiods.     

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.     

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; )     

Abscisic acid and apical dominance in Phaseolus coccineus L.

Abscisic acid (ABA) in lanolin, applied to the internode of decapitated runner bean plants enhances the outgrowth of lateral buds. The optimum concentration of the paste is 10^-5 M. The effect of ABA is counteracted by indoleacetic acid (IAA) but not by gibberellic acid (GA₃). There is no effect when ABA is applied to the apical bud or lateral buds of intact plants. However, 13.2 ng given to the lateral buds of decapitated plants stimulate their growth, whereas higher concentrations are inhibitory. Consequently, ABA enhances growth of lateral buds directly, but only when apical dominance is already weakened. The growth of the decapitated 2^nd internode was not affected by ABA. Radioactivity from [2-¹⁴C] ABA, applied to nonelongating 2^nd internode stumps of decapitated runner bean plants moves to the lateral buds, whereas [1-¹⁴C]IAA-and [³H]GA₁-translocation is much weaker. ABA transport is inhibited if IAA or [³H]GA₁ is applied simultaneously. In elongating internodes [¹⁴C]ABA is almost completely immobile. [¹⁴C]IAA-and [³H]GA₁-translocation is not affected by ABA. The amount of radioactivity from labelled ABA, translocated to the lateral buds, is highest during the early stages of bud outgrowth.Abbreviations ABA 2,4-cis, trans-(+)-abscisic acid - GA gibberellic acid - IAA indoleacetic acid - p.l. plain lanolin     

Actinomycin D Inhibits the GA3-Induced Elongation of Azuki Bean Epicotyls and the Reorientation of Cortical Microtubules

Actinomycin D inhibited the elongation of epicotyl segmentsfrom azuki bean seedlings that was induced by simultaneous treatmentwith IAA and GA₃. The drug also inhibited the elongation ofthe segments that was caused by IAA alone when it was appliedtogether with IAA. When the segments were pretreated with GA₃and then incubated with IAA, GA₃ promoted the elongation causedby IAA and brought about a predominance of transverse corticalmicrotubules (MTs) in the epidermal cells of the segments. Thechange in the arrangement of MTs caused by pretreatment withGA₃ was evident 1 h after the start of subsequent incubationwith IAA when the effect of pretreatment with GA₃ on the elongationhad not yet become apparent. Pretreatment with GA₃ did not causeany change in the arrangement of MTs when GA₃-pretreated segmentswere not incubated subsequently with IAA. Although actinomycinD applied before treatment with IAA did not inhibit the IAA-inducedelongation, the drug diminished the promotion of the elongationcaused by pretreatment with GA₃ and prevented GA₃ from bringingabout a predominance of transverse MTs when the drug was appliedduring the pretreatment with GA₃. GA₃-induced synthesis of mRNA seems to be involved in the promotionby GA₃ of IAA-induced elongation and in the GA₃-induced rearrangementof cortical MTs. (Received June 15, 1993; Accepted August 16, 1993)     

Tuberization in Potato at High Temperatures: Gibberellin Content and Transport from Buds

Warm temperatures (35°C day/30°C night) which inhibittuberization in potato (Solanum tuberosum L., cv. Sebago) increasedgibberellin activity in crude extracts from buds, but not frommature leaves, as determined by the lettuce hypocotyl bioassay.Changes in the growth of tubers and stolons indicate the occurrenceof basipetal movement of GA₃ applied to the terminal bud ora mature leaf. ¹⁴C labelling from GA₃ or mevalonic acid injectedjust below the terminal bud was recovered in the lower shoot,stolons and tubers, but the amount transported was greater atcool temperatures (20/15°C). It is concluded that high temperaturespromote the synthesis of gibberellin in the buds rather thantransport to the stolons. Solanum tuberosum L., potato, tuberization, gibberellin     

The Relationship between Levels of Endogenous Gibberellins and the Response of Vigna Hypocotyls to Exogenous Indole-3-Acetic Acid

Segments excised from the upper and the lower parts of cowpea(Vigna unguiculata L.) hypocotyls were compared in terms oftheir responses to exogenous indole-3-acetic acid (IAA) in relationto their endogenous levels of gibberellin. Growth of the segmentswas measured continuously during xylem perfusion with a lineardifferential transformer. IAA induced a burst of elongationin the upper segments but only slight promotion of growth inthe lower segments. Treatment with uniconazole, a potent inhibitorof the biosynthesis of gibberellins, reduced the responsivenessof the upper segments to exogenous IAA to about one half ofthe control value. Pre-perfusion with GA₃ of such segments fortwo hours prior to application of IAA, partially restored theresponsiveness to IAA. Analysis by GC/MS identified GA₁, GA₄,GA₉ GA₂₀ and GA₅₁ as native gibberellins in the hypocotyls ofcowpea seedlings. Analysis by GC/SIM also showed that the physiologicallyactive gibberellins (GA₁ and GA₄) were located mainly in theupper part of the hypocotyl and the treatment with uniconazolemarketly reduced the endogenous level of gibberellins thereto less than 11% of the control level. These results suggestthat levels of endogenous gibberellins possibly control theresponse to IAA in these segments. (Received May 12, 1994; Accepted November 15, 1994)     

GA3和IAA对慈竹综纤维和叶绿素含量动态积累的调控效应

以慈竹为材料,研究不同浓度和配比的GA₃和IAA对综纤维和叶绿素含量动态积累的调控效应,为纸浆用竹的遗传改良研究提供理论依据。研究结果表明, GA₃和IAA处理对慈竹综纤维动态积累调控作用具有差异。处理前30 d内,GA₃50IAA200处理慈竹综纤维积累强度高于GA₃200IAA50处理,40~50 d时,则反之。GA₃和IAA处理的综纤维最终水平明显高于空白对照,差异达极显著水平。GA₃和IAA处理能提高慈竹叶绿素含量,GA₃200IAA50处理慈竹叶绿素含量高于GA₃50IAA200处理。相关分析结果表明,叶绿素含量与综纤维含量间呈不显著正相关关系。