The transport of radiolabeled indoleacetic acid and its conjugates in nodal stem segments of Phaseolus vulgaris L.

The transport of radiolabeled indoleacetic acid (IAA), and some of its conjugates, was investigated in nodal stem segments of Phaseolus vulgaris L. Donor agar blocks containing either [2-acetyl-¹⁴C]-IAA; [2-acetyl-¹⁴C]-indole-3-acetyl-L-aspartate (IAAsp); [2-acetyl-¹⁴C]-indole-3-acetyl-L-glycine (IAGly); or [2-acetyl-¹⁴C]-indole-3-acetyl-L-alanine (IAAla) were placed on either the apical or basal cut surface of stem segments each bearing an axillary bud at the midline. In some experiments, a receiver block was placed on the end opposite to the donor. After transport was terminated, the segments were divided into five equal sections plus the bud, and the radioactivity of donors, receivers and each part of the stem segment was counted.For all four substances tested, the amount of ¹⁴C transported to the axillary bud from the base was the same or greater than that from the apical end. After basipetal transport, the distribution of ¹⁴C in the segment declined sharply from apex to base. The inverse was true for acropetal transport. Transport for the three IAA conjugates did not differ substantially from each other.The IAA transport inhibitor, N-1-naphthylphthalamic acid (NPA), inhibited basipetal ¹⁴C-IAA transport to the base of the stem segment but did not alter substantially the amount of ¹⁴C-IAA recovered from the bud. Transport of ¹⁴C-IAA from the apical end to all parts of the stem segment declined when the base of the section was treated with nonradioactive IAA. Taken together with data presented in the accompanying article [Tamas et al. (1989) Plant Growth Regul 8: 165–183], these results suggest that the transport of IAA plays a role in axillary bud growth regulation, but its effect does not depend on the accumulation of IAA in the axillary bud itself.     

Endogenous levels of abscisic acid,indole-3-acetic acid and benzyladenine during in vitro bud growth induction of Wild cherry (Prunus avium L.)

Levels of endogenous growth substances (abscisic acid: ABA; indole-3-acetic acid: IAA) and applied benzyladenine (BA) were quantified during the eight first days of in vitro propagation of Wild Cherry (Prunus avium L.). Axillary buds from the middle part of the explants started to grow at day 2, thus were released from apical dominance. Hormone levels were measured in the apical, median and basal parts of the explants using an avidin-biotin based enzyme-linked immunosorbent assay (ELISA) after a purification of the extracts by high performance liquid chromatography (HPLC). All hormones showed rapid and considerable changes during the first eight days of growth. Exogenous IBA was probably transformed into IAA mainly in the basal part of the explant, and BA penetrated quickly. ABA levels were transiently enhanced in the apical part of the explants bearing young leaves. These phenomena are discussed in connection with the axillary bud reactivation.     

植物生长调节剂对黑木相思优树腋芽增殖及生根的影响

为建立黑木相思(Acacia melanoxylon)快繁技术体系,以含1个腋芽的无菌茎段为材料,研究了植物生长调节剂对其增殖和生根的影响。结果表明,6-BA 极易诱导黑木相思愈伤组织形成,但芽长势较差,不利于腋芽增殖体系的建立。而生长素既能诱导黑木相思生根,又能诱导腋芽增殖;将无菌茎段接入MS+IAA 0.5 mg L^-1+IBA 0.5 mg L^-1培养基中培养20 d的生根率为98.41%,培养40 d的腋芽增殖倍数为2.36,单株繁殖系数为6.57。这是首次成功建立高效、简便的生根和增殖同步发生的黑木相思直接器官发生途径的组培技术体系。     

In vitro adventitious bud regeneration from internode segments of beech

Internode explants collected from in vitro grown shoots of two clones of Fagus sylvatica L. (European beech) and five clones of F. orientalis Lipski (Oriental beech) were used to evaluate their bud regeneration capacity. Adventitious shoot-buds formed on callus, which developed from internode segments cultured in a Woody Plant Medium supplemented with different concentrations of either thidiazuron (TDZ) or benzyladenine (BA). After 4 weeks of culture on induction media, the explants were transferred to a proliferation medium supplemented with 2.2 μM BA, 9.1 μM zeatin and 2.9 μM indole-3-acetic acid (IAA) for another 8 weeks. Medium containing TDZ was much more efficient than medium containing BA in inducing adventitious buds, the optimal TDZ concentration being 4.5 μM and the optimal BA concentration 17.8 μM. Genotypic variation in shoot regeneration capacity was observed among the two Fagus species and between clones within each species, with a significant interaction between TDZ concentration and genotype regarding mean bud number. Thidiazuron induction medium supplemented with a range of individual auxins was investigated, and it was found that IAA or indole-3-butyric acid at 2.9 μM enhanced the bud forming capacity of explants. Morphogenic response varied significantly with the position of the internode along the stem. The highest regeneration potential was obtained from apical internodes, while those distal to the apex were the least productive. Elongated shoots of adventitious origin can be readily proliferated by axillary branching. This revised version was published online in June 2006 with corrections to the Cover Date.     

Effect of phytoregulators and physiological characteristics of the explants on micropropagation of Maytenus ilicifolia

Micropropagated shoots of Maytenus ilicifolia Mart. were obtained from axillary buds cultured in Murashige & Skoog medium supplemented with 13.3 M 6-benzyladenine (BA). Addition of 1.1 M 1-indole-3-acetic acid (IAA) to the medium increased shoot elongation. The number of shoots formed was influenced by BA concentration, degree of juvenility of the explant, and by bud explant position on the stem. Cultures of buds taken from stem parts located close to the shoot tip yielded more callus than shoots, whereas axillary buds at distant positions from the apical bud yielded more shoots.Abbreviations BA 6-benzyladenine - IAA indole-3-acetic-acid     

Role of indoleacetic Acid and abscisic Acid in the correlative control by fruits of axillary bud development and leaf senescence

When fully filled pods of bean plants were deseeded, the rate of axillary bud growth and the chlorophyll content of leaves were increased. Application of 0.1% indoleacetic acid (IAA) in lanolin on the deseeded pods caused abscission of axillary buds, inhibited growth of the remaining buds, and decreased leaf chlorophyll content. The response of bud development to fruit-applied IAA was concentration dependent between 0.001 and 0.1% IAA (representing from 2 to 200 micrograms IAA per fruit) resulting in greater growth inhibition at higher IAA concentrations.     

Rapid in vitro propagation of Aloe barbadensis Mill

Axillary bud development and adventitious bud formation was obtained with decapitated shoot explants of Aloe barbadensis Mill. Maximal bud growth and rooting of shoots was obtained on a modified medium of Murashige and Skoog supplemented with 5 M IBA. More adventitious and axillary buds developed on nutrient media supplemented with IBA than with NAA. Axillary buds but not adventitious buds developed with IAA in the medium. Morphogenesis was inhibited by 2,4-D. Kinetin, benzyladenine and thidiazuron were toxic to the explants and did not stimulate the development of axillary of adventitious buds. The optimal temperature for bud growth and development was 25°C. Axillary bud growth and the formation of adventitious buds was slowed down at 10°C and totally inhibited by 30°C. The optimal sucrose concentration was 3% with the inhibition of bud growth and development by higher sucrose levels.     

Response to strigolactone treatment in chrysanthemum axillary buds is influenced by auxin transport inhibition and sucrose availability

Axillary bud outgrowth is regulated by both environmental cues and internal plant hormone signaling. Central to this regulation is the balance between auxins, cytokinins, and strigolactones. Auxins are transported basipetally and inhibit the axillary bud outgrowth indirectly by either restricting auxin export from the axillary buds to the stem (canalization model) or inducing strigolactone biosynthesis and limiting cytokinin levels (second messenger model). Both models have supporting evidence and are not mutually exclusive. In this study, we used a modified split-plate bioassay to apply different plant growth regulators to isolated stem segments of chrysanthemum and measure their effect on axillary bud growth. Results showed axillary bud outgrowth in the bioassay within 5 days after nodal stem excision. Treatments with apical auxin (IAA) inhibited bud outgrowth which was counteracted by treatments with basal cytokinins (TDZ, zeatin, 2-ip). Treatments with basal strigolactone (GR24) could inhibit axillary bud growth without an apical auxin treatment. GR24 inhibition of axillary buds could be counteracted with auxin transport inhibitors (TIBA and NPA). Treatments with sucrose in the medium resulted in stronger axillary bud growth, which could be inhibited with apical auxin treatment but not with basal strigolactone treatment. These observations provide support for both the canalization model and the second messenger model with, on the one hand, the influence of auxin transport on strigolactone inhibition of axillary buds and, on the other hand, the inhibition of axillary bud growth by strigolactone without an apical auxin source. The inability of GR24 to inhibit bud growth in a sucrose treatment raises an interesting question about the role of strigolactone and sucrose in axillary bud outgrowth and calls for further investigation.     

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     

STUDIES ON THE FLORAL HISTOGENESIS AND PHYSIOLOGY OF PERILLA. III. EFFECTS OF INDOLEACETIC ACID ON THE FLOWERING OF APICAL BUDS AND EXPLANTS IN CULTURE

Raghavan , V. (Princeton U., Princeton, N. J.) Studies on the floral histogenesis and physiology of Perilla. III. Effects of indoleacetic acid on the flowering of apical buds and explants in culture. Amer. Jour. Bot. 48(10): 870–876. Illus. 1961.—The responses of apical buds and explants of a short-day plant, Perilla frutescens (L.) Britt. var. 'Tall Late,' when grown in vitro in White's medium supplemented with indoleacetic acid (IAA) and subjected to short-days (SD) or long-days (LD), are described. Additions of varying concentrations of IAA to the medium inhibited the flowering of the photoinduced apical buds in 2 ways. There was a progressive delay in the appearance of the first signs at the apex and a gradual transition from the more flower-like structures in lower concentrations of IAA (0.1 mg/liter) to sterile cones in higher doses. The sterile cones had florets with well-developed calyx and corolla lobes, but lacked the sporogenous tissues. When subjected to LD, visible signs were observed only in buds grown in 0.1 and 1.0 mg/liter IAA, the pronounced effect of the auxin being in the step-wise inhibition in the formation of the non-sporogenous tissues of the differentiating florets. Flowering of the explants with the 1st pair of unfolded leaves was also inhibited by IAA in either SD or LD, but the 1st signs appeared relatively faster than in apical buds. When photoinduced, explants with the 1st and 2nd pairs of unfolded leaves flowered in all concentrations of IAA tried (up to 100 mg/liter) while those kept in LD remained entirely vegetative.     

The effect of growth substances on Verticillium wilt of tomato plants

This paper describes the effects of a number of growth-regulating substances on the development of disease in tomato plants caused by Verticillium albo-atrum. Indole-acetic acid usually reduced disease and also reduced the number of hyphae in the stem but it increased tylosis; low concentrations slightly stimulated disease development. Some control of disease was obtained by removing apical buds, and axillary shoots as they developed. When the apical bud alone was removed, developing axillary shoots sometimes wilted; this did not occur in plants with intact buds. Gibberellic acid increased disease in susceptible plants and also induced symptoms in resistant plants. Maleic hydrazide greatly reduced growth of plants, made them more diseased and stimulated growth of the parasite in the vessels. Of other growth-regulating substances tested, 2,4,6-trichlorophenoxy-acetic acid, 2,3,5-triiodobenzoic acid and 2,4-dichlorophenoxyacetic acid increased disease at some concentrations and reduced it at others. Cycocel (2-chloroethyl) trimethyl ammonium chloride and naphthaleneacetamide, gave good control of disease over a range of concentrations when applied to the soil in which plants were growing. Treatments which reduced disease also reduced the growth of the parasite in the shoot and stimulated the formation of tyloses. Indole and 2,4-dichloroanisole had some effect on disease development but this was much less than that induced by the other substances.     

In vitro propagation of Leucocroton havanensis Borhidi (Euphorbiaceae): A rare serpentine-endemic species of Cuba

Leucocroton havanensis Borhidi is an endemic plant species of Cuba able to hyperaccumulate nickel. In order to sustain the conservation of this species, an efficient protocol for its micropropagation, via axillary bud proliferation, is described. We placed apical segments from aseptic seedlings on basal medium supplemented with indole-3-acetic acid (IAA) and 6-benzylaminopurine (BAP) or thidiazuron (TDZ), individually or in combination. On a medium containing 0.5 mg L^?1 IAA and 1.0 mg L^?1 BAP explants (65.5%) developed axillary buds. Nevertheless, combinations of 0.5 mg L^?1 IAA with 0.1 mg L^?1 TDZ was the most effective treatment producing the highest number of buds per explant (30.3); while the control treatment, without growth regulators, produced no buds at all. Transfer of buds to medium supplemented with indole-3-butyric acid, indicated that 0.25 mg L^?1 is the amount of hormone required to generate roots on young buds (100%). In order to assess DNA variations in micropropagated plants, an Amplified Fragment Length Polymorphism analysis was performed and no genetic variation was detected. This study demonstrates that a high multiplication rate can be obtained by means of the reported protocol, and that plantlets can be readily hardened (96% survival) in a greenhouse by transplanting them on serpentine soil.     

Improvement of somatic embryogenesis in highland-papaya cell suspensions

Axillary buds (2 mm) from 3-year-old Carica pubescens Lenné et Koch (highland papaya) fruit-bearing plants grown in the greenhouse were cultivated in NN-medium supplemented with different growth regulators naphthaleneacetic acid and indoleacetic acid in combination with Zeatin, benzyladenine, Kinetin and thidiazuron. Several responses were observed within 2–3 months; namely, sprouting of the preformed axillary buds, bud branching into multiple shoots, callus formation at the basal end of the explant and somatic embryogenesis in the preformed callus. Somatic embryogenesis was frequent in most of the tested growth regulator combinations, with the exception of thidiazuron which showed no effect. A much higher yield of somatic embryos could be obtained in suspensions. Somatic embryogenesis was enhanced by the occurence of adventive embryogenesis on single embryos as globular embryo clusters. This was observed in cell suspensions initially grown in a WPM-medium with 2,4-dichlorophenoxyacetic acid, or in combination with benzyladenine or zeatin, for 6 days, then maintained in a growth regulator-free medium under continuous agitation (50 RPM) on an orbital shaker for 3 months. Single cells grown in the absence of 2,4-dichlorophenoxyacetic acid did not initiate embryogenesis and de-differentiated into callus. Plantlets were recovered after transfer of mature embryos from cell suspensions into Magenta flasks. In a second subculture, adventitious embryogenesis occurred spontaneously in clusters at the globular embryo stage under the same growth conditions, yielding a high number of embryos. The culture conditions described above allowed initiation of a large number of somatic embryos directly from cell suspensions through adventive somatic embryogenesis and indirectly from callus on axillary buds.Abbreviations 2,4-d dichlorophenoxyacetic acid - CH casein enzymatic hydrolysate - BA benzyladenine - FAA formalin:acetic acid:alcohol - Glu l-glutamine - IAA indoleacetic acid - NAA naphthaleneacetic acid - NN Nitsch and Nitsch-medium (1969) - TDZ thidiazuron - SD standard deviation     

Kinetin Transport to Axillary Buds of Dwarf Pea (Pisum sativum L.)

Decapitation resulted in the transport of significant amountsof ¹⁴C to the axillary buds from either point of application,but pretreatment of the cut internode surface of decapitatedplants with IAA (alone or in combination with unlabelled kinetin)inhibited the transport of label to the axillary buds and resultedin its accumulation in the IAA-treated region of the stem. Inintact plants to which labelled kinetin was applied to the apicalbud there was little movement of ¹⁴C beyond the internode subtendingthis bud; when labelled kinetin was applied to the roots ofintact plants, ¹⁴C accumulated in the stem and apical bud butwas not transported to the axillary buds. A considerable proportionof the applied radioactivity became incorporated into ethanol-insoluble/NaOH-solublecompounds in the apical bud of intact plants, in internodestreated with IAA, and in axillary buds released from dominanceby removal of the apical bud. The results are discussed in relation to the possible role ofhormone-directed transport of cytokinins m the regulation ofaxillary bud growth.     

Micropropagation of chinese redbud (<Emphasis Type="Italic">Cercis yunnanensis</Emphasis>) through axillary bud breaking and induction of adventitious shoots from leaf pieces

Summary Factors affecting in vitro shoot production and regeneration of Cercis yunnanensis Hu et Cheng were investigated by comparing various growth regulators and explant types. For optimum shoot production from axillary buds, Murashige and Skoog (MS) media containing 6-benzyladenine, either alone or in combination with a low concentration of thidiazuron, resulted in the greatest number of shoots formed per explant (>3). Explants (2 mm long) containing one axillary bud placed in directcontact with the medium yielded the most shoots per bud (1.6) when grown on growth regulator-free medium. Root formation on 70–80% of shoot explants was accomplished using either indole-3-butyric acid or α-naphthaleneacetic acid in the medium, with significantly more roots formed on explants possessing and apical bud than those without the bud. Direct shoot organogenesis from leaf explants occurred on MS medium containing 10–30 μM thidiazuron, with up to 42% of leaf explants producing shoots.     

Plant growth regulator and graft control of axillary bud formation and development in the TO-2 mutant tomato

The torosa-2 tomato mutant is characterized by a strong inhibition of release of axillary shoots, that is not under the control of the main apex and IAA. Microscopic examination indicated that about 70% of leaf axils do not have axillary buds. Of the growth regulators tested, gibberellic acid and cytokinins were able to modify the to-2 phenotype: increasing bud number (GA₃ treated) and developing shoots (both substances). Sequential application of growth regulators demonstrated that bud production was only affected by treatments given between sowing time and 32 days after germination. Grafting experiments indicated that endogenous root factors have no essential role in the lateral branching of the genotypes investigated. The control of axillary bud differentiation and the branching pattern in the to-2 appears to be dependent of a complex mechanism involving gibberellins and cytokinins.     

Changes in abscisic acid and indole-3-acetic acid in axillary buds of Elytrigia repens released from apical dominance

Growth of axillary buds on the rhizomes of Elytrigia repens (L) Nevski is strongly dominated by the rhizome apex, by mechanisms which may involve endogenous hormones. We determined the distribution of indole-3-acetic acid (IAA) and abscisic acid (ABA) in rhizomes and measured (by gas-chromatography-mass spectrometry) their content in axillary buds after rhizomes were decapitated. The same measurements were also made in buds induced to sprout by removing their subtending scale leaves. The ABA content tended to be higher in the apical bud and in the axillary buds than in the adjacent internodes, and tended to decline basipetally in the internodes and scale leaves. IAA was similary distributed, except that there was less difference between the buds and other rhizome parts. After rhizomes were decapitated, the ABA content of the first axillary bud declined to 20% of that of control values within 24 h, while the IAA content showed no marked tendency to change. The ABA content also declined within 12 h in the first axillary bud after rhizomes were denuded, while the content of IAA tended to increase after 6 h. These changes occurred before the length of the first axillary bud increased 24–48 h after rhizomes were decapitated or denuded. We conclude that the release of axillary buds from apical dominance in E. repens does not require IAA content to be reduced, but is associated with reduced ABA content.     

In vitro culture and plant regeneration of large flowered purslane

Culture conditions were established for callus induction from a range of Portulaca grandiflora Hook tissues. Rapidly growing calli were obtained on Murashige and Skoog medium with stem-, leaf- and sepal-derived explants. Plant regeneration via organogenesis was explant-origin dependent with hypocotyl tissues giving the highest shooting frequency. Light conditions, pH and carbon source had a pronounced effect on the percentage of explants regenerating buds and the number of buds formed. It was possible to establish stable regenerated plants in the glasshouse.Abbreviations BA 6-benzyladenine - 2,4-D 2,4-dichlorophenoxyacetic acid - NAA 1-naphthaleneacetic acid - IAA indoleacetic acid - MS Murashige and Skoog (1962) medium     

红厚壳茎段丛生芽诱导与植株再生

红厚壳(Calophyllum inophyllum)为藤黄科红厚壳属多年生木本植物,有很高的药用价值。该研究以红厚壳带节茎段为外植体,探讨生长调节剂对腋芽萌发及丛生芽诱导、伸长和试管苗生根的影响。研究结果表明,外植体腋芽萌发和丛生芽诱导效果最好的培养基是MS+NAA1.0+TDZ0.5,在此条件下培养21天后,转入添加0.5 g·L–1活性炭且无生长调节剂的MS培养基,可有效促进不定芽的伸长。将带不定芽的外植体先在附加1.0 mg·L–1NAA的1/2MS培养基上进行生根诱导4周,之后转入附加1.0 g·L–1活性炭的无激素培养基进行根的伸长培养,这样的两步生根法能有效促进红厚壳生根。     

Improved micropropagation in Polygala myrtifolia

Summary Stem segments from apical shoot tips of Polygala myrtifolia were used as primary explants to establish in vitro cultures. Axillary shoots produced on non-contaminated explants were excised and recultured in the same medium to increase the stock of shoot cultures. Equal molar concentrations of five cytokinins [2-isopentenyladenine, kinetin, zeatin, N ⁶-benzyladenine (BA), and adenine] were tested for ability to induce axillary shoot development from double-node stem segments. The highest rate of axillary shoot proliferation was induced on Murashige and Skoog agar medium supplemented with 1.8 μM BA. Seven indole-3-acetic acid (IAA) concentrations (0, 2.9, 5.7, 8.6, 11.4, 14.3, 17.1 μM) were tested to determine the optimum conditions for in vitro rooting of microshoots. Up to 72% of the microshoots rooted with 14.3 μM IAA. Other auxins tested, α-naphthaleneacetic acid and indole-3-butyric acid, were less effective than IAA in inducing adventitious root formation. All rooted plantlets having more than three roots were successfully established in soil.