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)     

Do growth substances regulate the phloem as well as the xylem transport of nutrients to the strawberry receptacle?

Fruits of first or second order of strawberry cv. Talisman were used for the experiments. Fourteen d after pollination they were deprived of achenes and the receptacles were treated for 3 d with a mixture of indoleacetic acid (IAA), gibberellic acid (GA₃) and kinetin at a concentration of 3·10^-4 M. Then [¹⁴C]sucrose and ³²PO ₄ ^3- were applied to the surface of the leaves or to the root medium. Only the transport from the leaves, not from roots, underwent hormonal stimulation; moreover, both markers were affected by the growth regulators to a similar degree.Abbreviations GA₃ gibberellicacid - IAA indole-3-aceticacid     

Gibberellin-induced ethylene production and its effect on cowpea epicotyl elongation

The effect of gibberellin A₁ (GA₁) on production of ethylene by cowpea (Vigna sinensis cv Blackeye pea no. 5) epicotyl explants and its relationship to epicotyl elongation was investigated. The explants were placed upright in water and incubated in sealed culture tubes or in large jars. GA, and IAA in ethanol solution were injected into the subapical tissues of the decapitated epicotyls. Cowpea epicotyl explants elongated after GA but not after IAA treatment, and they were very sensitive to exogenous ethylene. As little as 0.14 1/1 ethylene reduced significantly GA₁-induced epicotyl elongation.Treatment with GA₁ induced the production of ethylene which began 10 h after GA application, showed a peak at about 22 h and then declined. The yield of ethylene was proportional to the amount of GA, injected. The inhibition of epicotyl elongation in closed tubes was avoided by absorbing ethylene released with Hg(Cl0₄)₂ , or by adding AVG to the incubation solution to inhibit ethylene production. Treatment with IAA elicited a rapid production of ethylene which ceased about 10 h after application. The effects of IAA and GA₁ on ethylene production were additive.Abbreviations AVG aminoethoxyvinylglycine 2-amino-4-(2-aminoethoxy)-trans-3butenoic acid - ACC 1-aminocyclopropane-1-carboxylic acid - GA gibberellin - IAA indole-3-acetic acid     

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...     

Gibberellin-mediated synergism of xylogenesis in lettuce pith cultures

Major gibberellins (GAs) in lettuce (Lactuca sativa L. cv Romaine) pith explants have been identified by gas chromatography-mass spectrometry (GC-MS) or GC-selected ion monitoring (GC-SIM) as GA₁, 3-epi-GA₁, GA₈, GA₁₉, and GA₂₀. Treatment of pith explants with indole-3-acetic acid (IAA) (57 micromolar) plus kinetic (0.5 micromolar) induced xylogenesis. In this xylogenic treatment, the concentration of a biologically active, polar GA-like substance(s) increased during the first 2 days of culture, although all of the above GAs decreased (as measured by GC-SIM). In non-xylogenic treatments, where explants were cultured without exogenous hormones, or with IAA or kinetin alone, the concentration of the biologically active, polar GA-like substance(s) decreased during the first two days of culture, as did all of the above GAs (as measured by GC-SIM). Treatment of pith explants with exogenous GA₁ alone did not induce xylogenesis, but GA₁ at very low concentrations (0.0014 and 0.003 micromolar) synergized xylogenesis in the IAA plus kinetin-treated cultures. These results suggest that changes in the concentration of certain endogenous GAs may be involved in xylogenesis mediated by IAA plus kinetin in lettuce pith cultures.     

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.     

A Possible Role for Indoleacetic Acid, Low Temperature, and Phospholipid Metabolism in the Induction of GA(3) Responsiveness in GA(3) Insensitive (Rht3-Containing) Dwarf Wheat Aleurone

Preincubation of dwarf, Rht3-containing deembryonated seed for 4 hours in 342 nanomolar indoleacetic acid (IAA) induced maximum sensitivity to GA₃. In addition, the 4-hour IAA pretreatment caused a 2-fold increase in total phospholipids which coincided identically on a temporal basis with the induced GA₃ sensitivity. Changes in absolute levels of individual phospholipids and their acyl groups were recorded and compared with the changes observed in several Rht-containing aleurone tissues which were induced to develop GA₃ sensitivity by exposure to low temperature (5°C). Several distinct similarities between all tissues were recorded as they develop GA₃ sensitivity. One parameter, the percentage phospholipid composition, was quite similar in all tissues after they had become maximally sensitive to GA₃, suggesting that there is at least one membrane phospholipid composition which is particularly responsive to GA₃. The results indicate that (a) the basis of the GA₃ insensitivity of the Rht mutation resides in an aberrant phospholipid/fatty acid composition and/or metabolism; (b) exposure to low temperature (5°C) for 20 hours or longer, or 342 nanomolar IAA for 4 hours or longer reverses or corrects the genetic lesion, enabling the tissue to adopt a GA₃ responsive membrane composition. Finally, an hypothesis is discussed which indicates that IAA may play a controlling role in the mobilization of endospermal reserves, at least in Rht3-containing wheat aleurone.     

Hormonal regulation of fruit set, parthenogenesis induction and fruit expansion in Japanese pear

The effects of applied gibberellins (GAs), GA₁, GA₃, GA₄ and GA₇ with a cytokinin, N-(2-chloro-4-pyridyl)-N′-phenylurea (CPPU) and indole-3-acetic acid (IAA) on fruit set, parthenogenesis induction and fruit expansion of a number of Rosaceae species were assessed. These included Japanese pear cv. ‘Akibae’ (self-compatible) and cv. ‘Iwate yamanashi’ (a seedless cultivar). Other Rosaceae species (Pyrus communis, Chaenomeles sinensis, Cydonia oblonga, and Malus pumila) were also investigated. GA₄, GA₇ and CPPU are very effective in inducing parthenocarpic fruit growth, whereas GA₁, GA₃ and IAA, have no ability to induce parthenogenesis in Japanese pear. GA₄- and GA₇-induced parthenocarpic fruit tended to be smaller in size, higher in flesh hardness, and showed advanced fruit ripening in comparison to pollinated fruit and to parthenocarpic fruit induced by CPPU. GA₄- and GA₇-induced parthenocarpic fruit also had an increased pedicel length and fruit shape index and also showed a slight protrusion of the calyx end. CPPU, GA₄ and GA₇ alone or combination with uniconazole were also active in inducing parthenogenesis in three other Rosaceae species, although final fruit set was extremely low. GA₁ was essentially inactive in promoting fruit expansion unlike the other bioactive GAs, whose effectiveness in promoting fruit cell expansion was as follow: GA₄ ≈ GA₇ > GA₃ > GA₁.     

Activity of Various Growth Substances in the Avena First Internode Test

The elongation growth of the Avena first internode segments was studied in the presence of one or several of the following growth substances: indoleacetic acid (IAA), 6-fur-furylamino purine (FAP, kinetin), 6-benzylamino purine (BAP), gibberellin A₃ (GA₃) and A₄₊₇ (GA₄₊₇), and abscisic acid (ABA). The cytokinins at concentrations of 10^?7 to 10^?6M stimulated growth with 4 to 6 per cent but this effect was not statistically significant. Concentrations higher than 5 × 10^?6M inhibited growth. FAP and BAP (from 10^?8M to 10^?6M) had no significant interaction with any other growth substance used. The two-factor interactions of IAA × ABA, IAA × GA₃, and GA₃× ABA, as well as the three-factor interaction IAA × ABA × GA₃ were significant. However, the IAA × ABA interaction was significant only when high concentration (10^?6M) of ABA was used. The growth inhibition produced by 10^?7 and 10^?6M ABA was overcome by about equimolar concentrations of IAA. The stimulation of growth by GA₃ and GA₄₊₇ (10^?9 to 10^?7M) was prevented by simultaneous application of ABA, and it was reduced significantly by application of IAA (10^?7 to 10^?8M). GA3 at 10^?8M combined with different concentrations of IAA gave slightly higher elongation than IAA alone but the observed values were significantly lower than expected assuming independent additive action.     

Relationship of IAA-oxidase Activity to Gibberellinand IAA-induced Elongation of Light-grown Cucumber Seedlings

The growth and IAA-oxidase activity of light-grown cucumber seedlings (cv. Aonagajibae) were investigated in response to GA₃ and IAA. Both GA₃ and IAA induced significant elongation of the hypocotyl. The fresh and dry weights of the hypocotyl increased due to GA₃ or IAA treatment, whereas no significant change was observed in the cotyledons of GA₃-treated seedlings as compared with the controls. The fresh and dry weights of IAA-treated cotyledons were both lower than those of controls. Treatment with GA₃ or IAA resulted in retardation of IAA-oxidase activity in the hypocotyl and cotyledons. The degree of retardation was less in the cotyledons than in the hypocotyl. An inverse relationship was recognized between GA₃- or IAA-induced elongation and IAA-oxidase activity in the hypocotyl. The auxin-mediated mechanism for gibberellin action was discussed.     

Blockage by gibberellic Acid of phytochrome effects on growth, auxin responses, and flavonoid synthesis in etiolated pea internodes

Red light inhibits the growth of etiolated pea internodes, causes a shift toward higher indoleacetic acid (IAA) concentrations in the IAA dose-response curve of excised sections, and promotes the synthesis in intact internodes of kaempferol-3-triglucoside. Gibberellic acid (GA₃) prevents all 3 effects, the first effect substantially and the last 2 completely. This suggests GA₃ blockage of an early or basic event initiated by the active form of phytochrome. The red light-induced shift in the IAA dose-response curve of excised sections is consistent with a light-induced increase in the activity of an IAA destruction system, since the magnitude of the red light inhibition varied with IAA concentration. The red light and GA₃ effects on growth and on flavonoid synthesis are consistent with the view that phytochrome may control growth by regulating the synthesis of phenolic compounds which act as cofactors in an IAA-oxidase system. GA₃ reversal of the red light-induced shift in the IAA dose-response curve involves both growth promotion and inhibition by GA₃ at different IAA concentrations and this, together with the GA₃ reversal of light-induced flavonoid synthesis, supports the suggested regulatory role of phenolic compounds in growth.     

Effect of relative hormone concentration on auxin-gibberellin interaction in correlative inhibition of axillary buds

Summary Indole-3-acetic acid (IAA) applied to the fully elongated second internode of decapitated Phaseolus multiflorus plants always inhibited axillary bud elongation at concentrations down to 100 g/g lanolin, whereas gibberellic acid (GA₃) enhanced bud elongation at concentrations down to 1000 g/g lanolin. Lower concentrations than these of either IAA or GA₃ were without significant effect. All possible combinations of IAA and GA₃ within the concentration range 10¹ to 10⁵ g/g lanolin were antagonistic; IAA tending to inhibit, and GA₃ promote, axillary bud elongation growth. Treatment of an elongating internode with the hormones resulted in an increase in inhibition of bud growth by IAA in the presence of GA₃.     

Role of auxin and gibberellin in differentiation of primary Phloem fibers

The hypothesis that auxin and gibberellic acid (GA₃) control the differentiation of primary phloem fibers is confirmed for the stem of Coleus blumei Benth. Indoleacetic acid (IAA) alone sufficed to cause the differentiation of a few primary phloem fibers. In long term experiments auxin induced a considerable number of fibers in mature internodes. GA₃ by itself did not exert any effect on fiber differentiation. Combinatiosn of IAA with GA₃ completely replaced the role of the leaves in primary phloem fiber differentiation qualitatively and quantitatively. Although the combined effect of the two growth hormones diminished considerably with increasing distance from the source of induction, auxin with GA₃ or IAA alone induced fibers in a few internodes below the application site. When various combinations of both hormones were applied, high concentrations of IAA stimulated rapid differentiation of fibers with thick secondary walls, while high levels of GA₃ resulted in long fibers with thin walls. The size of the primary phloem fibers correlated with the dimensions of the differentiating internode, thereby providing evidence that both growth regulators figure in the control of stem extension. High IAA/low GA₃ concentrations have an inhibitory effect on internode elongation, whereas low IAA/high GA₃ concentrations promote maximal stem elongation.     

Influence of gibberellic acid on auxin biosynthesis and their effects on coleoptile elongation in garlic

To demonstrate the effect of auxin on intact coleoptile growth, garlic (Allium sativum L.) cloves were inoculated in agar supplemented with DW (control), GA₃ and GA₃+tryptophan (a precursor of IAA, GA₃+T). The coleoptiles were harvested at 24 h intervals to measure growth in terms of length, activities of IAAld DH (which convert tryptophan to IAA) and peroxidase (that oxidizes IAA). Contents of endogenous IAA and PAA were also measured by indirect ELISA. Peroxidase activity was suppressed by GA₃ treatment and increased by GA₃+T treatment. Although endogenous contents of IAA were increased by the addition of GA₃ and even more by GA₃+T in the media, there was no further increase in coleoptile length, suggesting that garlic coleoptiles are sufficient in their production of IAA.     

Effect of Gibberellin A3 on the Elongation, α-Amylase Activity, Reducing Sugar Content and Oxygen-uptake of the Leaf Sheath of Dwarf Maize Seedlings

GA₃-treatment of dwarf maize seedlings resulted in the elongation of the leaf sheath and also an increase in α-amylase activity. Excised leaf sheaths did not respond to GA₃ in leaf shealh length and α-amylase activity. Increase in the enzyme activity is always accompanied by an increase in the length of the leaf sheath. α-Amylase activity gradually increased as the growth of the first leaf proceeded, and a parallelism was found between the length of the leaf sheath and the enzyme activity, suggesting that the degree, of the enzyme activity depends on the length of the leaf sheath. On the other hand, IAA did not affect α-amylase activity while it promoted leaf sheath elongation. This suggests that elongation per se is not associated with the increase in α-amylase activity and that the enzyme-promoting effect is specific to gibberellin. Higher α-amylase activity and lower content of reducing sugars were detected in the older tissue of the leaf sheath, that is, in the upper half. This was the same for GAlrealed seedlings. The amount of reducing sugars was less in GA₃-trealcd seedlings. Oxygen-uptake of the leaf sheath was higher in the upper half in both controls and GA₃-treated seedlings. It was slightly higher in the latter than in the former. From these results it was discussed 1o conclude that the processes of the GA₃-induced elongation and increase in α-amylase activity of the leaf sheath are independent of one another.     

Phytohormone Profiling During Tuber Development of Chinese Yam by Ultra-high performance Liquid Chromatography–Triple Quadrupole Tandem Mass Spectrometry

Changes in agronomic characters and the profile of various endogenous phytohormones during tuber development were studied in Dioscorea opposite (Chinese yam) cv. Guihuai 16. Tuber development exhibited a sigmoidal growth pattern according to the changes in tuber agronomic characters. The growth cycle of yam tuber could be divided into three stages: initiation stage, enlargement stage, and maturation stage. Moreover, the enlargement stage could be separated into three phases—slow growth phase, rapid growth phase, and late growth phase. Endogenous changes in phytohormones were associated with developmental changes in the tubers. The pulses of bioactive gibberellins (such as GA₃ and GA₄) were measured in tubers. The highest contents of GA₃ and GA₄ were reached 90 days after field planting, corresponding to the beginning of the rapid growth phase of tuber enlargement. Changes in trans-zeatin (tZ), jasmonic acid (JA), indole-3-acetic acid (IAA), and abscisic acid (ABA) levels were also observed, and seemed to be related to tuber enlargement at different phases. Continuous increases in JA and tZ contents accompanied tuber enlargement. Transient pulses of both IAA and ABA contents were also observed at the start of tuber rapid growth. Additionally, a second peak level of IAA was detected at the tuber maturation stage. These results suggest GAs play a key role at the beginning of the tuber rapid growth stage, and there is a close relationship between whole tuber enlargement and the contents of JA and tZ. Moreover, it is suggested that IAA and ABA also may be linked to the beginning of tuber rapid growth, and IAA also seems to be correlated to late tuber maturation.     

Short-term kinetics of elongation growth of gibberellin-responsive lettuce hypocotyl sections

The short-term kinetics of growth of the excised lettuce (Lactuca sativa L.) hypocotyl were characterized with respect to the effects of gibberellic acid (GA₃), indole-3-acetic acid (IAA), KCl and pH. A Hall-device-based, miniaturized, linear displacement transducer was developed to measure the growth of 2-mm hypocotyl sections with 1-m resolution. Following treatment with GA₃, a lag time of less than 10 min was typically followed by an increase in growth rate with two acceleration phases, reaching a final elevated rate within about 1 h. The kinetics of the response to GA₁, a mixture of GA₄ and GA₇, and GA₉ were similar to the response to GA₃. There was no response to IAA treatment either in the presence or absence of GA₃. KCl alone had no effect on the growth rate, but caused an increase in rate when added after GA₃, with a lag time of usually less than 1 h. Responses to pH changes had lag times of a few minutes in all cases. A shift from H₂O to pH 6 buffer inhibited growth, while a shift from H₂O to pH 4 buffer resulted in a transient increase to a rate comparable to that induced by GA₃. A shift from pH 6 to pH 5 caused an increase in growth rate, followed by a gradual decline to an H₂O control rate after more than an hour. The responses to GA₃ at pH 4 and pH 5 were similar to that found for addition of GA₃ to water controls.Abbreviations GA gibberellin - GA₃ gibberellic acid - GA₁, GA₄₊₇, GA₉ gibberellins A₁, A₄₊₇, A₉ - IAA indole-3-acetic acid     

The mode of action of a morphactin,fluoren-9-carboxylic acid

Fluoren-9-carboxylic acid acts not only as an auxin but also as an gibberellin-antagonist. In the standard pea straight test (S₅ section) for auxin it stimulated elongation, the optimum concentration being 10 mg/l. On the other hand, it inhibited elongation at 0.1 mg/l. This inhibitory effect was more marked when younger tissue (S₁ section) which also responds to gibberellin was used. Interaction of FCA and IAA in the S₅ section has shown that at higher concentration of IAA there seemed to be a suppraoptimal effect, indicating that FCA acted as an auxin. However, in the S₁ section, the stimulating effect of GA₃ was markedly inhibited by 0.1 mg/l FCA; 10 mg/l FCA was either additive or less than additive to GA₃. In the cucumber hypocotyl test FCA itself was inactive up to 100 μg/plant, but it inhibited the GA₃-induced elongation. This inhibition was overcome by increasing the dosage of GA₃. In the same material, the IAA-induced elongation was not affected by FCA. These results indicate that whether FCA acts as an auxin or a gibberellin-antagonist depends on whether the tissue is sensitive to gibberellin and/or auxin.     

Plant Growth-promototing Activities of Mercaptriazinone Derivatives

Twenty-nine mercaptotriazinone derivatives were synthesized and their plant growth-promoting activities were examined by the rice (Oryza sativa) seedling test in the presence or absence of gibberellic acid (GA₃). For high activity in promoting the GA₃-induced shoot elongation, an isopropyl or an appropriately substituted phenyl group, a hydrogen atom and a lower alkyl thio group were required in the 1-, 3-and 4-positions, respectively, of the 1,3,5-triazine-2,6-dione structure. In more detailed experiments, 4-methylthio-1-(p-tolyl)-s-triazine-2,6(1H, 3H)-dione, one of the most potent mercaptotriazinones, was found to synergistically promote the GA₃-induced elongation of the first and second leaves of rice seedlings. Several mercaptotriazinone derivatives, active or inactive, in the rice seedling test were examined by the radish (Raphanus sativus) leaf disk expansion test, but all of them were completely inactive. Structure-activity relationships of mercaptotriazinone derivatives are discussed in relation to those of the corresponding alkoxytriazinone derivatives.     

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; )