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1.
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.  相似文献   

2.
Effects of Auxin Transport Inhibitors on Gibberellins in Pea   总被引:5,自引:0,他引:5  
The effects of the auxin transport inhibitors 2,3,5-triiodobenzoic acid (TIBA), 9-hydroxyfluorene-9-carboxylic acid (HFCA), and 1-N-naphthylphthalamic acid (NPA) on gibberellins (GAs) in the garden pea (Pisum sativum L.) were studied. Application of these compounds to elongating internodes of intact wild type plants reduced markedly the endogenous level of the bioactive gibberellin A1 (GA1) below the application site. Indole-3-acetic acid (IAA) levels were also reduced, as was internode elongation. The auxin transport inhibitors did not affect the level of endogenous GA1 above the application site markedly, nor that of GA1 precursors above or below it. When plants were treated with [13C,3H]GA20, TIBA reduced dramatically the level of [13C,3H]GA1 recovered below the TIBA application site. The internodes treated with auxin transport inhibitors appeared to be still in the phase where endogenous GA1 affects elongation, as indicated by the strong response to applied GA1 by internodes of a GA1-deficient line at the same stage of expansion. On the basis of the present results it is suggested that caution be exercised when attributing the developmental effects of auxin transport inhibitors to changes in IAA level alone. Received April 13, 1998; accepted April 14, 1998  相似文献   

3.
Aloni R 《Plant physiology》1979,63(4):609-614
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.  相似文献   

4.
During the entire period of internode growth of Merremia emarginata contents of gibberellic acid (GA3), phenyl-acetic acid (PAA), indole-3-acetic acid (IAA, free and conjugated) and abscisic acid (ABA, free and conjugated) were estimated by ELISA using polyclonal antibodies raised against each hormones. At the time of internode elongation free auxin content was low and increased with the decrease in the rate of elongation. In contrast, conjugated IAA showed declining trend where free IAA content was remarkably high, suggesting thereby that conjugated IAA might have mobilized during the later phase of internode development. The endogenous GA3 contents were high as compared to other hormones; however, no significant role of GA3 was discernible in elongation growth. Conjugated ABA contents remained very low during the elongation growth and increased thereafter.  相似文献   

5.
A binding site for auxins was found in the 50,000g pellet from a homogenate of shoots from dark-grown wheat seedlings. The optimum conditions for the binding of native auxin, IAA, were within the range of physiological conditions of growth (pH 5.2, temperature 20° C). The binding site displayed a high affinity to IAA (affinity constant about 107 M –1, i.e. dissociation constant about 10–8 M) and low capacity, 60 p mol per 1 g of fresh weight. The binding capacity of 3.5-days-old shoots is represented by about 56% and 44% of that of leaves and coleoptiles, respectively. The more rapidly growing leaves also contained more endogenous free IAA (64%) than the coleoptiles from the same seedlings (36%). The binding site was very specific, distinguishing well between strong auxins and structurally related substances which exhibit very weak auxin activity. These physiological properties of this binding site indicate that it may have a certain role in the regulation of physiological processes, such as elongation growth and cell division.  相似文献   

6.
Auxin-Gibberellin Interactions in Pea: Integrating the Old with the New   总被引:4,自引:1,他引:3  
Recent findings on auxin-gibberellin interactions in pea are reviewed, and related to those from studies conducted in the 1950s and 1960s. It is now clear that in elongating internodes, auxin maintains the level of the bioactive gibberellin, GA1, by promoting GA1 biosynthesis and by inhibiting GA1 deactivation. These effects are mediated by changes in expression of key GA biosynthesis and deactivation genes. In particular, auxin promotes the step GA20 to GA1, catalyzed by a GA 3-oxidase encoded by Mendel’s LE gene. We have used the traditional system of excised stem segments, in which auxin strongly promotes elongation, to investigate the importance for growth of auxin-induced GA1. After excision, the level of GA1 in wild-type (LE) stem segments rapidly drops, but the auxin indole-3-acetic acid (IAA) prevents this decrease. The growth response to IAA was greater in internode segments from LE plants than in segments from the le-1 mutant, in which the step GA20 to GA1 is impaired. These results indicate that, at least in excised segments, auxin partly promotes elongation by increasing the content of GA1. We also confirm that excised (light-grown) segments require exogenous auxin in order to respond to GA. On the other hand, decapitated internodes typically respond strongly to GA1 application, despite being auxin-deficient. Finally, unlike the maintenance of GA1 content by auxin, other known relationships among the growth-promoting hormones auxin, brassinosteroids, and GA do not appear to involve large changes in hormone level.  相似文献   

7.
The influence of total darkness versus a 16/8 photoperiod and of auxins added to the culture medium on the in vitro root formation capacity of Acacia mangium microshoots of juvenile and mature origin was examined. Rooting of the mature clone was significantly increased by exposing the microshoots to auxins (4 and 6 μM IAA or IBA) in darkness, while the promoting effect of darkness combined with 4 μM IAA was more time-restricted for the juvenile-origin microshoots. Overall, the latter rooted in greater proportions than those from the mature source. Maintaining the microshoots of both origins on auxin supplemented medium in darkness resulted in a greater number of adventitious roots formed than under the standard 16/8 lighting conditions. On the other hand, light stimulated root elongation. These results are discussed mainly from the viewpoint of auxin metabolism in relation to adventitious root formation. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

8.
Arabidopsis is a species that naturally displays the rosette form. Therefore, elucidation of the factors, which control basal leaf development, is of particular interest. Most evidence points that auxins and gibberellins are important in the control of rosette leaf development. In this paper, we report on a regimen that disrupts the normal rosette growth in Arabidopsis and induces internodal growth, which we have termed unbasal. The growth conditions are: (1) seed germination in the presence of 2,3,5-triiodobenzoic acid (TIBA); (2) transfer of the seedlings to a medium containing exogenous auxin (NAA) and GA3; (3) transfer of the seedlings to a GA3-only medium for all subsequent growth. Under these conditions, auxin and GA interact to induce internode elongation. Polar auxin transport appears to have a temporal effect on this synergistic interaction. In this regimen, GA increases auxin activity in the basal portions of the stem. Cross sectional morphology of the elongated internodes between two rosette leaves in an un-basal plant was similar to that seen for the pin1 Arabidopsis mutation.  相似文献   

9.
The effects of plant growth regulators were investigated onanthocyanin synthesis induced by removing auxin from carrotsuspension cultures. Of the auxins tested, 2,4-D showed thestrongest inhibiting effect on anthocyanin synthesis and hadthe strongest promoting effect on undifferentiated growth. When2,4-D was added to anthocyanin synthesizing cells, in whichcell division had ceased, anthocyanin synthesis was repressedimmediately, accumulated anthocyanin disappeared and cell divisionresumed. All cytokinins examined promoted anthocyanin synthesisin the absence of auxin. Both gibberellic acid (GA3) and abscisicacid inhibited anthocyanin synthesis in media lacking 2,4-D,though GA3 showed no effect on cell division. These effectsof growth regulators on anthocyanin synthesis are similar tothose reported for their effects on embryogenesis [Fujimuraand Komamine (1975) Plant Sci. Lett. 5: 359, (1979) Z. Pflanzenphysiol.95: 13, (1980) Z. PJlanzenphysiol. 99: 1]. The relationshipbetween the induction of anthocyanin synthesis, metabolic differentiation,and embryogenesis are discussed. 1 Present address: Department of Biology, College of Arts andSciences, The University of Tokyo, Komaba, Meguro-ku, Tokyo153, Japan. 2 Present address: Biological Institute, Faculty of Science,Tohoku University, Sendai, Miyagi 980, Japan. (Received November 28, 1985; Accepted July 23, 1986)  相似文献   

10.
The effects of intermittent immersion of Avena seedlings insolutions of IAA on the response of the coleoptiles to unilateralillumination in the region of that producing the second positivecurvature were studied by means of automatic time-lapse photographywhich enabled the growth-rate and curvature to be recorded simultaneously. Phototropic induction occurred even after the coleoptiles hadabsorbed sufficient IAA from a 10-4 M. solution to raise theirrate of elongation to about twice the normal value. Phototropiccurvature, which had been temporarily inhibited by a curvaturein the opposite direction induced by the IAA, became evidentas soon as this curvature had ceased to operate. In coleoptiles, supplied with IAA after the commencement ofa phototropic curvature, the response was temporarily suppressed.It was resumed as soon as the effects of the exogenous IAA haddisappeared. The ability of the coleoptiles to produce a slight phototropicresponse persisted even when their growth-rate had been greatlyreduced by previous removal of the endosperm. Increasing thegrowth-rate by supplying the starved seedlings with IAA or sucrose,separately or together, failed to increase the response. Decapitation did not prevent phototropic induction, but delayedthe onset of the response. Application of IAA by intermittentimmersion in a 0.1 mg./l. solution, after the decapitated coleoptileshad been exposed to unilateral illumination, increased the rateof growth but reduced the response. The results suggest that in these experiments phototropic inductionwas not mediated by any direct action of light on the displacement,inactivation, or rate of synthesis of an endogenous auxin. Theyare in agreement with the hypothesis that the stimulus causedan asymmetrical distribution of a co-factor of auxin.  相似文献   

11.
The interaction of auxins – IAA, IBA or NAA – with galactoglucomannan oligosaccharides (GGMOs) on adventitious root formation and elongation growth of mung bean hypocotyl cuttings was studied. GGMOs induced adventitious roots in the absence of auxins; however, their effect was lower compared with IBA or NAA. On the other hand, in the presence of auxins, GGMOs inhibited adventitious root induction. Their effect depended on the concentration of oligosaccharides and the type of auxin used. The highest inhibition effect of GGMOs at a concentration of 10−8 M in the presence of IBA and NAA was observed. In the presence of IAA their inhibition was non-significant in regard to the concentration. The interaction of auxins with GGMOs resulted in the formation of adventitious roots on a shorter part of hypocotyls compared with the effect of auxins alone. However, roots were induced more extensively along the hypocotyls treated with GGMOs compared with the control. GGMOs inhibited the length of induced adventitious roots in the presence of IAA, while in combination with IBA or NAA they were ineffective. The elongation of hypocotyls induced by IAA or IBA was inhibited by GGMOs, too. However, in the presence of NAA or by endogenous growth they were without any significant effect on elongation growth. These findings suggest that GGMOs in certain concentrations might inhibit rooting and the elongation process dependant on auxin used.  相似文献   

12.
Indole-3-acetic acid (IAA), fusicoccin and weak acids all lower the cytoplasmic pH (pHi) and induce elongation growth of maize (Zea mays L.) coleoptiles. Gibberellic acid (GA3) also induces elongation growth and we have used confocal laser scanning microscopy to study the effects of GA3 on pHi employing the pH-indicator dyes, 2,7-bis(2-carboxyethyl)-5-(and-6) carboxyfluorescein and carboxy-semi-naphthorhodafluor-1. We confirm that GA3 induces growth significantly in light-grown but only slightly or not at all in dark-grown coleoptiles. The growth induced by IAA treatment was similar in light- and dark-grown coleoptiles. The pHi decreased by up to 0.6 units during the first 7 min of GA3 or IAA treatment of both light- and dark-grown coleoptiles. Gibberellic acid inhibited IAA-induced growth of dark-grown coleoptiles. Hence, in dark-grown coleoptiles GA3 may activate either directly or indirectly reactions that interfere with the signalling pathway leading to elongation growth. The possible role of pHi in growth is discussed.Abbreviations ABA abscisic acid - AM acetoxymethyl ester - BCECF 2,7-bis(2-carboxyethyl)-5-(and-6) carboxyfluorescein - [Ca2+]i cytoplasmic free calcium - GA(n) gibberellin A(n) - GA3 gibberellic acid - IAA indole-3-acetic acid - PGR plant growth regulator - pHi cytoplasmic pH - Pipes piperazine-N,N-bis[2-ethanesulfonic acid] - Snarf-1 carboxy-semi-naphthorhodafluor-1 We thank Dr R. King (CSIRO, Canberra) for providing the GA1 and T. Phillips for processing the photographic material. H.R. Irving was supported by an Australian Research Council Research Fellowship and the work was supported by an Australian Research Council grant.  相似文献   

13.
A. Hager  R. Schmidt 《Planta》1968,83(4):347-371
Summary Short illumination of excised coleoptiles (with or without apex) inhibits the subsequent transport of IAA-2-14C in these sections during darkness.To a certain extent the inhibition is dependent both on the light intensity and on the duration of illumination. Only the blue region of the visible spectrum is effective.The light induced inhibition is due to a decrease of the quantity of IAA transported; on the other hand, the velocity of transport remains unchanged.The inhibition of auxin transport can be observed only if coleoptiles contain endogenous or fed auxin during the preceding illumination period. Besides illumination inhibition of auxin transport can also be brought about by incubation of coleoptile sections with a previously illuminated IAA/FMN solution.Auxin transformed by peroxidase operates in the same way. The different oxidation products of IAA in the solutions used were identified: The only product which inhibits elongation growth and auxin transport was 3-M. The conversion of IAA to 3-M is accomplished by crude cell-free extracts from corn coleoptiles.An increased formation of labeled 3-M from IAA-2-14C during illumination of coleoptiles could be demonstrated.Since 3-M is not actively transported in coleoptiles, it must be assumed that 3-M functions as an inhibitor of auxin transport only at its site of formation.It is concluded that the phototropic curvature of coleoptiles and stems is triggered by the photooxidative formation of 3-M from IAA in the side exposed to light. The flow of growth substances will be partly blocked by 3-M in this side and can be directed to the shaded side.On the strength of these findings some phenomena of phototropism (transmission of stimulus, mneme, quantum yield) can easily be explained.
Abkürzungen FMN Flayinmononucleotid - IES Indol-3-essigsäure - 3-M 3-Methylenoxindol - NES -Naphthylessigsäure Herrn Prof. Dr. L. Brauner zum 70. Geburtstag in Dankbarkeit gewidmet.  相似文献   

14.
R. J. Rose  D. Adamson 《Planta》1969,88(3):274-281
Summary -irradiated wheat seed (500 kr) produces coleoptiles that grow without cell division or DNA synthesis. Apart from an initial 24-hr delay in growth, intact coleoptiles have a pattern of cell elongation similar to normal coleoptiles. The elongation of coleoptiles excised at a size of 2 mm, when the cells are small and just prior to entering a rapid elongation phase, is promoted by kinetin and gibberellic acid (GA3). Elongation of coleoptiles excised at 8 mm, when the cells are larger and in the rapid elongation phase, is promoted by indoleacetic acid (IAA). This sequential response to growth substances in coleoptiles is remarkably similar to that in normal coleoptiles. The GA3 response in excised coleoptiles is not inhibited by FUDR, confirming that DNA synthesis is not required for GA3-induced elongation in coleoptiles.  相似文献   

15.
Soybean is an important oilseed crop grown globally. However, two examples of environmental stresses that drastically regulate soybean growth are low light and high-temperature. Emerging evidence suggests a possible interconnection between these two environmental stimuli. Low light and high-temperature as individual factors have been reported to regulate plant hypocotyl elongation. However, their interactive signal effect on soybean growth and development remains largely unclear. Here, we report that gibberellins (GAs) and auxin are required for soybean hypocotyl elongation under low light and high-temperature interaction. Our analysis indicated that low light and high-temperature interaction enhanced the regulation of soybean hypocotyl elongation and that the endogenous GA3, GA7, indole-3-acetic acid (IAA), and indole-3-pyruvate (IPA) contents significantly increased. Again, analysis of the effect of exogenous phytohormones and biosynthesis inhibitors treatments showed that exogenous GA, IAA, and paclobutrazol (PAC), 2, 3, 5,-triiodobenzoic acid (TIBA) treatments significantly regulated soybean seedlings growth under low light and high-temperature interaction. Further qRT-PCR analysis showed that the expression level of GA biosynthesis pathway genes (GmGA3ox1, GmGA3ox2 and GmGA3) and auxin biosynthesis pathway genes (GmYUCCA3, GmYUCCA5 and GmYUCCA7) significantly increased under (i) low light and high-temperature interaction and (ii) exogenous GA and IAA treatments. Altogether, these observations support the hypothesis that gibberellins and auxin regulate soybean hypocotyl elongation under low light and high-temperature stress interaction.  相似文献   

16.
Flower opening in Iris (Iris × hollandica) requires elongation of the pedicel and ovary. This moves the floral bud upwards, thereby allowing the tepals to move laterally. Flower opening is requires with elongation of the pedicel and ovary. In cv. Blue Magic, we investigated the possible role of hormones other than ethylene in pedicel and ovary elongation and flower opening. Exogenous salicylic acid (SA) and the cytokinins benzyladenine (N6-benzyladenine, BA) and zeatin did not affect opening. Jasmonic acid (JA) and abscisic acid (ABA) were slightly inhibitory, but an inhibitor of ABA synthesis (norflurazon) was without effect. Flower opening was promoted by gibberellic acid (GA3), but two inhibitors of gibberellin synthesis (4-hydroxy-5-isopropyl-2-methylphenyltrimethyl ammonium chloride-1-piperidine carboxylate, AMO-1618; ancymidol) did not change opening. The auxins indoleacetic acid (IAA) and naphthaleneacetic acid (NAA) strongly promoted elongation and opening. An inhibitor of auxin transport (2,3,5-triodobenzoic acid, TIBA) and an inhibitor of auxin effects [α-(p-chlorophenoxy)-isobutyric acid; PCIB] inhibited elongation and opening. The data suggest that endogenous auxins are among the regulators of the pedicel and ovary elongation and thus of flower opening in Iris.  相似文献   

17.
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.  相似文献   

18.
Yang T  Davies PJ  Reid JB 《Plant physiology》1996,110(3):1029-1034
Exogenous gibberellin (GA) and auxin (indoleacetic acid [IAA]) strongly stimulated stem elongation in dwarf GA1-deficient le mutants of light-grown pea (Pisum sativum L.): IAA elicited a sharp increase in growth rate after 20 min followed by a slow decline; the GA response had a longer lag (3 h) and growth increased gradually with time. These responses were additive. The effect of GA was mainly in internodes less than 25% expanded, whereas that of IAA was in the older, elongating internodes. IAA stimulated growth by cell extension; GA stimulated growth by an increase in cell length and cell number. Dwarf lkb GA-response-mutant plants elongated poorly in response to GA (accounted for by an increase in cell number) but were very responsive to IAA. GA produced a substantial elongation in lkb plants only in the presence of IAA. Because lkb plants contain low levels of IAA, growth suppression in dwarf lkb mutants seems to be due to a deficiency in endogenous auxin. GA may enhance the auxin induction of cell elongation but cannot promote elongation in the absence of auxin. The effect of GA may, in part, be mediated by auxin. Auxin and GA control separate processes that together contribute to stem elongation. A deficiency in either leads to a dwarfed phenotype.  相似文献   

19.
This study explores the unique growth-regulatory roles of two naturally occurring auxins, indole-3-acetic acid (IAA) and 4-chloroindole-3-acetic acid (4-Cl-IAA), and their interactions with gibberellin (GA) during early pea (Pisum sativum L.) fruit development. We have previously shown that 4-Cl-IAA can replace the seed requirement in pea pericarp growth (length and fresh weight), whereas IAA had no effect or was inhibitory. When applied simultaneously, gibberellin (GA3 or GA1) and 4-Cl-IAA had a synergistic effect on pericarp growth. In the present study, we found that simultaneous application of IAA and GA3 to deseeded pericarps inhibited GA3-stimulated growth. The inhibitory effect of IAA on GA-stimulated growth was mimicked by treatment with ethephon (ethylene releasing agent), and the inhibitory effects of IAA and ethylene on GA-mediated growth were reversed by silver thiosulfate (STS), an ethylene action inhibitor. Although pretreatment with STS could retard senescence of IAA-treated pericarps, STS pretreatment did not lead to IAA-induced pericarp growth. Although 4-Cl-IAA stimulated growth whereas IAA was ineffective, both auxins induced similar levels of ethylene evolution. However, only 4-Cl-IAA-stimulated growth was insensitive to the effects of ethylene. Gibberellin treatment did not influence the amount of ethylene released from pericarps in the presence or absence of either auxin. We propose a growth regulatory role for 4-Cl-IAA through induction of GA biosynthesis and inhibition of ethylene action. Additionally, ethylene (IAA-induced or IAA-independent) may inhibit GA responses under physiological conditions that limit fruit growth.  相似文献   

20.
Auxins control growth and development in plants, including lateral rootinitiation and root gravity response. However, how endogenous auxin regulatesthese processes is poorly understood. In this study, the effects of auxins onlateral root initiation and root gravity response in rice were investigatedusing a lateral rootless mutant Lrt1, which fails to formlateral roots and shows a reduced root gravity response. Exogenous applicationof IBA to the Lrt1 mutant restored both lateral rootinitiation and root gravitropism. However, application of IAA, a major form ofnatural auxin, restored only root gravitropic response but not lateral rootinitiation. These results suggest that IBA is more effective than IAA in lateralroot formation and that IBA also plays an important role in root gravitropicresponse in rice. The application of NAA restored lateral root initiation, butdid not completely restore root gravitropism. Root elongation assays ofLrt1 displayed resistance to 2,4-D, NAA, IBA, and IAA.This result suggests that the reduced sensitivity to exogenous auxins may be due tothe altered auxin activity in the root, thereby affecting root morphology inLrt1.  相似文献   

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