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1.
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, GA 1, by promoting GA 1 biosynthesis and by inhibiting GA 1 deactivation. These effects are mediated by changes in expression of key GA biosynthesis and deactivation genes. In particular, auxin promotes the step GA 20 to GA 1, 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 GA 1. After excision, the level of GA 1 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 GA 20 to GA 1 is impaired. These results indicate that, at least in excised segments, auxin partly promotes elongation by increasing the content of GA 1. 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 GA 1 application, despite being auxin-deficient. Finally, unlike the maintenance of GA 1 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
2.
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 A 1 (GA 1) 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 GA 1 above the application site markedly, nor that of GA 1 precursors above or below it. When plants were treated with [ 13C, 3H]GA 20, TIBA reduced dramatically the level of [ 13C, 3H]GA 1 recovered below the TIBA application site. The internodes treated with auxin transport inhibitors appeared to be still in
the phase where endogenous GA 1 affects elongation, as indicated by the strong response to applied GA 1 by internodes of a GA 1-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.
The effects of Tris-(2-diethylaminoethyl)-phosphate trihydrochloride (SK&F 7997-A 3) on the development of 4 varieties of Pisum sativum were investigated. The compound inhibited shoot elongation of all 4 varieties by as much as 50% or more when seeds were soaked in solutions of the inhibitor for 12 hours before planting. Seed treatment also affected flowering by causing an increase in the number of nodes to the first flower in the early varieties Little Marvel and Alaska. The number of nodes preceding the first flower in the late varieties Dwarf and Tall Telephone was not affected by high concentrations of SK&F 7997-A 3, but low concentrations appeared to cause a slight reduction in the number of nodes to flower. The inhibitor had little effect on growth when applied to established seedlings; some slight inhibition was noted when high doses were applied to the shoot tip. SK&F 7997-A3 suppressed the growth response of dwarf and tall peas to exogenous GA3. The compound did not inhibit biosynthesis of gibberellin by Fusarium moniliformc when present in shaken liquid cultures at concentrations as high as 10 mg/ml. The inhibitor suppressed the action of applied GA3 on shoot elongation when the 2 chemicals were applied in 3 ways: 1) inhibitor on lowermost compound leaf and GA3 on shoot tip; 2) GA3 on lowermost leaf and inhibitor on shoot tip; and 3) soaking of seeds in the 2 compounds combined for 12 hours prior to planting. The third method of dual treatment yielded evidence that SK&F 7997-A3 interacts noncompetitively with GA3 in the regulation of shoot elongation. 相似文献
4.
The capacities of indole-3-acetic acid (IAA) and gibberellin A 3 (GA 3) to counteract the inhibitory effects of (2-chloroethyl) trimethylammonium chloride (CCC), 2-isopropyl-4-dimethylamino-5-methylphenyl-1-piperidinecarboxylate methyl chloride (Amo-1618), and N,N-dimethylaminosuccinamic acid (B-995) on hypocotyl elongation in light-grown cucumber ( Cucumis sativus L.) seedlings were investigated. One μg of GA 3 applied to the shoot tip was sufficient to completely nullify the effect of 10 μg of Amo-1618 or 25 μg of B-995 applied simultaneously to the shoot tip, and 10 μg of GA 3 completely counteracted the effect of 10 −3 m CCC added to the root medium. One μg of IAA counteracted the effect of 10 −3 m CCC in the root medium, but IAA did not nullify the action of either Amo-1618 or B-995. Experiments were conducted using 2 growth retardants simultaneously, which indicated that Amo-1618 and CCC inhibit a common process, namely GA biosynthesis, essential to hypocotyl elongation. However, since the effect of CCC was overcome by applications of both GA and IAA, growth retardation resulting from treatment with CCC apparently is not due solely to inhibition of GA biosynthesis. B-995 did not interact additively with either Amo-1618 or CCC, which suggests that B-995 affects a process different from those affected by the other 2 retardants. Thus, while inhibition evoked by B-995 is reversible by applied GA, the action of B-995 does not appear to be inhibition of GA biosynthesis. 相似文献
5.
The hypothesis that auxin and gibberellic acid (GA 3) 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. GA 3 by itself did not exert any effect on fiber differentiation. Combinatiosn of IAA with GA 3 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 GA 3 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 GA 3 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 GA 3 concentrations have an inhibitory effect on internode elongation, whereas low IAA/high GA 3 concentrations promote maximal stem elongation. 相似文献
6.
The excised, hooked bean hypocotyl was the system used to determine wheiher the ‘auxin- and gibberellin like’ effect of the lipoidal pollen extract, Brass in-complex (Br), were mediated through, or independent of, auxin and gibberellin. The morphogenetic events of hook opening and hypocotyl elongation in this system are regulated by auxin and gibberellin, respectively. Brassin complex, like IAA, elicited a book closure in (he dark and retarded its opening in red light. This effect was synergized by T1BA, IAA and the presence of the auxin-producing organs, the epicotyl and cotyledons. Br-elicited hook closure was inhibited by the antiauxin. PCIB. Both GA 3 and Br totally reversed the light inhibition of hypocotyl elongation. The GA 3-effect, but nol the Br elicited elongation, was overcome by Ancymidol. Hypocotyl elongation was partially inhibited by TIBA and PCIB. suggesting a possible auxin involvement also in this effect of Br. Br may elicit its growth responses through an effect on endogenous auxin levels, In this way it is different from other lipoidat growth regulators, such as the oleanimins which require the presence of exogenous growth regulators for activity. 相似文献
7.
Auxin activates pumping of protons from the symplast to theapoplast and causes hyperpolarization of the symplast membranein the elongation zone of Vigna stems prior to the accelerationof growth. This auxin-induced hyperpolarization has been studiedin most cases in hypocotyl segments excised from the elongationzone. In the present study, mature-zone segments were perfusedwith IAA by the xylem perfusion technique in an effort to determinewhether or not IAA has any effects in the mature zone. Althoughno hyperpolarization of the symplast membrane was observed uponthe perfusion with auxin alone, auxin-induced hyperpolarizationwas observed when mature-zone segments had been pretreated withGA 3, in the absence of an increase in the growth rate. Theseresults suggest that cells in the mature zone have lost theability to activate the proton-pumping machinery in responseto auxin but that this ability can be restored by treatmentwith GA 3. This effect of GA 3 suggests the possibility that theconcentration of gibberellin in a tissue controls one of thecell's responses to auxin, namely, activation of the protonpump. (Received January 10, 1994; Accepted June 11, 1994) 相似文献
8.
Fluoren-9-carboxylic acid acts not only as an auxin but also as an gibberellin-antagonist. In the standard pea straight test
(S 5 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 (S 1 section) which also responds to gibberellin was used. Interaction of FCA and IAA in the S 5 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 S 1 section, the stimulating effect of GA 3 was markedly inhibited by 0.1 mg/ l FCA; 10 mg/ l FCA was either additive or less than additive to GA 3. In the cucumber hypocotyl test FCA itself was inactive up to 100 μg/plant, but it inhibited the GA 3-induced elongation. This inhibition was overcome by increasing the dosage of GA 3. 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. 相似文献
9.
We examined the physiological effects of brassinosteroids (BRs) on early growth of Arabidopsis. Brassinazole (Brz), a BR biosynthesis inhibitor, was used to elucidate the significance of endogenous BRs. It inhibited growth of roots, hypocotyls, and cotyledonous leaf blades dose-dependently and independent of light conditions. This fact suggests that endogenous BRs are necessary for normal growth of individual organs of Arabidopsis in both photomorphogenetic and skotomorphogenetic programs. Exogenous brassinolide (BL) promoted hypocotyl elongation remarkably in light-grown seedlings. Cytological observation disclosed that BL-induced hypocotyl elongation was achieved through cell enlargement rather than cell division. Furthermore, a serial experiment with hormone inhibitors showed that BL induced hypocotyl elongation not through gibberellin and auxin actions. However, a synergistic relationship of BL with gibberellin A 3 (GA 3) and indole-3-acetic acid (IAA) was observed on elongation growth in light-grown hypocotyls, even though gibberellins have been reported to be additive to BR action in other plants. Taken together, our results show that BRs play an important role in the juvenile growth of Arabidopsis; moreover, BRs act on light-grown hypocotyl elongation independent of, but cooperatively with, gibberellins and auxin. 相似文献
10.
Reciprocal grafts, and applications of gibberellin (GA) and indoleacetic acid (IAA) were used to localize the site of control for stem elongation in cucumber ( Cucumis sativus L.). Dwarf and tall plants were reciprocally grafted to determine influence of stems and roots on stem elongation. At 21 days there were no significant differences in length between stems grafted to their own roots and those grafted to roots of the other type. GA 3, GA 4+7, and IAA were applied to seedlings with and without live apical buds. Seedlings with live apical buds responded to level of added GA, but not to added IAA. GA 4+7 was more effective than GA 3. Hypocotyls of tall plants responded more to both GA treatments than did those of the dwarves when both types had live apical buds. When either GA 4+7 or IAA was applied to seedlings with dead apical buds, elongation of the hypocotyl responded to level of the growth regulator, but there was no difference in response between the dwarf and tall plants. 相似文献
11.
Indole-3-acetyl- myo-inositol esters constitute 30% of the low molecular weight derivatives of indole-3-acetic acid (IAA) in seeds of Zea mays. [ 14C]Indole-3-acetyl- myo-inositol was applied to a cut in the endosperm of the seed and found to be transported from endosperm to shoot at 400 times the rate of transport of free IAA. The rate of transport of indole-3-acetyl- myo-inositol from endosperm to shoot was 6.3 picomoles per shoot per hour and thus adequate to serve as the seed auxin precursor for the free IAA diffusing downward from the shoot tip. Indole-3-acetyl- myo-inositol is the first seed auxin precursor to be identified. 相似文献
12.
Background and aims The concept of root-sourced chemical signals that affect shoot growth in response to drought is widely reported; in particular the role of ABA in regulating stomatal conductance has received much attention. ABA, alone, does not fully explain all the effects of abiotic stresses in the root zone on shoot architecture. An increase in mechanical impedance, which can occur on even relatively modest soil drying, results in reduced root and shoot growth, processes that are potentially regulated by gibberellins (GAs ). Methods In this study we explored the role of mechanical impedance and exogenous gibberellin (GA 3) on root and shoot architecture in wheat seedlings containing the Rht-B1a (tall), Rht-B1b (semi-dwarf) or Rht-B1c (dwarf) alleles in the April-Bearded or Mercia backgrounds. Our experiments were based on the use of the sand culture system which allows the mechanical impedance of the root growth environment to remain constant and independent of water and nutrient availability. We investigated the effects of the application of exogenous GA 3 to the root system. Results We found that impeding soil reduced leaf elongation in the tall and semi-dwarf lines, confirming the stunting effect of mechanical impedance which is widely reported. However, leaf elongation in the dwarf lines was not affected by root impedance. Application of GA 3 to the roots restored leaf elongation in the tall and semi-dwarf lines growing in impeding soil, with some growth response even in the dwarf line, the longest leaves being obtained when GA was applied to impeded roots of a tall line. Both exogenous GA and root impedance reduced the number of tillers, but there was no interaction with the Rht genotype. The genetic background did not affect the results. Conclusion We suggest that the GA signalling pathway has an unidentified role in the leaf elongation response to mechanical impedance to root growth. 相似文献
13.
The morphological effects of gibberellin A 3 (GA 3) on the dgtmutant of tomato were investigated. The mutant effectively showedthe normal range of responses, including a promotion of stemlength due to an increased number of longer internodes, a dramaticincrease in apical dominance, and effects on leaf shape andcolour. In the case of stem elongation, the quantitative responseof the mutant was greater than normal. The morphological abnormalitiescharacteristic of the dgt mutant, such as horizontal growth,a thin stem and hyponastic leaves, were not normalized by GA 3. It is concluded that the demonstrated lack of response to auxinof the dgt mutant does not impair its gibberellin responses. Tomato, gibberellin, auxin, mutant, shoot development 相似文献
14.
The growth and IAA-oxidase activity of light-grown cucumber seedlings (cv. Aonagajibae) were investigated in response to GA 3 and IAA. Both GA 3 and IAA induced significant elongation of the hypocotyl. The fresh and dry weights of the hypocotyl increased due to GA 3 or IAA treatment, whereas no significant change was observed in the cotyledons of GA 3-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 GA 3 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 GA 3- or IAA-induced elongation and IAA-oxidase activity in the hypocotyl. The auxin-mediated mechanism for gibberellin action was discussed. 相似文献
15.
IAA-induced growth of light-grown cucumber hypocotyl sectionsis markedly enhanced by GA 3-pretreatment of the sections; thereis a distinct synergism between IAA and GA 3. Water pretreatmentalso enhances IAA-induced growth. On the other hand, IAA-pretreatedsections showed practically no further growth in response topost treatment with GA 3. The enhancing effect of GA 3 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 GA 3 can be observed soon after posttreatment with IAA. The response of GA 3-pretreated sectionsto IAA is greater in pretreatment with higher concentrationsof GA 3, and higher degrees of synergism between IAA and GA 3are obtained at IAA concentrations less than 10 -4 M. This synergisticinteraction between GA 3 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; ) 相似文献
16.
Prohexadione, a gibberellin (GA) biosynthesis inhibitor, was applied in ethanol around the circumference at the midpoint of the previous year terminal shoot of dormant Pinus sylvestris seedlings. After cultivating the seedlings under environmental conditions favorable for growth for 10 weeks, longitudinal and cambial growth were measured, and the endogenous levels of GA 1, GA 3, GA 4, GA 9, and indole-3-acetic acid (IAA) were determined by combined gas chromatography-mass spectrometry, using deuterated GAs and [ 13C 6]IAA as internal standards. Prohexadione application inhibited elongation and xylem and phloem production in the current year terminal shoot and xylem production in the previous year terminal shoots. Concomitantly, in both ages of shoots the cambial region contents of GA 1; GA 3, and GA 4 were decreased, whereas the level of GA 9 was increased. However, the IAA content was not altered in the terminal bud on the current year terminal shoot or in the cambial region of the current year or previous year terminal shoots. The results provide additional evidence that: (1) GAs are involved in the regulation of cambial growth, as well as longitudinal growth, in Pinus sylvestris shoots; (2) they act directly, rather than indirectly, by altering the IAA level; and (3) the GA 9 GA 4 GA 1 pathway is a major route of GA biosynthesis in conifer species.Abbreviations GA
gibberellin
- IAA
indole-3-acetic acid
- HPLC
high performance liquid chromatography
- GC
gas chromatography
- SIM
selected ion monitoring
- MS
mass spectrometry 相似文献
17.
Pulvini of excised segments from oats ( Avena sativa L. cv Victory) were treated unilaterally with indoleacetic acid (IAA) or gibberellic acid (GA 3) with or without gravistimulation to assess the effect of gravistimulation on hormone action. Optimum pulvinus elongation growth (millimeters) and segment curvature (degrees) over 24 hours were produced by 100 micromolar IAA in vertical segments. The curvature response to IAA at levels greater than 100 micromolar, applied to the lower sides of gravistimulated (90°) pulvini, was significantly less than the response to identical levels in vertical segments. Furthermore, the bending response of pulvini to 100 micromolar IAA did not vary significantly over a range of presentation angles between 0 and 90°. In contrast, the response to IAA at levels less than 10 micromolar, with gravistimulation, was approximately the sum of the responses to gravistimulation alone and to IAA without gravistimulation. This was observed over a range of presentation angles. Also, GA 3 (0.3-30 micromolar) applied to the lower sides of horizontal segments significantly enhanced pulvinus growth and segment curvature, although exogenous GA 3 over a range of concentrations had no effect on pulvinus elongation growth or segment curvature in vertical segments. The response to GA 3 (10 micromolar) plus IAA (1.0 or 100 micromolar) was additive for either vertical or horizontal segments. These results indicate that gravistimulation produces changes in pulvinus responsiveness to both IAA and GA 3 and that the changes are unique for each growth regulator. It is suggested that the changes in responsiveness may result from processes at the cellular level other than changes in hormonal sensitivity. 相似文献
18.
During the entire period of internode growth of Merremia emarginata contents of gibberellic acid (GA 3), 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 GA 3 contents were high as compared to other hormones; however, no significant role of GA 3 was discernible in elongation growth. Conjugated ABA contents remained very low during the elongation growth and increased
thereafter. 相似文献
19.
Plant hormones are important biotic factors to regulate root growth. Among the seven kinds of plant hormones, auxin and gibberellin (GA) are strong accelerators of shoot growth, but these are not always accelerators for root growth. The classical views of root-growth regulation by auxin and gibberellin are summarized and current theory of the regulation mechanism is described in this review. The concentration-dependent deceleration of root growth is a key to understanding the auxin action on roots, since the endogenous concentration of indole-3-acetic acid (IAA) is inversely proportional to the growth rate. As massive IAA is transported from shoots to roots by polar transport, the influx speed of IAA mainly controls IAA levels in root cells. The classical view of IAA transport in roots has been supported by recent discoveries of IAA-carrier proteins such as AUX1, PINs and MDRs. The role of plasma membrane-located H +-ATPase and its regulation by IAA has also been described for the acid growth phenomenon caused by the acidification of root cell walls. Compared to auxins, GA functions in roots are less remarkable. Nevertheless, GA also plays an indispensable role in the normal development of roots, since artificial GA-depletion causes abnormal expansion and suppression of root elongation. The GA-requirement for normal root growth was unveiled by the use of chemical inhibitors and mutants of GA biosynthesis. GA function that keeps root morphology long and slender is ascribed to the arrangement of cortical microtubules, cellulose microfibrils and unknown additional factor(s). Cross talks among plant hormones were recently found in the signal transduction pathways mainly in aerial organs. GA and IAA de-repress gene expression by degrading the gene-repressing proteins via the ubiquitin-mediated proteasome system. Another interaction of IAA and GA in growth regulation is the enhancement of GA1 level by IAA. Since the final biochemical steps of growth regulation take place in cell walls, possible cross talks are also conceivable in cell wall formation and modification. 相似文献
20.
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 (GA 3 or GA 1) and 4-Cl-IAA had a synergistic effect on pericarp growth. In the present study, we found that simultaneous application of
IAA and GA 3 to deseeded pericarps inhibited GA 3-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
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