共查询到20条相似文献,搜索用时 15 毫秒
1.
Jan G. H. M. Rijnders Young-Yell Yang Yuji Kamiya Nobuta Takahashi Gerard W. M. Barendse Cornelis W. P. M. Blom Laurentius A. C. J. Voesenek 《Planta》1997,203(1):20-25
The role of gibberellin (GA) and ethylene in submergence-induced petiole elongation was studied in two species of the genus
Rumex. Analysis of endogenous GAs in the flooding-tolerant Rumex palustris Sm. and the intolerant Rumex acetosa L. by gas chromatography-mass spectrometry showed for both species the presence of GA1, GA4, GA9, GA19, GA20 and GA53. Gas chromatography-mass spectrometry analysis of R. palustris petiole tissue of submerged plants showed an increase in levels of 13-OH GAs, especially GA1, compared with drained plants. This effect could be mimicked by application of 5 μL L−1 ethylene. In R. acetosa, no differences between levels of GAs in drained or submerged plants were found. In R. palustris, both submergence and ethylene treatment sensitized petioles to exogenous gibberellic acid (GA3). In R. acetosa the effect was opposite, i.e. submergence and ethylene de-sensitized petioles to GA3. Our results demonstrate the dual effect of ethylene in the submergence response related to flooding tolerance, i.e. in the
flooding-tolerant R. palustris ethylene causes an increased concentration of and sensitivity to GA with respect to petiole elongation while in the intolerant
R. acetosa ethylene reduces growth independent of GAs.
Received: 5 November 1996 / Accepted: 8 February 1997 相似文献
2.
Stem elongation in Fuchsia × hybrida was influenced by cultivation at different day and night temperatures or in different light qualities. Internode elongation
of plants grown at a day (25°C) to night (15°C) temperature difference (DIF+10) in white light was almost twofold that of
plants grown at the opposite temperature regime (DIF−10). Orange light resulted in a threefold stimulation of internode elongation
compared with white light DIF−10. Surprisingly, internode elongation in orange light was similar for plants grown at DIF−10
and DIF+10. Flower development was accelerated at DIF−10 compared with DIF+10 in both white and orange light. To examine whether
the effects of DIF and light quality on shoot elongation were related to changes in gibberellin metabolism or plant sensitivity
to gibberellins (GAs), the stem elongation responses of paclobutrazol-treated plants to applied gibberellins were determined.
In the absence of applied gibberellins paclobutrazol (>0.32 μmol plant−1) strongly retarded shoot elongation. This inhibition was nullified by the application of about 10–32 nmol of GA1, GA4, GA9, GA15, GA19, GA20, GA24, or GA44. The results are discussed in relation to possible effects of DIF and light quality on endogenous gibberellin levels and
gibberellin sensitivity of fuchsia and their effects on stem elongation.
Received October 4, 1997; accepted December 17, 1997 相似文献
3.
Ethephon (Eth), gibberellin A3, A4 + 7 (GA3, GA4 + 7), and 6-benzyladenine (BA) removed secondary dormancy of Amaranthus caudatus seeds. The GAs and BA potentiated the effect of ethephon or 1-aminocyclopropane-1-carboxylic acid (ACC), an ethylene biosynthesis
precursor, in terms of the rate or final percent of germination. Aminoethoxyvinylglycine (AVG), an ACC synthase activity inhibitor,
was observed to simultaneously inhibit the release from dormancy effected by GA3 or BA as well as the ethylene production stimulated by these regulators. Breaking of secondary dormancy by GA3, GA4 + 7 or BA was prevented by 2,5-norbornadiene (NBD), an inhibitor of ethylene binding. Ethylene completely or markedly reversed
the inhibitory effect of NBD. We thus conclude that the removal of secondary dormancy in Amaranthus caudatus seeds by gibberellin or benzyladenine involves ethylene biosynthesis and action. 相似文献
4.
In young plants of Salix pentandra, a temperate zone deciduous woody species, elongation growth ceases and a terminal bud is formed at day lengths shorter than
a critical length. This is the first step in dormancy development, making survival under harsh winter conditions possible.
Early studies strongly indicate that gibberellin is involved in the photoperiodic control of bud set and bud break. GA1 action was studied by application under short days to plants where cessation of shoot elongation had occurred, followed by
subsequent anatomic investigations of shoot tips. Under short days the frequency of cell division decreased rapidly along
with the earlier observed decrease in GA1 levels. Application of GA1 to short-day–induced terminal buds rapidly stimulated cell division in apices several days before visible shoot elongation
in response to this treatment was observed. One day after GA1 application a fourfold increase in cell division frequency in apices was observed, increasing to a maximum of sevenfold 2
days after application. Long-day treatment leading to induction of bud break after about 4–6 days was followed by slowly increasing
frequency of cell divisions. In earlier studies of this species, short days and gibberellins had no effect on cell elongation.
These data show that increased GA1 content, by application or long-day treatment, results in increased frequency of mitosis. This strongly indicates that GA1 affects stem elongation in connection with bud set and bud break primarily by affecting cell divisions in subapical tissues.
Received February 26, 1999; accepted October 8, 1999 相似文献
5.
B. Tudzynski 《Applied microbiology and biotechnology》1999,52(3):298-310
Gibberellins (GAs) are a large family of isoprenoid plant hormones, some of which are bioactive growth regulators, controlling
seed germination, stem elongation, and flowering. The rice pathogen Gibberella fujikuroi (mating population C) is able to produce large amounts of GAs, especially the bioactive compounds gibberellic acid (GA3) and its precursors, GA4 and GA7. The main steps of the biosynthetic pathway have long been established from the identification of intermediates in wild-type
G. fujikuroi and mutant strains. However, the genetics of the fungus have been rather under-developed, and molecular genetic studies of
the GA pathway started just recently. The progress in researching GA biosynthesis in the last 2 years resulted primarily from
development of the molecular tools, e.g. transformation systems for the fungus, and cloning the genes encoding GA biosynthesis
enzymes, such as the bifunctional ent-copalyl diphosphate/kaurene synthase and several cytochrome P450 monooxygenases. The availability of these genes opened new
horizons both for detailed study of the pathway and the regulation mechanisms at the molecular level, and for modern strain
improvement programs. This review gives a short overview of the well-known physiological and biochemical studies and concentrates
mainly on the new molecular genetic data from GA research, including new information on the regulation of GA biosynthesis.
Received: 15 February 1999 / Received revision: 16 April 1999 / Accepted: 16 April 1999 相似文献
6.
Tetsushi Azuma Tomoko Hatanaka Naotsugu Uchida Takeshi Yasuda 《Plant Growth Regulation》2003,41(2):105-109
The enhancement of internodal elongation in floating or deepwater rice (Oryza sativa L. cv. Habiganj Aman II) by treatment with ethylene or gibberellic acid (GA3) at high relative humidity (RH) is inhibited by abscisic acid (ABA). Here, we examined the interactive effects of ethylene, gibberellin (GA) and ABA at low RH on internodal elongation of deepwater rice stem segments. Although ethylene alone hardly promoted internodal elongation of stem sections at 30% RH, it enhanced the internodal elongation induced by GA3. Application of ABA alone to stem segments had no effect on internodal elongation. However, in the presence of ethylene and GA3 at 30% RH, ABA further promoted internodal elongation. This promotive effect of ABA was not found in the internodes of stem segments treated either with ethylene or with GA3 at 30% RH or in the internodes of stem segments treated with ethylene and/or GA3 at 100% RH. 相似文献
7.
Development of Nitrogen Assimilation Enzymes during Photoautotrophic Growth of Chenopodium rubrum Suspension Cultures 总被引:2,自引:0,他引:2
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We have shown previously that ethylene, which accumulates in the air spaces of submerged stem sections of rice (Oryza sativa L. cv “Habiganj Aman II”), is involved in regulating the growth response caused by submergence. The role of gibberellins in the submergence response was studied using tetcyclacis (TCY), a new plant growth retardant, which inhibits gibberellin biosynthesis. Stem sections excised from plants that had been watered with a solution of 1 micromolar TCY for 7 to 10 days did not elongate when submerged in the same solution or when exposed to 1 microliter per liter ethylene in air. Gibberellic acid (GA3) at 0.3 micromolar overcame the effect of TCY and restored the rapid internodal elongation in submerged and ethylene-treated sections to the levels observed in control sections that had not been treated with TCY. The effect of 0.01 to 0.2 micromolar GA3 on internodal elongation was enhanced two- to eight-fold when 1 microliter per liter ethylene was added to the air passing through the chamber in which the sections were incubated. GA3 and ethylene caused a similar increase in cell division and cell elongation in rice internodes. Thus, ethylene may cause internodal elongation in rice by increasing the activity of endogenous GAs. In internodes from which the leaf sheath had been peeled off, growth in response to submergence, ethylene and GA3 was severely inhibited by light. 相似文献
8.
Dongsu Choi 《Journal of Plant Biology》2007,50(5):595-599
Ethylene decreases the content of endogenous abscisic acid (ABA) and increases the level of bioactive gibberellin A1 (GA1) in the submerged internodes of deepwater rice. During partial submergence, internodes of deepwater rice undergo rapid elongation
as a result of ethylene accumulation in the internodal lacunae. In anin vitro experiment using stem sections from deepwater rice, treatment with 5 μL L-1 ethylene promoted stem growth by up to 3.2-foId times over air treatment. Expression patterns were analyzed for genes that
encode GA- and ABA-biosynthesis enzymes to determine any possible molecular basis for the changes observed in GA1 and ABA contents as a result of ethylene action. Expression of theOsGA20ox2 andOsGA20ox4 genes, which encode GA 20-oxidase, and of theOsGA3ox2 gene, which encodes the enzyme that converts GA20 to CA1, was up-regulated, whereas that of three ABA-biosynthetic genes —OsNCED1, OsNCED2, andOsNCEDS-was down-regulated in the presence of ethylene. These results indicate that GA and ABA contribute equally to the submergence-or
ethylene-induced stem elongation of deepwater rice via the coordinated and opposite regulation of biosynthesis. 相似文献
9.
The role of gibberellins (GAs) in the regulation of shoot elongation is well established but the phytohormonal control of
dry-matter production is poorly understood. In the present study, shoot elongation and dry-matter production were resolved
by growing Brassica napus L. seedlings under five light intensities (photon flux densities) ranging from 25 to 500 μmol m−2 s−1. Under low light, plants were tall but produced little dry weight; as light intensity was increased, plants were progressively
shorter but had increasing dry weights. Endogenous GAs in stems of 16- and 17-d-old plants were analyzed by gas chromatography-selected
ion monitoring with [2H2] internal standards. The contents of GAs increased dramatically with decreasing light intensity: GA1, GA3, GA8 and GA20 were 62, 15, 16 and 32 times higher, respectively, under the lowest versus highest light intensities. Gibberellin A19 was not measured at 25 μmol m−2 s−1 but was 9␣times greater in the 75 compared to 500 μmol m−2 s−1 treatment. Shoot and hypocotyl lengths were closely positively correlated with (log) GA concentration (for example: r
2 = 0.93 for GA1 and hypocotyl length) but shoot dry matter was negatively correlated with GA concentration. The application of gibberellic
acid (GA3) produced elongation of plants grown under high light, indication that their low level of endogenous GA was limiting shoot
elongation. Although endogenous GA20 showed the greatest influence of light treatment, metabolism of [3H]GA20 and of [3H]GA1 was only slightly influenced by light intensity, suggesting that neither 2β- nor 3β-hydroxylation were points of metabolic
regulation. The results of this study indicate that GAs control shoot elongation but are not directly involved in the regulation
of shoot dry weight in Brassica. The study also suggests a role of GAs in photomorphogenesis, serving as an intermediate between light condition and shoot
elongation response.
Received: 18 June 1998 / Accepted: 29 July 1998 相似文献
10.
The involvement of gibberellins (GAs) and ethylene in the process of root radial expansion was studied in young seedlings
of Carrizo citrange [Citrus sinensis (L.) Osb. × Poncirus trifoliata (L.) Raf.]. The GA inhibitors cycocel, paclobutrazol, and tetcyclacis enhanced radial expansion of the root tip (up to 2.3-fold)
as a result of increases in stele diameter and inner cortex width. The GA deficiency increased cell number and width, and
changed the polarity of growth, generating wider and shorter cortical cells in the elongation zone. In the presence or absence
of GA inhibitors, GA3 decreased root tip width and reduced all parameters related to radial expansion. The ethylene inhibitors (aminooxyacetic
acid; cobalt ions, CoCl2; silver thiosulfate) suppressed swelling induced by GA deficiency, generating thinner cells just as GA3 did. In contrast to GA3, ethylene inhibitors produced longer cells strongly resembling those of the untreated seedlings. Ethylene released by ethephon
did not modify root tip width in control plants, while root diameter behind the root tip was increased. In the presence of
low and ineffective concentrations of cycocel, the ethylene precursor 1-aminocyclopropane-1-carboxylic acid increased radial
expansion of root tips (1.3-fold) and changed the polarity of growth, producing wider and shorter inner cortical cells as
GA inhibitors did. These observations imply, first, that ethylene is the hormonal effector of the process of root radial expansion
and, second, that the endogenous GAs modulate the promotive response of ethylene.
Received: 4 October 1996 / Accepted: 25 December 1996 相似文献
11.
Relationships between gibberellins and floral initiation were investigated in a conditional non-flowering mutant of red clover, Trifolium pratense. Untreated mutant plants will not flower under long-days, but will do so when certain GAs are applied. Gibberellins, A3, A1, A7, and A5 all resulted in both stem elongation and flowering whilst GA4 produced the elongation only. Applications of GA20, GA8 and GA13 under long-days had no detectable effect. Thus, by combining the use of the mutant with the application of different GAs, the correlation between the processes of stem elongation and floral initiation, which is normally strongly expressed in this species, was broken. Endogenous gibberellins shown to be present in normal plants were also found in the mutant genotype. Gibberellins alone were not sufficient to initiate floral development in the mutant, there being an essential element of interaction with long-days. These results are discussed in relation to the nature of the lesion in the mutant and the signal provided by the applied gibberellin. 相似文献
12.
Sandra Irene Pitta-Alvarez Ana María Giulietti 《In vitro cellular & developmental biology. Plant》1997,33(2):147-153
Summary
Brugmansia candida, an indigenous South American plant, produces the tropane alkaloids scopolamine and hyoscyamine, which are widely employed
in medicine as anticholinergic agents. In this research, hairy roots of Brugmansia candida, obtained through infection with Agrobacterium rhizogenes LBA 9402, were employed to produce these tropane alkaloids in vitro. The effects of different concentrations of GA7 on kinetics of growth and alkaloid accumulation on two different hairy root clones of B. candida were analyzed, and the influence of GA7 on the number of new branches and rates of elongation was also studied. On clone 7A, GA7 at concentrations of 10−4, 10−1, and 1 mg/l increased the exponential growth rate. Levels of 10−1 and 10−4 mg/l GA7 elevated the scopolamine/hyoscyamine (S/H) ratios in the early phases of growth, but the sum of scopolamine plus hyoscyamine
per flask (S + H) decreased during that period. When 1 mg/l GA7 was used, the highest S/H ratios were observed in late exponential/early stationary phases, but the highest S + H totals
were obtained in mid-exponential phase. GA7 at levels of 10−1 and, especially, 1 mg/l exerted a positive effect on formation, emergence, and rate of elongation of lateral roots (clone
7A). On clone 7B, levels of 10−1 and 1 mg/l GA7 did not alter significantly the exponential growth rate. GA7 in concentrations of 10−1 mg/l induced increases in both S/H ratio and S + H totals in late phases of growth. 相似文献
13.
Jose L. Garcia-Martinez Noah Ben-Shalom Lawrence Rappaport 《Plant Growth Regulation》1984,2(3):209-216
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 相似文献
14.
Masayuki Katsumi 《Journal of plant research》1973,86(4):267-273
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. 相似文献
15.
The effect of the application of gibberellins to Tagetes minuta L. achenes (seeds) was determined at both 25°C, the optimal germination temperature, and 35°C, at which temperature the achenes are thermoinhibited. Both GA3 and GA4+7 accelerated germination at 25°C. Seed germination at 25°C was inhibited by paclobutrazol, but on subsequent application of GA4+7 rapid germination was induced. Following application of GA3 or GA4+7 to thermoinhibited seeds, a significantly higher final germination percentage was observed than in the distilled water control. However, endogenous gibberellin levels in germinating and thermoinhibited seeds did not differ significantly. 相似文献
16.
CCC, uniconazol, ancymidol, prohexadione-calcium (BX-112), and CGA 163′935, which represent three groups of gibberellin (GA)
biosynthesis inhibitors, were applied as a soil drench to Sorghum bicolor cultivars 58M (phyB-1, phytochrome B-deficient mutant) and 90M (phyB-2, equivalent phenotypically to wild type, PHYB, except for small differences in flowering dates). The inhibitors that block
steps before GA12 (CCC, uniconazol, and ancymidol) lowered the concentrations of all endogenous early-C13α-hydroxylation pathway GAs found
in sorghum: GA12, GA53, GA44, GA19, GA20, GA1, and GA8. In contrast, the inhibitors that block the conversion of GA20→ GA1, (CGA 163′935 and BX-112) drastically reduced GA1 and GA8 levels, but they either did not change or caused accumulation of intermediates from GA12 to GA20. Combinations of pre-GA12 inhibitors and GA3 plus GA1 strongly reduced GAs other than GA1 and GA3. Each of these compounds inhibited shoot growth in both cultivars and delayed floral initiation in 90M. Floral initiation
of 58M was also delayed by CCC, uniconazol, and ancymidol but not by CGA 163`935 and BX-112. This separation of shoot elongation
from floral initiation in sorghum is novel. Both inhibition of shoot growth and delayed floral initiation were almost completely
relieved by a mixture of GA3 and GA1 in both 58M and 90M. This observation, plus the much lower levels of endogenous GA3 than of GA1 observed in these experiments, implies that GA1 is the major endogenous GA active in shoot elongation. CGA 163′935 and BX-112 also failed to promote tillering in 58M, whereas
inhibitors active before GA12 did so. The possibility that the GA20→ GA1 inhibitors fail to block flowering and promote tillering in 58M because biosynthetic intermediates between GA12 and GA20 accumulate and/or because 58M is altered in GA metabolism in this same region of the biosynthetic pathway is discussed.
Received April 7, 1998; accepted July 31, 1998 相似文献
17.
BA at 10–5
M, GA3 at 3×10–4
M or GA4+7 at 3×10–5
M partially or largely reversed the inhibition of Amaranthus caudatus seed germination due to JA-Me. BA or GA3 did not affect ethylene production and ACC oxidase activity in vivo in the presence of JA-Me before radicle protrusion. However, both increased ethylene production after 72 h of incubation, when the reversal of the JA-Me inhibition of seed germination was observed. AVG at 3×10–4
M decreased ethylene production when it was applied simultaneously with BA and JA-Me or GA3 and JA-Me, but it had no effect on seed germination. NBD almost completely reversed the stimulatory effect of BA, GA3 or GA4+7 on the germination of seeds in the presence of JA-Me. Exogenous ethylene reversed the inhibitory effect of NBD. The results indicate that action of endogenous ethylene is involved in the response of JA-Me inhibited seeds to BA or GAs. 相似文献
18.
Lettuce plants were treated with gibberellic acid (GA3) and uniconazole (UZ; a gibberellin synthesis inhibitor) to investigate the influence of GA3 on cell division frequency in the shoot apical meristem (SAM) during stem elongation and flower initiation in lettuce (Lactuca sativa) grown in a greenhouse. GA3 (0.1 mM) was sprayed on the surface of outer leaves and uniconazole solution (0.86 mM) was applied to the soil. GA3 increased cell division frequency in the peripheral zone and the rib meristem of shoot apices, and this was associated with
the stimulation of stem elongation. UZ treatment decreased cell division frequency in the peripheral zone, rib meristem and
subapical pith, and this was associated with restricted stem elongation. Treatment with UZ and GA3 together induced minor stem elongation. Flower induction occurred 3 d earlier in the GA3 and UZ+GA3 treatments than in the control, while the UZ treatment delayed flower initiation for more than 9 d relative to the control. 相似文献
19.
Effects of the gibberellins A4+7(GA4+7) and A3(GA3), benzyladenine (BA) and forchlorfenuron (CPPU) on deposition of the cuticular membrane (CM) in developing tomato (Lycopersicon esculentum L.) fruit were investigated. Growth regulators were applied when fruit development within trusses ranged from the flower
to the mature stage. Developmental stage of fruit at the time of application was indexed by fruit diameter. Fruit were harvested
at maturity, the CM isolated enzymatically on an individual fruit basis and mass of CM per unit fruit surface area calculated.
In mature fruit, mass of CM per fruit increased with fruit size, but mass of CM per unit surface area was independent of fruit
size, position within a truss and position of the truss on the plant. GA4+7 and GA3 increased CM mass per unit fruit surface area at concentrations up to 300 mg l−1. Young fruit (5–10 mm diam. at time of application) was most responsive. Responsiveness decreased as fruit development at
application progressed towards maturity. There was no consistent effect of GA4+7 or GA3 on fruit mass. BA (up to 100 mg l−1) or CPPU (up to 3 mg l−1) had no significant effect on CM mass per unit surface area regardless of developmental stage. Higher concentrations of BA
or CPPU decreased CM mass per unit surface area. There was no effect of BA or CPPU on fruit mass. Potential mechanisms and
benefits of a gibberellin induced increase in CM deposition are discussed. 相似文献
20.
The role of gibberellins A1 and A3 in fruit growth of Pisum sativum L. and the identification of gibberellins A4 and A7 in young seeds 总被引:2,自引:0,他引:2
Maria J. Rodrigo José L. García-Martínez Cristina M. Santes Paul Gaskin Peter Hedden 《Planta》1997,201(4):446-455
Gibberellins A1 and A3 are the major physiologically active gibberellins (GAs) present in young fruit of pea (Pisum sativum L.). The relative importance of these GAs in controlling fruit growth and their biosynthetic origins were investigated in
cv. Alaska. In addition, the non-13-hydroxylated active GAs, GA4 and GA7, were identified for the first time in young seeds harvested 4 d after anthesis, although they are minor components and are
not expected to play major physiological roles. The GA1 content is maximal in seeds and pods at 6 d after anthesis, the time of highest growth-rate of the pod (Garcia-Martinez et
al. 1991, Planta 184: 53–60), whereas gibberellic acid (GA3), which is present at high levels in seeds 4–8 d after anthesis, has very low abundance in pods. Gibberellins A19, A20 and A29 are most concentrated in seeds at, or shortly after, anthesis and their abundance declines rapidly with development, concomitant
with the sharp increase in GA1 and GA3 content. Application of GA1 or GA3 to the leaf subtending an emasculated flower stimulated parthenocarpic fruit development. Measurement of the GA content of
the pods at 4 d after anthesis indicated that only 0.002–0.5% of the applied GA was transported to the fruit, depending on
dose. There was a linear relationship between GA1 content and pod weight up to about 2 ng · (g FW)−1, whereas no such correlation existed for GA3 content. The concentration of endogenous GA1 in pods from pollinated ovaries is just sufficient to give the maximum growth response. It is concluded that GA1, but not GA3, controls pod growth in pea; GA3 may be involved in early seed development. The distribution of GAs within the seeds at 4 d post anthesis was also investigated.
Most of the GA1, GA8, GA19, GA20 and GA29 was present in the testa, whereas GA3 was distributed equally between testa and endosperm and GA4 was localised mainly in the endosperm. Of the GAs analysed, only GA3 and GA20 were detected in the embryo. Metabolism experiments with intact tissues and cell-free fractions indicated compartmentation
of GA biosynthesis within the seed. Using 14C-labelled GA12, GA9, 2,3-didehydroGA9 and GA20 as substrates, the testa was shown to contain 13-hydroxylase and 20-oxidase activities, the endosperm, 3β-hydroxylase and
20-oxidase activities. Both tissues also produced 16,17-dihydrodiols. However, GA1 and GA3 were not obtained as products and it is unlikely that they are formed via the early 13-hydroxylation pathway. [14C]gibberellin A12, applied to the inside surface of pods in situ, was metabolised to GA19, GA20, GA29, GA29-catabolite, GA81 and GA97, but GA1 was not detected. Gibberellin A20 was metabolised by this tissue to GA29 and GA29-catabolite.
Received: 23 July 1996 / Accepted: 2 September 1996 相似文献