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1.
Grete Grindal Arild Ernstsen James B. Reid Olavi Junttila Bente Lindgård Roar Moe 《Physiologia plantarum》1998,102(4):523-531
Gibberellin (GA) is believed to be involved in thermoperiodic stem elongation. With this in mind, we studied the correlation between gibberellin A1 (GA1) levels and stem elongation affected by alternating day (DT) and night temperature (NT) in 5 genotypes of Pisum sativum differing in their degree of dwarfism. The endogenous GA content in the tissue of two of the genotypes was determined by combined gas chromatography and mass spectrometry. The wild genotype developed 40 to 50% shorter stems and internodes under a low DT and high NT combination (negative difference [DIF] between DT and NT, DT/NT 15.5/21.5 or 14/24°C) than under the opposite regime of high DT and low NT (positive DIF, DT/NT 22.5/16.5 or 24/14°C). The GA biosynthetic mutants ls and le, and the auxin and brassinosteroid mutant lkb responded in a similar way, but not as strongly as the wild type. The stem length of the GA-insensitive slender mutant (la crys) was reduced by only 8% under negative compared to positive DIF. In the wild type endogenous GA levels decreased by 60% from positive to negative DIF in the upper part of the stem. Further, there was a corresponding decrease in the levels of precursors to GA1, i.e. GA53, GA44, GA19 and GA20, while 2β-hydroxylated GA20 and GA1, GA29 and GA8, respectively, were unaffected by DIF. A similar increase in the ratios of GA29 to GA20 and GA8 to GA1 from positive to negative DIF was seen in the stem tissue of the le mutant as in the wild type. The temperature regimes affected the levels of GA1 and its precursors in combined leaf and petiole samples and in the shoot tip in a similar manner as in the stem tissue. However, the different temperature regimes did not affect the ratio of GA8/GA1 in the shoot tip. The results indicate that altered stem elongation of the pea plants in response to diurnal temperature alternations may be mediated by changes in endogenous levels of GA1. The GA1 levels may be controlled by an effect of DIF on both biosynthetic and inactivation steps. 相似文献
2.
The effects of thermo- and photoperiodicity on elongation growth and on endogenous level of gibberellins (GAs) in Begonia x hiemalis during various phases of the day-night cycle have been studied. Plant tissue was harvested during the day and night cycle
after temperature and photoperiodic treatments and analyzed for endogenous GAs using combined gas chromatography and mass
spectrometry. Elongation growth increased when the difference between day and night temperature (DIF = DT − NT) increased
from a negative value (−9.0 and −4.5°C) to zero and with increasing photoperiod from 8 to 16 h. When applied to the youngest
apical leaf, gibberellins A1, A4, and A9 increased the elongation of internodes and petioles. GA4 had a stronger effect on elongation growth than GA1 and GA9. In relative values, the effect of these GAs decreased when DIF increased from −9 to 0°C. The time of applying the GAs during
a day and night cycle had no effect on the growth responses. In general, endogenous levels of GA19 and GA20 were higher under negative DIF compared with zero DIF. The level of endogenous GA1 in short day (SD)-grown plants was higher under zero DIF than under negative DIF, but this relationship did not appear in
long day (LD)-grown plants. The main effects of photoperiod seem to be a higher level of GA19 and GA1 at SD compared with LD, whereas GA20 and GA9 show the opposite response to photoperiod. No significant differences in endogenous level of GA1, GA9, GA19, and GA20 were found for various time points during the diurnal day and night cycle. Endogenous GA20 was higher in petiole and leaf compared with stem, whereas there were no differences of GA1, GA9, and GA19 between plant parts. No clear relationship was found between elongation of internodes and petioles and levels of endogenous
GAs.
Received December 26 1996; accepted July 1, 1997 相似文献
3.
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
4.
The objective of this work was to study the role of the phytochromes (phy) B, D and E in the thermoperiodic control of elongation
and flowering time in Arabidopsis thaliana. WT, and phyB, phyD and phyE single mutants, and phyB phyD and phyB phyE double mutants, were grown under day/night temperatures (DT/NT) of 12/22°C, 17/17°C or 22/12°C (negative, zero and positive
DIF, respectively) for inflorescence stem length measurements, and under DT/NT 17/25°C or 25/17°C (negative and positive DIF,
respectively) for leaf morphology and flowering time measurements. In WT final length of the stem, petiole and leaf blade
were longer under positive DIF compared to negative DIF. The temperature effect was stronger in the leaf petiole than the
stem, whereas only a slight change was seen in the leaf blade length direction and none in the width direction. The temperature
effect on stem and petiole elongation was reduced or nearly eliminated in the genotypes lacking phyB, while a phyD or a phyE mutation had no influence or a slightly positive influence on the temperature effect, respectively. These results suggest
that phyB, and not phyD or phyE, is needed for a complete thermoperiodic control of elongation growth in A. thaliana. For all genotypes tested, plants flowered earlier at negative DIF than positive DIF, suggesting that none of the three phytochromes
B, D, or E is needed for a thermoperiodic control of flowering time in A. thaliana. 相似文献
5.
Effects of Auxin Transport Inhibitors on Gibberellins in Pea 总被引:5,自引:0,他引:5
J. J. Ross 《Journal of Plant Growth Regulation》1998,17(3):141-146
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
6.
The aim of this study was to investigate the role of plant hormones, particularly the gibberellins (GAs), in the thermoperiodic regulation of stem elongation in the short day plant (SDP) Begonia x hiemalis. Effects of GAs and some GA precursors were tested on plants grown under alternating day/night temperatures (DT/NT; 12/12 h), and the effects of these temperature regimes on endogenous plant hormones were analyzed using combined gas chromatography and mass spectrometry (GC-MS).Compared with constant temperatures (19/19 °C; 21/21 °C), stem elongation was significantly inhibited by low DT/high NT (14/24 °C; 18/24 °C) and enhanced by the opposite treatments (24/14 °C; 26/17 °C). GA1 stimulated elongation of internodes and petioles while ent-kaurene, kaurenoic acid, GA12, GA19, GA20 had no significant effect. The effect of GA1 was enhanced by a simultaneous application of calcium 3,5-dioxo-4-propionylcyclohexanecarboxylate (BX-112). BX-112 inhibited internode elongation at high DT/low NT (24/14 °C) but not at the reverse temperature regime.Gibberellins A53, A19, A20, A1, A4, A9, and indoleacetic acid (IAA), were identified by GC-MS from both leaves, including the petioles, and stems of B. x hiemalis. There were no apparent relationships between elongation of internodes and petioles and endogenous contents of gibberellins A53, A19, A20, and A1. Recoveries of deuterated GA4 and GA9 were generally too low for estimation of endogenous levels of these GAs.Constant temperature resulted in more open flowers and flower buds compared to alternating DT and NT. BX-112 decreased the time to anthesis. 相似文献
7.
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
8.
Lilium tongiflorum Thunb. cv. Nellie White plantswere grown in different day/night temperature (DT/NT) environmentsto determine the anatomical basis for differential responsesof stem elongation to DT and NT. Lilium plants were forced in1986 and 1987 under 25 and 12 different DT/NT environments,respectively, with temperatures ranging from 14 to 30 °C.Parenchyma and epidermal cell length and width were measuredin stem tissue (1987) and epidermal cell length and width weremeasured in leaf tissue (1986). Total cell number per internodeand vertical cell number per internode were calculated. Stemparenchyma and stem and leaf epidermal cell length increasedlinearly as the difference (DIF) between DT and NT increased(DIF = DT - NT), i.e. as DT increased relative to NT.DIF had no effect on stem parenchyma width, stem and leaf epidermalcell width, or cell number per internode. Data suggested thatstem elongation responses to DIF are elicited primarily througheffects on cell elongation and not division. Key words: Thermoperiodism, thermomorphogenesis, stem elongation, DIF, cell division, cell elongation, leaf expansion 相似文献
9.
K. R. Foster I.-j. Lee R. P. Pharis P. W. Morgan 《Journal of Plant Growth Regulation》1997,16(2):79-87
Plants of early flowering mutant and wild type genotypes of Sorghum bicolor were treated with ring D-modified gibberellins (GAs), and the effects on endogenous GA levels were determined. The growth
and timing of floral initiation in 58M plants grown under 18-h days (which significantly delays floral initiation in this
short day plant) following treatment with these compounds, relative to GA3 and GA5 treatments, were also investigated. Application of the endo-isomer of C16,17-dihydro-GA5 (endo-DiHGA5), the exo-isomer of C16,17-dihydro-GA5 (exo-DiHGA5), and C16α,17-dichloromethanodihydro-GA5 (DMDGA5) altered GA levels in both genotypes. Each ring D-modified GA significantly inhibited shoot growth while significantly decreasing
levels of GA1 and increasing levels of its immediate precursor, GA20. Gibberellin A8 levels also decreased. Tillering was not affected by any treatment. For the early flowering genotype 58M, grown under noninductive
long days, both dihydro-GA5 isomers promoted floral initiation while shoot growth was strongly inhibited, and floral development was strongly advanced
beyond floral stage 4. Gibberellin A3 and GA5, applied under the same conditions, promoted shoot growth slightly and gave ``floral-like' apical meristems that did not
develop past floral stage 1. These results suggest that the reduced shoot growth of sorghum, which follows application of
those ring D-modified GAs, is due to their inhibiting the 3β hydroxylation of GA20 to GA1, thereby reducing the GA1 content. That floral initiation was hastened and floral development promoted in genotype 58M by application of both isomers
of DiHGA5 are in contrast to the effects of other GA biosynthesis inhibitors, which act earlier in the GA biosynthesis pathway, but
are consistent with results seen for long day grasses. This suggests that endo-DiHGA5 and exo-DiHGA5 may be acting directly in promoting floral initiation and subsequent floral apex development of this short day plant under
long day conditions.
Received October 3, 1996; accepted January 22, 1997 相似文献
10.
Day and night temperature responses in Arabidopsis: effects on gibberellin and auxin content,cell size,morphology and flowering time 总被引:1,自引:0,他引:1
The effect of 16 different day (DT) and night (NT) temperature combinations (DT and NT 12, 17, 22 and 27 degrees C) on rosette leaf growth, flower stem elongation and flowering time in Arabidopsis thaliana Ler was investigated. Final leaf length decreased with increasing NT due to a combination of reduced elongation period and reduced elongation rate. Final stem length increased with increasing DT due to increased elongation rate, and decreased with increasing NT due to a decrease in elongation period. Under NT 27 degrees C, however, stem elongation rate increased greatly, resulting in the same final stem length as under NT 12 degrees C. The transition to flowering was accelerated by increasing NT. A linear regression analysis was performed to clarify the relationship between final leaf length, final stem length and flowering time with DIF (DT minus NT) and/or ADT (average daily temperature). For all three variables, the effect of DIF depended on ADT and vice versa. The relationship of final stem length with DIF also depended on the temperature range. Increased cell volume in flower stems developing at DT/NT 22/12 degrees C gave rise to longer and thicker stems compared with stems developing at DT/NT 12/22 degrees C. GC-MS analysis (gas chromatography-mass spectrometry) showed that the endogenous level of IAA was 56 % higher in stems grown under DT/NT 22/12 degrees C compared with DT/NT 12/22 degrees C. Of the 12 gibberellins analysed, however, only the level of non-bioactive GA29 was affected by the temperature treatment. 相似文献
11.
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
12.
Effect of Day and Night Temperature on Internode and Stem Length in Chrysanthemum: Is Everything Explained by DIF? 总被引:2,自引:0,他引:2
In many plant species, including chrysanthemum, a strong positive correlation between internode length and DIF [difference between day (DT) and night (NT) temperature] has been observed. However, Langton and Cockshull (1997. Scientia Horticulturae 69: 229-237) reported no such relationship and showed that absolute DT and NT explained internode length rather than DIF. To investigate these conflicting results and to clarify the validity of the DIF concept, cut chrysanthemums (Chrysanthemum 'Reagan Improved') were grown in growth chambers at all 16 combinations of four DT and four NT (16, 20, 24 and 28 degrees C) with a 12 h day length. Length of internode 10, number of internodes and stem length were measured on days 5, 10, 17, 22 and 27 after starting the temperature treatments. Internode length on day 10 showed a positive linear relationship with DIF (R2 = 0.64). However, when internodes had reached their final length in all treatments (day 27), a much stronger positive linear relation was observed (R2 = 0.81). A model to predict final internode length was developed based on the absolute DT and NT responses: both responses were optimum curves and no significant interaction between DT and NT occurred [final internode length (mm) = -32.23 + 3.56DT + 1.08NT - 0.0687DT2 - 0.0371NT2; R2 = 0.91, where TD is day temperature and TN is night temperature]. It is shown that DIF can predict final internode length only within a temperature range where effects of DT and NT are equal in magnitude and opposite in sign (18-24 degrees C). Internode appearance rate, as well as stem length formed during the experiment, showed an optimum response to DT. 相似文献
13.
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
14.
Paclobutrazol [(2RS,3RS)-1-(4-chlorophenyl)methyl-4,4-dimethyl-2-(1h-1,2,4-trizol-1-yl)penten-3-ol] effectively decreased vegetative growth of rice
(Oryza sativa L.) seedlings and increased the chlorophyll content. The number of veins in a leaf, the calculated number of stomata per
leaf, and the length of guard cells were not altered by the paclobutrazol treatment, suggesting an effect on cell elongation.
The allocation pattern of carbohydrates was changed by either gibberellin (GA) or paclobutrazol treatment. GA3 induced more shoot growth and less accumulation of starch than the control and paclobutrazol-treated seedlings. Photosynthetic
ability was not affected by either paclobutrazol or GA3 treatment. Paclobutrazol-treated plants allocated a smaller amount of photosynthates for vegetative shoot growth and stored
more as starch in the crowns than the control and GA3-treated plants. The same starch degrading activity in the crown tissue of paclobutrazol-treated seedlings as in control plants
suggests that the accumulated starch is utilized in a normal activity for growth including leaf emergence, tiller formation,
and root production, resulting in improved seedling quality.
Received May 30, 1996; accepted December 10, 1996 相似文献
15.
The brassinosteroid growth response in pea is not mediated by changes in gibberellin content 总被引:4,自引:0,他引:4
The objective of this study was to increase our understanding of the relationship between brassinosteroids (BRs) and gibberellins (GAs) by examining the effects of BR deficiency on the GA biosynthesis pathway in several tissue types of pea (Pisum sativum L.). It was suggested recently that, in Arabidopsis, BRs act as positive regulators of GA 20-oxidation, a key step in GA biosynthesis [Bouquin et al. (2001) Plant Physiol 127:450–458]. However, this may not be the case in pea as GA20 levels were consistently higher in all shoot tissues of BR-deficient (lk and lkb) and BR-response (lka) mutants. The application of brassinolide (BL) to lkb plants reduced GA20 levels, and metabolism studies revealed a reduced conversion of GA19 to GA20 in epi-BL-treated lkb plants. These results indicate that BRs actually negatively regulate GA20 levels in pea. Although GA20 levels are affected by BR levels, this does not result in consistent changes in the level of the bioactive GA, GA1. Therefore, even though a clear interaction exists between endogenous BR levels and the level of GA20, this interaction may not be biologically significant. In addition to the effect of BRs on GA levels, the effect of altered GA1 levels on endogenous BR levels was examined. There was no significant difference in BR levels between the GA mutants and the wild type (wt), indicating that altered GA1 levels have no effect on BR levels in pea. It appears that the BR growth response is not mediated by changes in bioactive GA levels, thus providing further evidence that BRs are important regulators of stem elongation. 相似文献
16.
Third internodes or whole stems of 7-days old etiolated pea plants were extracted and the content of gibberellin-like substances and inhibitors has been determined. Extracts were found to contain four or five different gibberellin-like substances, some of which are chromatographically similar to GA3. The content of gibberellins has been high in young internodes and decreased along with the internodes elongation. Brief red light irradiation brings about quantitative changes in gibberellin content, depending also on the length of internodes. The extracts contain acidic and neutral inhibitors which interfere with the response to GA3. The content of the inhibitors does not seem to be affected by the ageing of internodes or by the light treatment. 相似文献
17.
Thermoperiodic stem elongation involves transcriptional regulation of gibberellin deactivation in pea 总被引:3,自引:0,他引:3
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The physiological basis of thermoperiodic stem elongation is as yet poorly understood. Thermoperiodic control of gibberellin (GA) metabolism has been suggested as an underlying mechanism. We have investigated the influence of different day and night temperature combinations on GA levels, and diurnal steady-state expression of genes involved in GA biosynthesis (LS, LH, NA, PSGA20ox1, and PsGA3ox1) and GA deactivation (PsGA2ox1 and PsGA2ox2), and related this to diurnal stem elongation in pea (Pisum sativum L. cv Torsdag). The plants were grown under a 12-h light period with an average temperature of 17 degrees C. A day temperature/night temperature combination of 13 degrees C/21 degrees C reduced stem elongation after 12 d by 30% as compared to 21 degrees C/13 degrees C. This was correlated with a 55% reduction of GA1. Although plant height correlated with GA1 content, there was no correlation between diurnal growth rhythms and GA1 content. NA, PsGA20ox1, and PsGA2ox2 showed diurnal rhythms of expression. PsGA2ox2 was up-regulated in 13 degrees C/21 degrees C (compared to 21 degrees C/13 degrees C), at certain time points, by up to 19-fold. Relative to PsGA2ox2, the expression of LS, LH, NA, PSGA20ox1, PsGA3ox1, and PsGA2ox1 was not or only slightly affected by the different temperature treatments. The sln mutant having a nonfunctional PsGA2ox1 gene product showed the same relative stem elongation response to temperature as the wild type. This supports the importance of PsGA2ox2 in mediating thermoperiodic stem elongation responses in pea. We present evidence for an important role of GA catabolism in thermoperiodic effect on stem elongation and conclude that PsGA2ox2 is the main mediator of this effect in pea. 相似文献
18.
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
19.
Summary Seedlings of Scrophularia marilandica were grown at different combinations of day/night temperature and photoperiod under controlled conditions. The species flowered in long days. The stems of plants grown at low temperature and short photoperiod failed to elongate. Treatment with gibberellic acid (GA3) simulated the effect of increasing temperature and photoperiod and caused stem elongation in plants which would otherwise not have elongated. Application of GA3 to plants grown at high temperature and long photoperiod resulted in increased stem elongation and flowering. The growth retardant (2-chloroethyl)trimethylammonium chloride (CCC) had little effect on rosette plants grown at low temperature and short photoperiod. Application of CCC to +GA3 plants grown at a higher temperature and long photoperiod gave a significant increase in stem height. The interaction between temperature and applied GA is described in an experiment using plants grown at high and low temperatures for varying periods of time.This work was supported by National Science Foundation Grant GB 17483. 相似文献
20.
CCC-Induced increase of gibberellin levels in pea seedlings 总被引:1,自引:1,他引:0
Summary Pea seedlings (cv. Alaska), were treated with two concentrations of (2-chloroethyl)trimethylammonium chloride (CCC) and choline chloride. Treatment with 1 mg/l CCC resulted in as much as a 150fold increase in endogenous gibberellin (GA) levels without there being any parallel stimulation of growth. Plants grown in 1,000 mg/l CCC were severely dwarfed but contained GA levels not significantly different from control plants grown in distilled water. CCC also retarded GA3-induced growth of pea seedlings. These effects appear to be CCC specific as the CCC analogue choline chloride affected neither the GA content of pea seedlings nor their response to GA3. The lack of correlation between endogenous GA levels and stem height suggests that in peas the predominant factor in CCC-induced inhibition of stem growth is not related to an effect of CCC on GA biosynthesis.Supported by National Research Council (Canada) grant A-5727.Supported by a Postdoctoral Fellowship from NRC Grant A-2585 to R.P. Pharis. 相似文献