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1.
Regulation of sucrose and starch metabolism in potato tubers in response to short-term water deficit 总被引:24,自引:0,他引:24
Peter Geigenberger Ralph Reimholz Michael Geiger Lucia Merlo Vittoria Canale Mark Stitt 《Planta》1997,201(4):502-518
To investigate the effect of water stress on carbon metabolism in growing potato tubers (Solanum tuberosum L.), freshly cut and washed discs were incubated in a range of mannitol concentrations corresponding to external water potential
between 0 and −1.2 MPa. (i) Incorporation of [14C]glucose into starch was inhibited in water-stressed discs, and labeling of sucrose was increased. High glucose overrode
the changes at low water stress (up to −0.5 MPa) but not at high water stress. (ii) Although [14C]sucrose uptake increased in water-stressed discs, less of the absorbed [14C]sucrose was metabolised. (iii) Analysis of the sucrose content of the discs confirmed that increasing water deficit leads
to a switch, from net sucrose degradation to net sucrose synthesis. (iv) In parallel incubations containing identical concentrations
of sugars but differing in which sugar was labeled, degradation of [14C]sucrose and labeling of sucrose from [14C]glucose and fructose was found at each mannitol concentration. This shows that there is a cycle of sucrose degradation and
resynthesis in these tuber discs. Increasing the extent of water stress changed the relation between sucrose breakdown and
sucrose synthesis, in favour of synthesis. (v) Analysis of metabolites showed a biphasic response to increasing water deficit.
Moderate water stress (0–200 mM mannitol) led to a decrease of the phosphorylated intermediates, especially 3-phosphoglycerate
(3PGA). The decrease of metabolites at moderate water stress was not seen when high concentrations of glucose were supplied
to the discs. More extreme water stress (300–500 mM mannitol) was accompanied by an accumulation of metabolites at low and
high glucose. (vi) Moderate water stress led to an activation of sucrose phosphate synthase (SPS) in discs, and in intact
tubers. The stimulation involved a change in the kinetic properties of SPS, and was blocked␣by protein phosphatase inhibitors.
(vii) The amount of ADP-glucose (ADPGlc) decreased when discs were incubated on 100 or 200 mM mannitol. There was a strong
correlation between the in vivo levels of ADPGlc and 3PGA when discs were subjected to moderate water stress, and when the
sugar supply was varied. (viii) The level of ADPGlc increased and starch synthesis was further inhibited when discs were incubated
in 300–500 mM mannitol. (ix) It is proposed that moderate water stress leads to an activation of SPS and stimulates sucrose
synthesis. The resulting decline of 3PGA leads to a partial inhibition of ADP-glucose pyrophosphorylase and starch synthesis.
More-extreme water stress leads to a further alteration of partitioning, because it inhibits the activities of one or more
of the enzymes involved in the terminal reactions of starch synthesis.
Received: 26 August 1996 / Accepted: 5 November 1996 相似文献
2.
The conservation of desirable properties in foods and ingredients is often based on the maintenance of the amorphous metastable
properties of the systems. Enzymes may be stabilized by drying in saccharide matrices, but a second excipient is generally
required to improve sugar protective effects. The effect of electrolytes on the thermophysical properties of sugar systems
is of special interest because of their major influence on water structure and their possible interactions with biomolecules.
Salts affect the kinetics of very important changes in sugar systems such as crystallization. The purpose of the present work
was to analyze fungal β-galactosidase stability in supercooled systems of trehalose-containing electrolytes (water soluble
acetates, citrates, and chlorides of magnesium and potassium). The degree of sugar crystallization was also related to enzyme
stability. Potassium citrate and acetate improved enzyme stability during freeze-drying and thermal treatment of samples at
water activity (a
w) of 0.22. However, trehalose crystallization inhibition at a
w = 0.43 (which was about 50–60%, related to the system without salt) impaired enzyme protection. Certain salts may act retarding
sugar crystallization, but in the presence of salts, trehalose crystallization is even more critical because the enzyme is
confined in a highly salt-concentrated region. Thus, crystallization inhibition by sugar–salt combinations should be carefully
conducted.
Santagapita, Research Fellow, CONICET, Argentina.
Buera, Member of CONICET, Argentina.
An erratum to this article can be found at 相似文献
3.
In this methods paper, one-dimensional moisture penetration into thin films of sugar glass exposed to different relative humidity
was measured by use of FT-near infrared microspectroscopy working in a spectrum range of wavelength from 1.35 to 2.50 μm.
The peak height ratio of characteristic peaks for H—OH (primarily water) and O—H (primarily sugar) bands, respectively, were
highly correlated to moisture content for both sucrose and lactose systems and were used for calibration of moisture content.
Moisture content along one-dimensional locations was accurately measured using microscopic mapping. Sorption penetration profiles
of moisture content vs. penetration depth were obtained. Depending on the sorption time and storage conditions, moisture penetration
profiles typically showed a fairly sharp boundary between intact glass in the interior and a high moisture content surface
layer, which slowly moved into the sample interior over time. Crystallization was observed to occur at the surface under certain
conditions when insufficient inhibitors were present. In these cases, a moisture peak was seen to penetrate into the glass.
Microspectroscopic mapping proved to be an excellent technique for studying moisture penetration behavior and kinetics, providing
quantitative data for future diffusion modeling.
Support source: NIRCGP grant from USDA. 相似文献
4.
M. Schnuch H. Seebauer 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1998,182(6):767-775
Receptor cell responses in the largest labellar (LL) and tarsal (D) taste hairs of the housefly Musca domestica were investigated electrophysiologically using the tip-recording technique. In LL hairs, test series with lactose in concentrations
of 12.5–400 mmol · l−1 yielded a threshold concentration around 12 mmol · l−1 and a calculated concentration eliciting half-maximal response of around 40 mmol · l−1, the maximal response varying between 18 and 30 impulses/300 ms. D hairs are more sensitive towards lactose, indicated by
a slightly lower threshold and a by 60% higher response to 400 mmol · l−1 lactose. The high variation in the relative stimulating effectiveness of lactose and sucrose and experiments with sugar mixtures
imply that these sugars bind to different receptor sites without noticeable cross affinity. A comparison of the concentration
response characteristics for sucrose and lactose in LL and D hairs suggests that sucrose can combine with more than one site
type, expressed in different proportions in both hair types. Results obtained with p-nitrophenyl-β-galactoside as stimulus indicate that a β-galactoside link is not sufficient for a substance to interact specifically
with the lactose binding site. The exceptional lactose sensitivity of the sugar cell in M. domestica is discussed in the context of food acquirement and digestion.
Accepted: 14 November 1997 相似文献
5.
Migration and reproduction of the Caspian Lamprey, Caspiomyzon wagneri, in the Shirud River were investigated during late-March to early-May at water temperatures ranging from 11 to 21.25°C. We
examined the effect of water temperature on timing of spawning migrations. There was a significant negative relationship between
temperature and intensive migration of Caspian Lamprey (p < 0.05). The most intensive migration of lampreys was at night (21:00–3:00 h) and when the water temperatures averaged 16°C
(34.43%). The overall sex ratio (male to female) was 1.07 to 1. The individual absolute fecundity was 31 ‘758–51’ 198 eggs
(mean±SD—41,924 ± 5,382). The egg diameter was 0.780–1.151 (0.92 ± 0.081) mm. The individual relative fecundity varies from
80.3 to 148.1 (107.2 ± 15.1) eggs per 1 mm of length and from 260.8 to 677.4 (397.6 ± 93) eggs per 1 g of weight. The gonadosomatic
index (GSI) of females was 5.83–31.44 (11.22 ± 4.30). 相似文献
6.
H. Dominguez M. Cocaign-Bousquet N. D. Lindley 《Applied microbiology and biotechnology》1997,47(5):600-603
Growth of Corynebacterium glutamicum on mixtures of glucose and fructose leads to simultaneous consumption of both sugars in which the uptake of each sugar is
directly related to the expression of the corresponding sugar uptake mechanism. The overall rate of sugar uptake was higher
on sugar mixtures than on either glucose or fructose alone and was similar to that observed during sucrose metabolism. The
results suggest that sugar uptake limits metabolic rates though, in the case of fructose, overflow metabolism of both lactate
and dihydroxyacetone was observed. Such products could reflect a higher flux through glycolysis rather than the pentose pathway
during catabolism of fructose.
Received: 24 October 1996 / Received revision: 10 January 1997 / Accepted: 10 January 1997 相似文献
7.
J. Dynesen H. P. Smits L. Olsson J. Nielsen 《Applied microbiology and biotechnology》1998,50(5):579-582
When Saccharomyces cerevisiae are grown on a mixture of glucose and another fermentable sugar such as sucrose, maltose or galactose, the metabolism is
diauxic, i.e. glucose is metabolized first, whereas the other sugars are metabolized when glucose is exhausted. This phenomenon
is a consequence of glucose repression, or more generally, catabolite repression. Besides glucose, the hexoses fructose and
mannose are generally also believed to trigger catabolite repression. In this study, batch fermentations of S. cerevisiae in mixtures of sucrose and either glucose, fructose or mannose were performed. It was found that the utilization of sucrose
is inhibited by concentrations of either glucose or fructose higher than 5 g/l, and thus that glucose and fructose are equally
capable of exerting catabolite repression. However, sucrose was found to be hydrolyzed to glucose and fructose, even when
the mannose concentration was as high as 17 g/l, indicating, that mannose is not a repressing sugar. It is suggested that
the capability to trigger catabolite repression is connected to hexokinase PII, which is involved in the in vivo phosphorylation
of glucose and fructose.
Received: 5 May 1998 / Received revision: 3 August 1998 / Accepted: 8 August 1998 相似文献
8.
A. Krastanov 《Applied microbiology and biotechnology》1997,47(5):476-481
A novel immobilized biocatalyst with invertase activity was prepared by adhesion of yeast cells to wool using glutaraldehyde.
Yeast cells could be immobilized onto wool by treating either the yeast cells or wool or both with glutaraldehyde. Immobilized
cells were not desorbed by washing with 1 M KCl or 0.1 M buffers, pH 3.5–7.5. The biocatalyst shows a maximum enzyme activity
when immobilized at pH 4.2–4.6 and 7.5–8.0. The immobilized biocatalyst was tested in a tubular fixed-bed reactor to investigate
its possible application for continuous full-scale sucrose hydrolysis. The influence of temperature, sugar concentration and
flow rate on the productivity of the reactor and on the specific productivity of the biocatalyst was studied. The system demonstrates
a very good productivity at a temperature of 70 °C and a sugar concentration of 2.0 M. The increase of the volume of the biocatalyst
layer exponentially increases the productivity. The productivity of the immobilized biocatalyst decreases no more than 50%
during 60 days of continuous work at 70 °C and 2.0 M sucrose, but during the first 30 days it remains constant. The cumulative
biocatalyst productivity for 60 days was 4.8 × 103kg inverted sucrose/kg biocatalyst. The biocatalyst was proved to be fully capable of continuous sucrose hydrolysis in fixed-bed
reactors.
Received: 8 November 1996 / Received revision: 31 January 1997 / Accepted: 31 January 1997 相似文献
9.
Water stress stimulates sucrose synthesis and inhibits starch and cell-wall synthesis in tissue slices of growing potato
(Solanum tuberosum L. cv. Desirée) tubers. Based on the analysis of fluxes and metabolites, Geigenberger et al. (1997, Planta 201: 502–518)
proposed that water deficits up to −0.72 MPa stimulate sucrose synthesis, leading to decreased starch synthesis as a result
of the resulting decline of phosphorylated metabolite levels, whereas more-severe water deficits directly inhibit the use
of ADP-glucose. Potato plants with decreased expression of adenosine 5′-diphosphoglucose pyrophosphorylase (AGPase) have been
used to test the prediction that the contribution of AGPase to the control of starch synthesis should decrease in severely
water-stressed tuber material. Freshly cut slices from wild-type and antisense tubers were incubated at a range of mannitol
concentrations (20, 300 and 500 mM) and the metabolism of [14C]glucose was analysed. A 86–97% reduction of AGPase activity led to a major but non-stoichiometric inhibition of starch accumulation
in intact growing tubers attached to the plant (40–85%), and an inhibition of starch synthesis in non-stressed tuber slices
incubated in 20 mM mannitol (60–80%). The inhibition of starch synthesis was accompanied by a 2- to 8-fold increase in the
levels of sugars in intact tubers and a 2- to 3-fold stimulation of sucrose synthesis in tuber slices, whereas respiration
and cell-wall synthesis were not significantly affected. The strong impact of AGPase on carbon partitioning in non-stressed
tubers and tuber slices was retained in slices subjected to moderate water deficit (300 mM mannitol, corresponding to −0.72 MPa).
In discs incubated in 500 mM mannitol (corresponding to −1.2 MPa) this response was modified. A 80–97% reduction of AGPase
resulted in only a 0–40% inhibition of starch synthesis. Further, the water stress-induced stimulation of sucrose synthesis
was abolished in the transformants. The results provide direct evidence that the contribution of AGPase to the control of
starch synthesis can be modified by environmental factors, leading to a lower degree of control during severe water deficits.
There was also a dramatic decrease in the labelling of cell-wall components in wild-type tuber slices incubated with 300 or
500 mM mannitol. The water stress-induced inhibition of cell-wall synthesis occurred independently of AGPase expression and
the accompanying changes in starch and sucrose metabolism, indicating a direct inhibition of cell-wall synthesis in response
to water stress.
Received: 24 February 1999 / Accepted: 28 May 1999 相似文献
10.
Bacterial degradation of pyridine, indole, quinoline, and their derivatives under different redox conditions 总被引:24,自引:0,他引:24
S. Fetzner 《Applied microbiology and biotechnology》1998,49(3):237-250
Bacteria have evolved a diverse potential to transform and even mineralize numerous organic compounds of both natural and
xenobiotic origin. This article describes the occurrence of N-heteroaromatic compounds and presents a review of the bacterial
degradation of pyridine and its derivatives, indole, isoquinoline, and quinoline and its derivatives. The bacterial metabolism
of these compounds under different redox conditions – by aerobic, nitrate-reducing, sulfate-reducing and methanogenic bacteria
– is discussed. However, in natural habitats, various environmental factors, such as sorption phenomena, also influence bacterial
conversion processes. Thus, both laboratory and field studies are necessary to aid our understanding of biodegradation in
natural ecosystems and assist the development of strategies for bioremediation of polluted sites. Occurring predominantly
near (former) wood-treatment facilities, creosote is a frequent contaminant of soil, subsoil, groundwater, and aquifer sediments.
In situ as well as withdrawal-and-treatment techniques have been designed to remediate such sites, which are polluted with
complex mixtures of aromatic and heterocyclic compounds.
Received: 26 September 1997 / Received revision: 23 December 1997 / Accepted: 27 December 1997 相似文献
11.
Trehalose and sucrose, two sugars that are involved in the protection of living organisms under extreme conditions, and their mixtures with salts were employed to prepare supercooled or freeze-dried glassy systems. The objective of the present work was to explore the effects of different salts on water sorption, glass transition temperature (T(g)), and formation and melting of ice in aqueous sugar systems. In the sugar-salt mixtures, water adsorption was higher than expected on the basis of the water uptake by each pure component. In systems with a reduced mass fraction of water (w less-than-or-equal 0.4), salts delayed water crystallization, probably due to ion-water interactions. In systems where > 0.6, water crystallization could be explained by the known colligative properties of the solutes. The glass transition temperature of the maximally concentrated matrix (T(g)') was decreased by the presence of salts. However, the actual T(g) values of the systems were not modified. Thus, the effect of salts on sorption behavior and formation of ice may reflect dynamic water-salt-sugar interactions which take place at a molecular level and are related to the charge/mass ratio of the cation present without affecting supramolecular or macroscopic properties. 相似文献
12.
Summary. This study examined 10 wks of resistance training and the ingestion of supplemental protein and amino acids on muscle performance
and markers of muscle anabolism. Nineteen untrained males were randomly assigned to supplement groups containing either 20 g
protein (14 g whey and casein protein, 6 g free amino acids) or 20 g dextrose placebo ingested 1 h before and after exercise
for a total of 40 g/d. Participants exercised 4 times/wk using 3 sets of 6–8 repetitions at 85–90% of the one repetition maximum.
Data were analyzed with two-way ANOVA (p < 0.05). The protein supplement resulted in greater increases in total body mass, fat-free mass, thigh mass, muscle strength,
serum IGF-1, IGF-1 mRNA, MHC I and IIa expression, and myofibrillar protein. Ten-wks of resistance training with 20 g protein
and amino acids ingested 1 h before and after exercise is more effective than carbohydrate placebo in up-regulating markers
of muscle protein synthesis and anabolism along with subsequent improvements in muscle performance. 相似文献
13.
T Roukas 《Journal of industrial microbiology & biotechnology》1999,22(6):617-621
Aureobasidium pullulans P56 was investigated using an adaptation technique and a mixed culture system. The adaptation of A. pullulans and the mixed cultures of A. pullulans and/or Lactobacillus brevisX20, Debaryomyces hansenii 194 and Aspergillus niger did not increase the production of polysaccharide. Enzymic hydrolysis of lactose in deproteinized whey gave a higher polysaccharide
concentration and polysaccharide yield than acidic hydrolysed lactose. Maximum polysaccharide concentration (11.0 ± 0.5 g L−1), biomass dry weight (10.5 ± 0.4 g L−1), polysaccharide yield (47.2 ± 1.8%) and sugar utilization (93.2 ± 2.8%) were achieved using enzyme-hydrolysed whey (pH 6.5)
containing 25 g L−1 lactose and supplemented with K2HPO4 0.5%, L-glutamic acid 1%, olive oil 2.5%, and Tween 80 0.5%. In this case the pullulan content of the crude polysaccharide was 40%.
Received 16 December 1997/ Accepted in revised form 12 March 1999 相似文献
14.
Effects of sequential procedures required for cryopreservation of embryos excised from the recalcitrant seeds of Haemanthus montanus were assessed ultrastructurally and in conjunction with respiratory activity and the rate of protein synthesis. Fresh material
(water content, 5.05 ± 0.92 g g−1 dry mass) afforded ultrastructural evidence of considerable metabolic activity, borne out by respiratory rates. Neither exposure
to glycerol nor sucrose as penetrating and non-penetrating cryoprotectants, respectively, brought about degradative changes,
although increased vacuolation and autophagy accompanied both, while respiratory and protein synthetic activity were not adversely
affected. Glycerol-cryoprotected embryos flash dried to water contents >0.4 g g−1 showed organised ultrastructural features and considerable autophagy consistent with metabolic activity, and although respiratory
activity was lower, protein synthesis rate was enhanced relative to fresh material. However, at water contents <0.4 g g−1, embryo tissue presented a mosaic of cells of variable density and ultrastructural status, but trends in rates of respiration
and protein synthesis remained similar. Flash drying after sucrose exposure was accompanied by considerable ultrastructural
abnormality particularly at water contents <0.4 g g−1, lysis of individual and groups of cells and considerable depression of respiration, but not of protein synthesis. Success,
assessed as ≥50% axes forming seedlings after cryogen exposure, was obtained only when glycerol-cryoprotected embryos at water
contents >0.4 g g−1—in which the degree of vacuolation remained moderate—were rapidly cooled. The outcomes of this study are considered particularly
in terms of the stresses imposed by prolonged, relatively slow dehydration and ultimate water contents, on embryos showing
considerable metabolic activity. 相似文献
15.
The unloading of sucrose in the apical part of the hypocotyl of Ricinus communis L. seedlings was measured by 13C-nuclear magnetic resonance (NMR) spectroscopy. The cotyledons of the seedling were immersed in 5 mM Mes buffer containing
100 mM 13C-labeled sucrose. At intervals of 70–90 min, 13C-NMR spectra with broadband decoupling and nuclear Overhauser enhancement were acquired in vivo. The spectra showed growing 13C-resonances of the labeled positions in the sucrose molecule reaching steady-state labeling within 7–8 h. The specific 13C labeling of sucrose in the G1-position changed from 0.38 in the supplied sucrose solution to 0.16 in the sucrose extracted from the hypocotyl piece at
the end of the experiment (13 h). Labeling of starch (and other insolubles) in the hypocotyl piece was ca. 0.10. It is proposed
that the decreased specific labeling of unloaded sucrose is mostly due to the separate local pools of sucrose in the cortex
and pith parenchyma, respectively, and less to continuous starch degradation and conversion to sucrose. The report gives an
example of the application of 13C-NMR spectroscopy in assimilate allocation studies.
Received: 10 October 1998 / Accepted: 31 December 1998 相似文献
16.
J. P. Costanzo J. B. Moore R. E. Lee Jr. P. E. Kaufman J. A. Wyman 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1997,167(3):169-176
This investigation examined the influence of soil moisture and associated parameters on the cold hardiness of the Colorado
potato beetle (Leptinotarsa decemlineata Say), a temperate-zone species that overwinters in terrestrial burrows. The body mass and water content of adult beetles
kept in sand at 4 °C varied over a 16-week period of diapause according to the substratum's moisture content. Changes in body
water content, in turn, influenced the crystallization temperature (range −3.3 to −18.4 °C; n = 417), indicating that environmental moisture indirectly determined supercooling capacity, a measure of physiological cold
hardiness. Beetles held in dry sand readily tolerated a 24-h exposure to temperatures ranging from 0° to −5 °C, but those
chilled in sand containing as little as 1.7% water (dry mass) had elevated mortality. Thus, burrowing in dry soils not only
promotes supercooling via its effect on water balance, but may also inhibit inoculative freezing. Mortality of beetles exposed
to −5 °C for 24 h was lower in substrates composed of sand, clay and/or peat (36–52%) than in pure silica sand (78%) having
an identical water content (17.0% dry mass). In addition to moisture, the texture, structure, water potential, and other physico-chemical
attributes of soil may strongly influence the cold hardiness and overwintering survival of burrowing insects.
Accepted: 10 September 1996 相似文献
17.
Poly(hydroxybutyric acid) (PHB) was produced by a selectant of Azotobacter beijerinckii in media containing only organic nitrogen sources such as N substrates. The chosen compounds were casein peptone, yeast extract,
casamino acids and urea, each combined with carbon substrates glucose or sucrose. The PHB was synthesized under growth-associated
conditions. The concentrations amounted to more than 50% of cell dry mass on casein peptone/glucose as well as urea/glucose
medium within 45 h fermentation time. Corresponding to these yields, productivities of about 0.8 g PHB l−1 h−1 were discovered. The highest values increased to 1.06 g PHB l−1 h−1 on casein peptone/glucose medium and 1.1 g PHB l−1 h−1 on yeast extract/glucose medium after a period of 20 h. It was found that oxygen limitation was essential for successful
product formation, as demonstrated earlier. These data from basic research may support further investigations into the use
of technical proteins from renewable sources as substrates for PHB production by a strain of A. beijerinckii.
Received: 3 June 1997 / Received revision: 29 August 1997 / Accepted: 15 September 1997 相似文献
18.
E. J. Bormann M. Leißner M. Roth B. Beer K. Metzner 《Applied microbiology and biotechnology》1998,50(5):604-607
Polyhydroxybutyrate (PHB) was produced by Ralstonia eutropha DSM 11348 (formerly Alicaligenes eutrophus) in media containing 20–30 g l−1 casein peptone or casamino acids as sole sources of nitrogen. In fermentations using media based on casein peptone, permanent
growth up to a cell dry mass of 65 g l−1 was observed. PHB accumulated in cells up to 60%–80% of dry weight. The lowest yields were found in media without any trace
elements or with casamino acids added only. The residual cell dry masses were limited to 10–15 g l−1 and did not contain PHB. The highest productivity amounted to 1.2 g PHB l−1 h−1. The mean molecular mass of the biopolymer was determined as 750 kDa. The proportion of polyhydroxyvalerate was less than
0.2% in PHB. The bioprocess was scaled up to a 300-l plant. During a fermentation time of 39 h the cells accumulated PHB to
78% w/w. The productivity was 0.98 g PHB l−1 h1.
Received: 8 July 1998 / Accepted: 26 August 1998 相似文献
19.
Mannose is an unusable carbon source for many plants. In our study we compared the effects of mannose and sucrose on growth
and sucrose levels in azuki bean (Vigna angularis) cells grown in liquid media and in solid media. The suspension cells grew actively in a liquid medium containing 90 mM sucrose
but not in that containing 90 mM mannose, where the intracellular sucrose levels were reduced to 20% or less of those in sucrose-grown
cells. These results suggested that the limited conversion of mannose to sucrose resulted in cell growth inhibition. When
sucrose-grown suspension cells (1 × 105) were transferred onto agar medium containing mannose, they grew little initially, but, after a month lag period, they started
to form many callus colonies at a high apparent variation rate (1.3 × 10−3). Time-course studies for sugar and enzyme analysis revealed that the mannose-accommodated cells were capable of converting
mannose to sucrose, with enhanced phosphomannose isomerase activity. The mannose-accommodated cells actively grew in liquid
medium with sucrose but lost their ability to grow with mannose again, suggesting a specific trait of callus culture for mannose
utilization. The possible differences in the metabolic activities and other physiological characteristics are discussed between
callus and suspension cells.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
20.
Shoot tips from in vitro-grown, cold-hardened stock plants of white poplar (Populus alba L.) were successfully cryopreserved at –196 °C by one-step vitrification. After preculturing at 5 °C for 2 days on hormone-free
MS medium containing different sucrose concentrations, and loading for 20 min with 2 m glycerol and 0.4 m sucrose, shoot tips were treated with the PVS2 vitrification solution and plunged directly into liquid nitrogen. Best survival
rate (90%) was obtained when shoot tips were precultured on 0.09 m sucrose, hormone-free MS medium, vitrified by exposure to PVS2 solution for 60 min at 0 °C and, following cryopreservation,
rewarmed at 40 °C and washed in 1.2 m sucrose solution for 20 min. Regrowth was improved by plating shoot tips on a gelled MS medium containing 1.5 μm N6-benzyladenine plus 0.5 μm gibberellic acid, while shoot rooting was achieved on MS medium containing 3 μm indole-3-butyric acid. Following this procedure, almost 60% rooted shoots were obtained from cryopreserved shoot tips.
Received: 1 February 1999 / Revision received: 3 May 1999 · Accepted: 21 May 1999 相似文献