共查询到20条相似文献,搜索用时 331 毫秒
1.
Bernd Egger Werner Einig Armin Sclereth Thomas Wallenda Elisabeth Magel Anja Loewe Rüdiger Hampp 《Physiologia plantarum》1996,96(1):91-100
Starch and sucrose metabolism of one- and two-year-old needles of Norway spruce (Picea abies [L.] Karst., about 30 years old) was investigated from three months before until three months after bud break at a natural site. We distinguish different metabolic states according to the extractable activities of enzymes (α-amylase [EC 3.2.1.1], ADP-glucose pyrophosphorylase [AGP, EC 2.7.7.27], D-enzyme [EC 2.4.1.25], starch phosphorylase [STP. EC 2.4.1.1]), sucrose phosphate synthase [SPS, EC 2.4.1.14], sucrose syntbase [SS, EC 2.4.1.13]. acid invertase [AI, EC 3.2.1.261) and pool sizes of related metabolites (starch, glucose, fructose, sucrose, raffinose, stachyose, fructose 6-phosphate [F6P], glucose 6-phosphate [G6P], fructose 2,6-bisphosphate [F26BP], and inorganic phosphate [P1]). The period ending with bud break was characterized by high rates of net photosynthesis, a pronounced decrease in the amount of soluble sugars, and a steep rise in starch (from the detection limit to approximately 600 nmol glycosyl units [mg dry weight]-1). In parallel, the extractable activity of AGP increased, while D-enzyme was on a relative high level when compared with the period after bud break. With respect to sucrose metabolism, F26BP, an inhibitor of sucrose synthesis, decreased from 1 to 0.4 pmol (mg dry weight)-1. This was complemented by SPS activity, which was due to both increased protein levels shown by immunoblotting and activation under metabolite control (high levels of G6P and a low Pi/G6P ratio). This indicates a high capacity of synthesis of starch and sucrose in the period before bud break. These observations are in accordance with estimates of photosynthetic carbon gain, which indicate that in early spring large amounts of carbon from current photosynthesis are exported out of the needles. In addition, the content of nonstructural carbohydrates (expressed as hexoses) increased in the bark of the stem. This could also be a consequence of an enhanced carbon export from the needles. After the onset of bud break, starch concentration decreased in all tissues under investigation. In contrast, the level of total nonstructural carbohydrates in the outermost sapwood nearly doubled from bud break until the end of sampling. In the needles, net photosynthesis was reduced by about 75% and a decrease in SPS activity and protein level were found together with lower G6P concentration, and an increased Pi/G6P ratio. These results suggest that during that period sucrose synthesis was reduced in the older needles. In addition, under conditions of reduced photosynthesis, carbon demand of current year needles was in part ensured by the mobilization of starch in the older needles. Taken together our data show that before bud break carbon metabolism of mature leaves is related with the sink demands of storage organs. After bud break the accumulated assimilate pools in needles and stem, mainly the bark, are mobilized and support carbon supply to new tissues. 相似文献
2.
Alan B. Darlington Anna Halinska James F. Dat T. J. Blake 《Trees - Structure and Function》1997,11(4):223-228
Plant responses to saturation vapour pressure deficit (SVPD) were studied by subjecting black spruce [Picea mariana (Mill) B.S.P.] and jack pine seedlings (Pinus banksiana Lamb.) to humid (0.3 – 0.8 kPa) or dry (2.0 – 2.5 kPa SVPD) regimes for 4 weeks using a computer-controlled environmental
system to control diurnal variation in SVPD. Dry matter accumulation in needles was not altered by increasing SVPD. However,
root growth declined by 60% which increased shoot to root ratio and reduced total seedling dry weight in both black spruce
and jack pine. Relative growth rate of jack pine also declined to about half the rate of plants grown under humid conditions.
In situ root marking studies showed that the decline in root growth of jack pine under the high SVPD was the result of reduced
lateral root initiation, whereas root elongation was unaffected by humidity. A 4-week exposure to dry air increased abscisic
acid (ABA) levels in needles, but not roots, of jack pine whereas ABA levels in black spruce were not altered. A short (3-day)
exposure failed to increase needle ABA levels in either species. These results suggest that the responses of conifers to dry
air were not the result of ABA accumulation.
Received: 24 March 1996 / Accepted: 30 May 1996 相似文献
3.
The photosynthetic capacity of frost-hardy and frost-sensitive needles of 3-year-old Scots pines and the allocation and utilization
of assimilated carbon was examined during winter and early spring. The photosynthates of the whole trees were labelled by
14CO2 fixation and after chase periods of from 7 days to 4 months under natural climatic conditions, the distribution of radiocarbon
in the various tissues of the trees was determined. During winter maximal photosynthetic rates of 1-year-old needles were
considerably lower than in summer when calculated on a leaf area basis. However, when related to the chlorophyll content these
discrepancies disappeared. The decrease of the photosynthetic capacity upon frost-hardening could be attributed to a two-
to three-fold reduction in the chlorophyll content of the needles. The pulse-chase experiments showed that photosynthesis
during the cold season preferentially provides substrates for respiration. Half of the assimilated 14C was respired during the first week, and after chase periods of 3 – 4 months the trees contained not more than 10 – 20% of
the radiocarbon. The carbon, which was exported by the needles, was translocated basipetally via the twigs and the stem to
the roots. Whereas in the axial system incorporation of radiocarbon into storage compounds, like starch, and into cell wall
material was almost negligible during the cold season, in the roots one-third of the radiocarbon was recovered from starch
2 months after the 14C-pulse. In contrast to the above-ground parts of the trees, where starch content was very low during winter, in the roots
considerable amounts of starch, up to 450 μmol hexose units · g– 1 DW, were found even during mid-winter. In early spring the radiocarbon in the cell wall-, lipid-, and starch-fraction accounted
for more than 80% of the 14C recovered at that time from the axial system. Incorporation of minor quantities into the cell wall fraction of the roots
during winter and early spring indicate continuous root growth during the cold period as well as in early spring. Whereas
during winter the buds did not attract freshly assimilated carbon, in spring just before bud break substantial amounts of
carbon were translocated from the needles into the buds. In contrast, remobilization of carbon, which had been assimilated
during autumn of the previous year, and import into the sprouting buds could not be demonstrated.
Received: 3 November 1995 / Accepted: 1 March 1996 相似文献
4.
J.-P. Schnitzler Tim P. Jungblut Carmen Feicht Matthias Köfferlein Christian Langebartels W. Heller Heinrich Sandermann Jr. 《Trees - Structure and Function》1997,11(3):162-168
Cultivation of Scots pine (Pinus sylvestris L.) seedlings under simulated global radiation including the UV-B band (280 – 320 nm; 220 mW m–2 UV-BBE) led to increased formation of the diacylated flavonol glucosides 3″,6″-di-p-coumaroyl-astragalin and 3″,6″-di-p-coumaroyl-isoquercitrin in primary and cotyledonary needles, respectively. 3″,6″-Di-p-coumaroyl-astragalin was also the main constitutive diacylated flavonol glucoside in both needle types. This compound predominantly
accumulated in primary needles upon UV-B irradiation, and reached concentrations of 2.4 μmol g–1 fresh weight (fw). Its concentration was only weakly affected in cotyledonary needles. 3″,6″-Di-p-coumaroyl-isoquercitrin was mainly induced in cotyledonary needles with maximum concentrations of 0.8 to 0.9 μmol g–1 fw, but was virtually unaffected in primary needles under the same irradiation conditions. Pulse labelling with L-(U-14C)phenylalanine revealed that these metabolites were formed de novo. Phenylalanine ammonia-lyase (EC 4.3.1.5) and chalcone
synthase (EC 2.3.1.74) were only slightly induced by the UV-B treatment. The results described here represent the first report
on UV-B-induced flavonoid biosynthesis in a conifer species.
Received: 5 December 1995 / Accepted: 20 March 1996 相似文献
5.
Transgenic potato (Solanum tuberosum L.) plants were created with sense and antisense copies of the potato D-enzyme (disproportionating enzyme; EC␣2.4.1.25) cDNA
linked to patatin and cauliflower mosaic virus 35 S promoters, and screened for D-enzyme activity in tubers. Transformants
with sense constructs mostly had wild type D-enzyme activity but two plants had only about 1% wild-type activity. Transformants
with antisense constructs had activity ranging from 90% to about 1% of wild type. Three 35 S antisense plants with very low
activity were analysed in detail. Western blot analysis showed that D-enzyme was present in greatly reduced amounts in tubers
and in leaves, whereas plastidic starch phosphorylase (EC 2.4.1.1) was unaffected. The lack of D-enzyme resulted in slow plant
growth but development was otherwise apparently normal. Furthermore, the starch content of tubers was not appreciably altered
in amount, proportion of amylose, molecular weight of debranched amylopectin, or branch chain length, despite the lack of
D-enzyme. These results do not indicate a direct requirement for D-enzyme in the synthesis and accumulation of storage starch
in tubers. The results are discussed in terms of the known reactions catalysed by D-enzyme and possible involvement of D-enzyme
in starch metabolism.
Received: 12 November 1997 / Accepted: 23 December 1997 相似文献
6.
Marion-Gabriele Ott Daniela N. Männel Harald Gallati Matthias Goerig Ulrich Raeth 《Cancer immunology, immunotherapy : CII》1996,42(1):31-37
Tumor necrosis factor α (TNFα) and interferon γ (IFNγ) are important immunomodulators. They are capable of acting in a synergistic
manner on tumor cells in vitro and in vivo. In a clinical phase I study 13 patients with malignant ascites due to abdominal
spread of different primary tumors received intraperitoneally (i. p.) TNFα and IFNγ once weekly over 3 – 8 weeks in order
to evaluate the effect of locoregionally administered TNFα/IFNγ on ascites formation. Therefore some peripheral and local
immunological functional parameters of peripheral blood and malignant ascites were investigated. Mononuclear lymphocytes and
natural killer (NK) cell activity of peripheral blood and ascites, TNF-inhibitory activity, soluble p55 and p75 TNF receptors,
and prostaglandin E2 values in ascites were measured immediately before and 24 h after each TNFα/IFNγ infusion. Peripheral mononuclear lymphocytes
and NK activity decreased significantly 24 h after i. p. TNFα/IFNγ application. However, over the entire treatment schedule,
peripheral NK activity in all responders showed a continuous increase, when compared to pre TNFα/IFNγ treatment levels. In
contrast, NK activity in non-responders constantly decreased. In contrast to non-responders, TNF-inhibitory activity and soluble
p55 TNF receptor levels, determined in ascites, decreased in responders. Taken together, our findings suggest, that successful
locoregional i. p. TNFα/IFNγ therapy induces systemic immunological reactions possibly after saturation of soluble p55 TNF
receptors in ascites, which leads to an increase of peripheral NK activity.
Received: 28 September 1995 / Accepted: 16 November 1995 相似文献
7.
The development of α-amylase (EC 3.2.1.1) activity in wheat was followed during 4 days of germination. The enzyme was purified
and separated by gel chromotography into two distinct entities (α-amylase I and α-amylase II), with different molecular weights
and isoelectric points. α-Amylase I contained a much higher content of sugars than α-amylase II, which decreased as the germination
proceeded. The time sequence analysis of the starch degradation pattern showed that on the 4th day of germination, 15% of
the total activity was present in α-amylase I and the rest in a-amylase II. Similarly, differences in the relative rates of
synthesis of their isoenzymes were observed. α-Amylase I was resolved on the 4th day of germination, only into 3 isoenzymes,
whereas α-amylase II could separate into 4 isoenzymes. The enzyme activity was however maximal in the most electropositive
isoenzyme in both the components. 相似文献
8.
Carbon allocation in developing spruce needles. Enzymes and intermediates of sucrose metabolism 总被引:2,自引:0,他引:2
Rüdiger Hampp Bernd Egger Susanne Effenberger Werner Einig 《Physiologia plantarum》1994,90(2):299-306
In lyophilized needles of Norway spruce ( Picea abies [L.] Karsten) and starting from bud break, we determined enzyme activities (sucrose phosphate synthase [SPS; EC 2.4,1.14]. sucrose synthase [SS; EC 2.4,1.13]. acid invertase [AI; EC 3.2,1.26]) and intermediates (starch, sucrose, glucose, fructose; fructose 6-phosphate, fructose 2.6-bisphosphate [F26BP]) of carbohydrate metabolism together with needle weight, shoot length, chlorophyll and protein. For up to 110 days after bud break, samples were taken twice a week from about 25-year-old trees under field conditions. At least three periods can be distinguished during needle maturation. During the first period (up to 45 days after bud break) Al showed the highest extractable activity. This coincided with very high levels of F26BP (up to 11 pmol [mg dry weight]−1 ) and a transient increase of starch in parallel to a decrease of sucrose. The interval between 45 and 70 days after bud break was characterized by high SS activity (ratio of fructose/glucose >1), much decreased levels of F26BP (down to below 1 pmol [mg dry weight]−1 ), and a pronounced increase in the dry weight/fresh weight ratio. In parallel, starch declined and soluble carbohydrates increased. Finally, needle maturation was characterized by decreasing SS and continuously increasing SPS activities, so that the ratio of SPS/SS increased more than 6-fold. AI. however, did not decline with maturation. Changes in pool sizes of metabolites and enzyme activities (AI. SPS) are consistent with current concepts on sink/source transition. SS is obviously important with regard to the synthesis of structural polysaccharides. 相似文献
9.
During seedling growth of mungbean in dark, depletion of cotyledonary starch is reflected by an increase in starch content
of root and shoot. With progress of seedling growth, amylolytic activity increases in all organs i.e. cotyledons, shoots and roots. A rapid turnover of starch in shoots and roots has been proposed. Amylase activity of seedlings
was in the order of cotyledons>shoots>roots. Five days after germination (DAG) α-amylase from cotyledons of mungbean seedlings
was purified using ammonium sulphate precipitation, DEAE cellulose and sephadex G-150 column chromatography. Phytic acid was
a stronger inhibitor of α-amylase than EDTA. Phytic acid, Hg2+, Zn2+ and Mn2+ were non-competitive inhibitors and the corresponding Ki values were 5.0–5.7, 0.36–0.38, 2.6–3.8 and 0.7–0.8 mol·M−3. Elution patterns of α-amylases of cotyledons, shoots and roots on sephadex G-100 column showed that cotyledonary α-amylase
had a higher molecular mass than that of shoot and root α-amylases which had identical molecular masses. All α-amylases showed
the same optimum pH 5.0 whereas optimum temperature was 55 °C for cotyledonary and 45 °C for shoot and root α-amylases. In
all these tissues α-amylases were stable to 30 min heat treatment at 50 °C however unlike cereal α-amylases they lost activity
at 70 °C. Km for α-amylases from cotyledons, shoots and roots with starch was 1.9, 4.3 and 6.6 mg per cm3, respectively. α-amylase of cotyledons and roots showed activity in reactions with various substrates in the order of starch>amylose>dextrin-I=dextrin-IV>α-cyclodextrin=β-cyclodextrin>amylopectin>pullulan.
The shoot α-amylase showed high activity with amylopectin, which was comparable with that obtained with amylose, and the activity
with α and β-cyclodextrin was higher in comparison with dextrin-I and IV. The α-amylases from these tissues liberated maltose,
maltotriose and higher oligosaccharides from starch. It could be concluded that amylases from different organs of a seedling
could have different physical and kinetic properties. 相似文献
10.
Kiyoshi Asai Haruki Kato Shigeru Kimura Shigehiko Mukai Yutaka Kawahito Hajime Sano Motoharu Kondo Keiko Akaogi K. Hirose 《Cancer immunology, immunotherapy : CII》1996,42(5):275-279
We have elucidated the direct effects of PSK (a protein-bound polysaccharide) and OK-432 (a streptococcal preparation), both
immunomodulating drugs, on the gene expression for an inducible nitric oxide synthase and on the production of nitric oxide
(NO) in the RAW264.7 murine macrophage cell line. As determined by northern blot analysis, both immunomodulating drugs were
potent inducers of gene expression for inducible NO synthase when cells were costimulated with interferon-γ (IFNγ). Expression
of mRNA for the enzyme occurred in a dose-dependent manner after 3 h, when 10 – 50 μg/ml PSK or 0.001 – 1 KE/ml OK-432 was
used. Furthermore, NO was also produced in response to these drugs, as detected by the Griess reagent reaction. The enhancement
of NO synthesis was thought to be mediated, in part, through tumor necrosis factor α (TNFα) induction by these agents, since
a neutralizing antibody to TNFα significantly suppressed NO production in RAW264.7 cells stimulated with PSK or OK432 in combination
with IFNγ. We speculate that NO production may play a role in tumoricidal and microbicidal activities of PSK or OK-432 in
vivo.
Received: 9 August 1995 / Accepted: 1 April 1996 相似文献
11.
Effects of SO2, aqueous fluoride (NaF) and a solution of nitrogen compounds (NH4NO3) on the visible symptoms, pollutant accumulation and ultrastructure of Scots pine (Pinus sylvestris L.) and Norway spruce [Picea abies (L.) Karst.] seedlings were studied in an open-air experiment lasting for 3 consecutive years. Visible injury symptoms were
most pronounced in combination exposures and whenever F was applied. Visible symptoms correlated well with needle pollutant
concentrations. Exposure to NaF increased needle F contents particularly when F was applied with SO2 or NH4NO3. This suggests that a reduction in N or SO2 emissions, in F polluted areas, could improve the condition of conifers via decreased accumulation of phytotoxic F in the
needles. Norway spruce needles accumulated 2 – 10 times as much S and F as those of Scots pine. Microscopic observations showed
various changes in the needle mesophyll cell ultrastructure. In both species, exposure to SO2 increased significantly the amount of cytoplasmic vacuoles, suggesting detoxification of excess sulphate or low pH. F treatments
resulted in a significant enlargement of plastoglobuli in Scots pine and a darkening of plastoglobuli in Norway spruce. All
exposures enhanced the accumulation of lipid bodies. An increased portion of translucent plastoglobuli was most pronounced
in N treatments. Many of the ultrastructural changes and visible symptoms appeared only as number of years exposed increased,
indicating that long-term experiments are needed. Both visible symptoms and ultrastructural changes pointed to the more pronounced
sensitivity of Norway spruce compared to Scots pine. Ultrastructural results mostly supported earlier qualitative observations
of F, N and SO2 effects on needle mesophyll cell ultrastructure. However, no reduction of thylakoids in SO2 containing exposure or curling of thylakoids in F exposure could be detected in the present study.
Received: 5 December 1994 / Accepted: 28 April 1995 相似文献
12.
A truncated mutant α-amylase, Xa-S2, was obtained from Xanthomonas campestris wild type α-amylases (Xa-WT) through random mutagenesis that contained 167 amino acid residues (approx 65% shorter than that
of Xa-WT). Secondary structure prediction implied that Xa-S2, would be unable to form the whole (β/α)8-barrel catalytic domain and did not have the three conserved catalytic residues of wild type α-amylase, but it still displays
the starch-hydrolyzing activity. Xa-S2 was prepared, characterized and compared to the recombinant wild-type enzymes. The
K
m for starch was 32 mg/ml; activity was optimal at pH 6.2 and 30°C. In contrast, the K
m for starch of Xa-WT was 8 mg/ml and optimal enzyme activity was at pH 6.0–6.2 and 45–50°C. Our results suggested that Xa-S2
is a new amylase with a minimal catalytic domain for hydrolyzing substrates with of α-1,4-glucosidic bonds.
T. Ke and X. D. Ma contributed equally to this work 相似文献
13.
14.
15.
Vered Naor Jaime Kigel Yosi Ben-Tal Meira Ziv 《Journal of Plant Growth Regulation》2008,27(3):211-220
Phenologic changes and variation in the level of endogenous gibberellins (GAs), abscisic acid (ABA), carbohydrate content,
and α-amylase activity were examined in colored Zantedeschia spp. cv. Cala Gold. These changes were examined in the primary bud tissues and in the attached tuber tissue during the growth
cycle. Dormant tubers were dry-stored at 20°C for 3 months, planted in a phytotron, and grown under 22/16 ± 1°C. Plant development
was monitored under continued irrigation until leaf senescence and tuber dormancy. GAs and ABA were extracted from the primary
bud tissues, fractionated by HPLC, and analyzed using GC-SIM. Starch, glucose, soluble protein, and α-amylase activity were
monitored in the tuber tissue attached to the primary bud. Endogenous changes in GAs and ABA in the primary bud were correlated
with endogenous changes in carbohydrate content and α-amylase activity in the attached tuber tissue. These correlations were
observed during the rest and the growth periods and were associated with developmental changes in the plant, that is, bud
dormancy relaxation, bud growth, and inflorescence differentiation. ABA content decreased and a transient pulse of GA was
measured in the primary bud concomitantly with the onset of shoot elongation in dry tubers during storage, before planting.
The sharp increase of GAs in the bud preceded inflorescence differentiation as observed in dissected apices by about 15 days,
as well as the increase in α-amylase activity in the attached tuber tissue. A steep decrease in starch level was measured
in the tuber after planting, concomitantly with massive plant growth. These findings suggest a possible involvement of gibberellin
in the initiation of α-amylase activity during dormancy relaxation in colored Zantedeschia and in the autonomous induction of flowering. 相似文献
16.
The physiological properties of transgenic tobacco plants (Nicotiana tabacum L.) with decreased or increased transport capacities of the chloroplast triose phosphate/phosphate translocator (TPT) were
compared in order to investigate the extent to which the TPT controls metabolic fluxes in wild-type tobacco. For this purpose,
tobacco lines with an antisense repression of the endogenous TPT (αTPT) and tobacco lines overexpressing the TPT gene isolated
from the C4 plant Flaveria trinervia (FtTPT) were used. The F. trinervia TPT expressed in yeast cells exhibited transport characteristics identical to the TPT from C3 plants. Neither antisense TPT plants nor FtTPT overexpressors showed a phenotype when grown in a greenhouse in air. Contents
of starch and soluble sugars in upper source leaves were similar in TPT underexpressors and FtTPT overexpressors compared
to the wild type at the end of the photoperiod. The FtTPT overexpressors incorporated more 14CO2 in sucrose than the wild type, indicating that the TPT limits sucrose biosynthesis in the wild type. There were only small
effects on labelling of amino acids and organic acids. The mobilisation of starch was enhanced in αTPT lines but decreased
in FtTPT overexpressors compared to the wild type. Enzymes involved in starch mobilisation or utilisation, such as α-amylase
or hexokinase were increased in αTPT plants and, in the case of amylases, decreased in FtTPT overexpressors. Moreover, α-amylase
activity exhibited a pronounced diurnal variation in αTPT lines with a maximum activity after 8 h in the light. These changes
in starch hydrolytic activities were confirmed by activity staining of native gels. Activities of glucan phosphorylases were
unaffected by either a decrease or an increase in TPT activity. There were also effects of TPT activities on steady-state
levels of phosphorylated intermediates as well as total amino acids and malate. In air, there was no or little effect of altered
TPT transport activity on either rates of photosynthetic electron transport and/or CO2 assimilation. However, in elevated CO2 (1500 μl · l−1) and low O2 (2%) the rate of CO2 assimilation was decreased in the αTPT lines and was slightly higher in FtTPT lines. This shows that the TPT limits maximum
rates of photosynthesis in the wild type.
Received: 26 March 1999 / Accepted: 21 August 1999 相似文献
17.
Arsenic (As) is a potential contaminant of groundwater as well as soil in many parts of the world. The effects of increasing
concentration of As (25 μm and 50 μm As2O3) in the medium on the content of starch and sugars and activity levels of enzymes involved in starch and sugar metabolism
i.e. α-amylase, β-amylase, starch phosphorylase and acid invertase were studied in germinating seeds of two rice cvs. Malviya-36 and Pant-12 during 0–120 h period. As toxicity in situ led to a marked decline in the activities of α-amylase, β-amylase in endosperms as well as embryoaxes of germinating rice
seeds. The activity of acid invertase increased in endosperms as well as embryoaxes whereas starch phosphorylase activity
declined in endosperms but increased in embryoaxes under As treatment. In endosperms a decline in starch mobilization was
observed under As toxicity, however under similar conditions the content of total soluble sugars increased in embryoaxes.
The observed inhibition in activities of amylolytic enzymes might contribute to delayed mobilization of endospermic starch
which could affect germination of seeds in As polluted environment, while the induced acid invertase activity and increased
sugar accumulation in embryoaxes could serve as a possible component for adaptation mechanism of rice seedlings grown under
As containing medium. 相似文献
18.
α-Amylase (EC 3.2.1.1) expression was found in calli of French bean (Phaseolus vulgaris L. cv Goldstar). We examined enzyme activity in the calli to investigate influence of gibberellin and sugars on enzyme expression.
After subculture of the calli, α-amylase activity decreased, and then increased at a stationary phase of callus growth. Exogenous
application of gibberellin and an inhibitor of gibberellin synthesis, uniconazole, did not have any significant effects on
the enzyme expression. Sugar starvation increased the activity, while addition of metabolizable sugars, such as sucrose, glucose
and maltose, to the medium repressed expression. Addition of 6% mannitol, a non-metabolizable sugar, to the medium induced
higher α-amylase expression as compared to addition of 3% mannitol. This result suggests that osmotic stress enhances α-amylase
activity in the calli. Furthermore, high concentrations of agar in the medium increased α-amylase activity in the calli. It
is probable that high concentrations of agar prevented incorporation of nutrient into the calli and induced the α-amylase
activity in the calli. 相似文献
19.
Krzysztof J. Rakowski 《Trees - Structure and Function》1997,11(4):248-253
Eastern white pine (Pinus strobus L.) seedlings were pretreated with 12 h photoperiod to induce dormancy. Dormant plants were fumigated with 0.5 ppb (0.4 μg
m–3) or 2.0 ppb (1.6 μg m–3) hydrogen fluoride (HF) for 2 – 28 days. Plasma membranes were isolated from needles of treated and control seedlings to
determine their chemical composition and ATPase activity. For all analyses, only those plants which did not show needle necrosis
were selected. The amount of plasma membrane phospholipid expressed on a plasma membrane protein basis was higher after 2
days in the 0.5 ppb HF treatment as compared to controls. After 2 days of 2.0 ppb HF treatment as well as after 8 and 28 days
of both HF treatments phospholipid to protein ratios in fluoride treated seedlings were lower as compared to control levels.
A decrease in sterol levels could be observed after 2 days in both HF treatments. A large increase in the ratio of sterols
to proteins was observed in plasma membranes of eastern white pine seedlings treated with 0.5 ppb HF for 28 days. Increased
sterol to phospholipid ratios were observed after 8 and 28 days in 0.5 ppb and after 2 and 8 days of 2.0 ppb HF treatment.
A decrease in ATPase activity was observed after 8 days with both fluoride treatments. Drastic increase of ATPase activity
was observed after 28 days of HF treated plants. Observed changes of sterol and phospholipid levels after only 2 days of fumigation
suggest early fluoride effects on plasma membrane composition during plant dormancy.
Received: 25 October 1995 / Accepted: 24 May 1996 相似文献
20.
The plant cytoskeleton has been implicated in a variety of morphogenetic events in higher plants. Most of this work, however,
has concentrated on epidermal cells or primary tissues. We have investigated the cortical microtubular (CMT) and microfilament
(MF) components of the cytoskeleton in a secondary tissue – active vascular cambium of Aesculus hippocastanum L. (horse-chestnut) – and followed the changes in these components during the early stages of differentiation of fusiform
cambial derivatives to axial elements of the secondary vascular system. A correlative approach was used employing indirect
immunofluorescence microscopy of α-tubulin on 6 μm sections, and transmission electron microscopy of 60 nm sections. The study
has demonstrated a rearrangement of the CMT cytoskeleton, from random to helical, as fusiform vascular cambial cells begin
to differentiate as secondary phloem vascular tissue. A similar CMT rearrangement is seen as fusiform cambial cells begin
to differentiate as secondary xylem fibres. This rearrangement is interpreted as evidence of determination of cambial derivatives
towards vascular development. Axially-oriented MF bundles are present in fusiform cambial cells and their axial orientation
is retained in the vascular derivatives at early stages of their development even though the CMTs have become rearranged.
Received: 5 August 1996 / Accepted: 23 September 1996 相似文献