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81.
The presence of chlorophyll b and the estimation of phaeopigments in marine phytoplankton 总被引:1,自引:0,他引:1
A reverse-phase h.p.l.c. technique was used to estimate theconcentration of chlorophyll b in phytoplankton cultures, fecalpellets of Calanus pacificus, and suspended paniculate matterfrom the Central North Pacific, Oregon coastal waters, and DabobBay (a temperate fjord in Puget Sound, WA, USA). The purposewas to assess the distribution of this pigment in the euphoticzone and its effect on the fluorometnc estimation of phaeopigments.Analyses of natural waters confirm high chlorophyll b concentrations(median mass ratio of b:a > 0.3) at the depth of the chlorophylla maximum in tropical waters while values for temperate planktonare relatively low (median mass ratio of chl b:a = 0.05) andpatchy. Zooplankton fecal pellets showed a significant enrichmentin chlorophyll b, suggesting grazing as a mechanism to explainhigh concentrations of this pigment at the bottom of the euphoticzone. It is estimated that the presence of chlorophyll b couldcause an average overestimation of phaeopigment concentrationby the fluorometnc technique of 38% between 0 and 200 m in theCentral North Pacific. This effect is more pronounced at thelayer of chlorophyll b maximum (120140 m).
1Present address: Marine Biology Research Division, A-002, ScrippsInstitution of Oceanography, La Jolla, CA 92093, USA 相似文献
82.
Axillary shoot producing cultures were obtained from microcuttings and shoot tips of Calluna vulgaris cv. H.E. Beale. For cultures derived from microcuttings the highest multiplication rate of 38 shoots (5 mm or longer) was obtained on a reduced salt medium with the addition of 0.5 mgl-1 2-isopentenyladenine (2iP) during an 8 week subculture. For shoot tip derived cultures 0.2 mgl-1 6-benzyladenine (BA) was the best cytokinin and led to a multiplication rate of 26 for a 6 week subculture. The addition of 1 g/l casein hydrolysate to a multiplication medium enhanced shoot proliferation in presence of 0.5 mgl-1 BA.Despite various auxin treatments shoots formed no roots in vitro but rooted readily if transferred to a peat substrate ex vitro. A high rooting percentage (80%) was also obtained with shoots taken from the end of a multiplication phase and rooted directly. An additional subculture on low auxin containing media before transfer to peat substrate is recommended because the shoot condition can be improved in this way. A high number of rooted plantlets was produced, so the methods described will allow mass propagation. 相似文献
83.
The phosphate metabolism of Platymonas subcordiformis was investigated by 31P-NMR spectroscopy with special attention on the effect of external pH. Glycolyzing cells and cells energized by respiration or photosynthesis gave spectra dependent upon their metabolic state. The transition from deenergized to energized states is accompanied by a shift of cytoplasmic pH from 7.1–7.4, an increase of ATP level and-in well energized cells-the appearance of a new signal tentatively assigned to phosphoarginine.The spectra remain stable over a wide range of external pH. Cytoplasmic pH is well regulated in respiring cells for external pH in the range 5.3–12.3. The typical 0.4 units difference of internal pH in energized as compared to deenergized cells is not affected by external pH in the range 6–12. The intensity of a signal attributed to PEP is markedly increased at high external pH. pH regulation is less efficient below external pH of 6 in deenergized cells. Below pH 3.8 oxidative phosphorylation ceases. Upon raising cytoplasmic pH to 7.4 in deenergized cells polyphosphate chains start to disintegrate.Abbreviations PEP
Phosphoenolpyruyate
- P
i
inorganic phosphate
- PP
i
inorganic pyrophosphate
- poly P
polyphosphates
- PP-1, PP-2, PP-3
terminal, second, and third phosphate residue of polyphosphates
- PP-4
core phosphate residues of polyphosphates
- pH
i
, pH
o
internal (cytoplasmic) and external pH
- NTP/NDP
nucleotide triphosphate/-diphosphate
- S/N
signal to noise ratio 相似文献
84.
Harry J. Klee Maria B. Hayford Stephen G. Rogers 《Molecular & general genetics : MGG》1987,210(2):282-287
Summary Cloning of genes by transformation with genomic banks and rescue of a phenotype has been extensively used in bacterial systems. This approach has not been possible in plant systems because of the large genome sizes and poor transformation frequencies of most plant species. Recent advances in plant transformation permit the generation of large numbers of transformants in petunia. We have used this system to rescue a model gene encoding resistance to kanamycin by shotgun cloning. The gene encoding neomycin phosphotransferase (NPTII) was introduced into the genome of Arabidopsis thaliana by Agrobacterium tumefaciens-mediated transformation. A genomic bank of DNA from this tissue was constructed in a cosmid vector containing features which would allow its use in plant transformation. The unselected genomic bank was mobilized from Escherichia coli to A. tumefaciens and used to retransform petunia leaf discs. The rescued gene was identified by its ability to confer a kanamycin-resistant phenotype in petunia tissue. The presence of the NPTII gene was confirmed by nopaline assay and Southern blot analysis. This experiment demonstrates the feasibility of gene rescue, in certain circumstances, in plants. 相似文献
85.
The action of the herbicide glyphosate [N-(phosphonomethyl)-glycine] on phenolic metabolism and phenylalanine ammonia lyase (PAL; EC 4.3.1.5) activity was investigated in yellow nutsedge (Cyperus esculentus L.). Glyphosate caused significant increases in the amount of total soluble hydroxyphenolics in the three fractions studied (neutral, acid and residual). Qualitative and quantitative differences in relation to these fractions and the amount of applied glyphosate were observed. Most of the phenolic compounds which increased after glyphosate treatment were benzoic acids (gentisic. p -OH-benzoic, salicylic and vanillic). Gentisic acid showed the greatest increase in neutral and acid fractions, being twenty- and four-fold, respectively, of the amount found in the control. PAL activity was not affected by the lowest doses of glyphosate (10−4 and 10−3 M) , but a dramatic decrease in PAL activity was observed after 10−2 M treatment. These findings, together with the low levels of cinnamic acids measured in treated yellow nutsedge plants, suggest that PAL activity is only marginally involved in glyphosate action. Since the herbicidal action probably takes place at 5-enol-pyruvylshikimate-3-P synthase (EC 2.5.1.19), an alternative pathway to PAL in phenolic biosynthesis should be activated yielding benzoic acids. 相似文献
86.
The effects of Rhizobium strain and its interaction with plant cultivar were examined in glasshouse-grownPhaseolus vulgaris in two experiments where the physiological attributes defining the symbiotic efficiency were determined.
Strains of Rhizobium significantly affected nodulation, rates of N accumulation, partitioning of N within the mature shoot
and remobilizaton of the N stored in the vegetative organs to the seeds.
The most efficient symbiosis (strain CO5 with Negro Argel), in comparison with the least efficient symbiosis (strain 127 K-17
with Venezuela-350) showed higher rates of C2H2 reduction from flowering to mid pod fill stage, evolved less hydrogen from nodules and showed higher rates of N transport
as well as higher percentages of ureide-N in the xylem sap. At maturity, the best cultivar/strain association exceeded the
total N accumulated in the seed and the harvest index of the poorest symbiosis in 88% and 20%, respectively. The other symbiotic
combinations were intermediate in all characteristics.
Nitrogen accumulation in plant shoot showed highly significant correlation with acetylene reduction rates, nodule relative
efficiency, total N transport in the xylem sap and percentage of N transported as ureides. 相似文献
87.
Carlos Eduardo Falavigna da Rocha Maria Helena Gonzaga de Carvalho Bjornber 《Hydrobiologia》1987,153(2):97-107
Cyclopid copepods collected mainly in aquatic microcosms and semiterrestrial habitats in the Juréia Ecological Reserve are studied. Hesperocyclops herbsti and Bryocyclops campaneri are described as new species and their taxonomical relationships discussed. Females of Muscocyclops operculatus (Chappuis) are redescribed and the males described for the first time. An emended diagnosis for Muscocyclops is proposed. 相似文献
88.
Enzymatic conversion of glutamate to delta-aminolevulinic acid in soluble extracts of Euglena gracilis 总被引:7,自引:0,他引:7
Glutamate was converted to the chlorophyll and heme precursor delta-aminolevulinic acid in soluble extracts of Euglena gracilis. delta-Aminolevulinic acid-forming activity depended on the presence of native enzyme, glutamate, ATP, Mg2+, NADPH or NADH, and RNA. The requirement for reduced pyridine nucleotide was observed only if, prior to incubation, the enzyme extract was filtered through activated carbon to remove firmly bound reductant. Dithiothreitol was also required for activity after carbon treatment. delta-Aminolevulinic acid formation was stimulated by RNA from various plant tissues and algal cells, including greening barley leaves and members of the algal groups Chlorophyta (Chlorella vulgaris, Chlamydomonas reinhardtii), Rhodophyta (Cyanidium caldarium), Cyanophyta (Anacystis nidulans, Synechocystis sp. PCC 6803), and Prochlorophyta (Prochlorothrix hollandica), but not by RNA derived from Escherichia coli, yeast, wheat germ, bovine liver, and Methanobacterium thermoautotrophicum. E. coli glutamate-specific tRNA was inhibitory. Several of the RNAs that did not stimulate delta-aminolevulinic acid formation nevertheless became acylated when incubated with glutamate in the presence of Euglena enzyme extract. RNA extracted from nongreen dark-grown wild-type Euglena cells was about half as stimulatory as that from chlorophyllous light-grown cells, and RNA from aplastidic mutant cells stimulated only slightly. delta-Aminolevulinic acid-forming enzyme activity was present in extracts of light-grown wild-type cells, but undetectable in extracts of aplastidic mutant and dark-grown wild-type cells. Gabaculine inhibited delta-aminolevulinic acid formation at submicromolar concentration. Heme inhibited 50% at 25 microM, but protoporphyrin IX, Mg-protoporphyrin IX, and protochlorophyllide inhibited only slightly at this concentration. 相似文献
89.
Pertussis Toxin Attenuates D2 Inhibition and Enhances D1 Stimulation of Adenylate Cyclase by Dopamine in Rat Striatum 总被引:2,自引:1,他引:1
The response of adenylate cyclase to GTP and to dopamine (DA) was investigated in synaptic plasma membranes isolated from rat striatum injected with pertussis toxin, which inactivates the inhibitory guanine nucleotide-binding regulatory protein (Ni) of adenylate cyclase. Pertussis toxin treatment reverted the inhibitory effects on the enzyme activity elicited by micromolar concentrations of GTP and reduced by 50% the DA inhibition of cyclase activity via D2 receptors. The toxin treatment enhanced the net stimulation of enzyme activity by DA in the presence of micromolar concentrations of GTP. However, the stimulatory effect of the selective D1 receptor agonist SKF 38393 was not significantly affected. The data indicate that Ni mediates D2 inhibition of striatal adenylate cyclase and participates in the modulation of D1 stimulation of the enzyme activity by DA. 相似文献
90.