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71.
Effects of Growth Regulators on Polyamine Content and Peroxidase Activity in Hevea brasiliensis Callus 总被引:2,自引:0,他引:2
3, 4-dichlorophenoxyacetic acid (3,4-D) and benzylaminopurine(BAP) at 9 µM (control medium) was compared with 4.5,2.25, and 0.45 µM for ability to induce callogenesis andembryogenesis from seed explants of Hevea brasiliensis. Supplyingthese growth regulators at 4.5 µM for 20 d improved embryogenicpotential compared with the control medium (El Hadrami, Carronand d'Auzac, 1991, Annals of Botany 67, 511515), sustainedputrescine, spermidine and spermine at a higher level throughoutof much of the culture period (4070 d), and maintainedlow levels of peroxidase activity. In the control medium, poorcallus embryogenesis is considered a consequence of rapid ageingof tissues characterized by (i) acceleration of an early buttransient production of polyamines, which promoted embryogeniccapacity, and (ii) an early peak in peroxidase activity thatwas positively correlated with callus browning, one of the factorslimiting embryogenesis. Somatic embryogenesis, polyamines, peroxidase, Hevea brasiliensis, rubber-tree 相似文献
72.
The increase of glucose-6-phosphate dehydrogenase (G-6-PD) activityhas been proposed as an early marker of floral evocation inthe shoot apical meristem of spinach. This induction is obtainedby the transfer of vegetative plants from short days to continuouslight. The exposure of a single leaf to continuous light inducedthe same effect as that produced with the whole plant. In vegetativeconditions (short days), an electrical potential of ten volts(electrical current: 12·5 µA) applied to the petioleof a single leaf induced a weak increase of G-6-PD activityin the shoot apex, while under inductive conditions, this increasewas similar to that of control plants (transferred to continuouslight). Application of an electrical potential to the petioleand the root inhibits the increase linked to the inductive transfer.These results show that an externally applied electrical potentialmay interact with the natural electrical gradients along theshoot and consequently inhibit the normal floral developmentby an as yet unspecified mechanism. Spinacia oleracea, floral induction, interorganic relations, glucose-6-phosphate dehydrogenase, shoot apex, electrical potentials 相似文献
73.
Chloroplast DNA phylogeography of the argan tree of Morocco 总被引:7,自引:0,他引:7
Polymorphisms in the chloroplast genome of the argan tree (Sapotaceae), an endemic species of south-western Morocco, have been detected by restriction site studies of PCR-amplified fragments. A total of 12 chloroplast DNA (cpDNA) and two mitochondrial DNA (mtDNA) fragments were amplified and digested with a single restriction enzyme ( Hin fI). Polymorphisms were identified in six of the cpDNA fragments, whereas no mtDNA polymorphisms were detected in a survey of 95 individuals from 19 populations encompassing most of the natural range of the species. The cpDNA polymorphisms allowed the identification of 11 haplotypes. Two lineages, one in the south-east and the other in the north-west, divide the range of the argan tree into two distinct areas. The level of genetic differentiation measured at the haplotype level ( G STc = 0.60) (i.e. with unordered haplotypes) was smaller than when phylogenetic relationships were taken into account ( N STc = 0.71–0.74) (ordered haplotypes), indicating that population history must be considered in the study of the geographical distribution of cpDNA lineages in this species. If contrasted with the level of nuclear genetic differentiation measured in a previous study with isozymes ( G STn = 0.25), the results indicate a relatively high level of gene flow by seeds, or conversely a relatively low level of gene flow by pollen, as compared with other tree species. Goats and camels could have played an important role in disseminating the fruits of this tree. 相似文献
74.
In vivo administration of interleukin-2 protects susceptible mice from Theiler's virus persistence. 总被引:2,自引:1,他引:1 下载免费PDF全文
In vivo administration of interleukin-2 (IL-2)-secreting tumor cells results in complete protection against persistent infection by Theiler's murine encephalomyelitis virus (TMEV) in susceptible DBA/2 mice. The IL-2-mediated protection was found to depend on the inoculum size as well as the timing of IL-2 administration. IL-2-treated and TMEV-infected mice displayed a three- to fourfold relative increase in virus-specific cytotoxic T-lymphocyte (CTL) precursors. Thus, we postulate that the persistence of TMEV infection in susceptible mice reflects limited numbers of relevant CTL precursors and their time course of induction and activation. 相似文献
75.
An early, abundant cytotoxic T-lymphocyte response against Theiler's virus is critical for preventing viral persistence. 总被引:2,自引:1,他引:1 下载免费PDF全文
In genetically susceptible strains of mice, the DA strain of Theiler's virus, a picornavirus, causes a persistent infection of the white matter of the spinal cord associated with chronic demyelination. In resistant strains, on the other hand, the infection is cleared within 1 to 2 weeks. In this article, we show that Theiler's virus induces a rapid and abundant cytotoxic T lymphocyte (CTL) response in resistant C57BL/6 mice, while the response remains low throughout infection in susceptible SJL/J mice. This difference can be referred to a higher number of virus-specific CTL precursors in C57BL/6 mice. These observations indicate that the efficient induction of virus-specific CTL precursors is critical for avoiding the establishment of a persistent picornaviral infection. 相似文献
76.
BETHAN V. PURSE BENJAMIN J. J. MCCORMICK PHILIP S. MELLOR MATTHEW BAYLIS JOHN P. T. BOORMAN DAVID BORRAS IBRAHIM BURGU RUBEN CAPELA SANTO CARACAPPA FRANCISCO COLLANTES CLAUDIO DE LIBERATO JUAN A. DELGADO ERIC DENISON GEORGI GEORGIEV MEDHI EL HARAK STEPHAN DE LA ROCQUE YOUSSEF LHOR JAVIER LUCIENTES OLGA MANGANA MIGUEL ANGEL MIRANDA NEDELCHO NEDELCHEV KYRIAKI NOMIKOU AYKUT OZKUL MICHAEL PATAKAKIS ISABEL PENA PAOLA SCARAMOZZINO ALESSANDRA TORINA DAVID J. ROGERS 《Journal of Applied Ecology》2007,44(6):1231-1242
77.
The number of tumours developing on primary pinto bean leaves(Phaseolus vulgaris L. variety Pinto) inoculated with Agrobacteriumtumefaciens (Smith and Town.) Conn, strain B6, was increasedby as much as 100 per cent through the addition of several plant-growthfactors and antagonists of some of these factors to the freshlyinoculated leaves. Naphthylacetic acid, gibberellic acid, (2-chloroethyl)trimethylammonium chloride, and adenine gave a biphasic responsewith optimal promotions of tumour initiation at 10-5 to 10-4mg/ml. Tri-iodobenzoic acid and 4-chlorophenoxyisobutyric acidwere most active at 10-1 mg/ml. Mean tumour diameter showeda direct correlation with tumour number in these experiments.The results show tumour initiation to be sensitive to growthfactor changes, possibly through a heightened traumatic responseof the wounded leaves. The growth of the tumours was unaffectedby these additions except as they altered tumour number andthis secondarily affected tumour growth. 相似文献
78.
A statistical method for analyzing sensory profiling data obtained by means of fixed vocabulary or free choice profiling is discussed. The most interesting feature of this method is that it involves only simple statistical treatment and can therefore be performed using standard software packages. The outcomes of this method are compared to those of Generalized Procrustes Analysis on the basis of two data sets obtained, respectively, by means of fixed vocabulary and free choice profiling. A significance test is also discussed in order to assess whether the overall configuration of the products is meaningful. This significance test is based upon a simulation study involving the permutation procedure. 相似文献
79.
80.
The vegetative growth of Dactylis glomerata L. in sand was studiedunder controlled light, temperature, and nutritional conditions.Plants were daily supplied with three nutrient solutions ofdifferent nitrate concentrations (102, 103 and2 x 104 mol I1). For each concentration, growthobeyed an exponential law between the fourth and seventh weeksafter sowing. The time constant of the exponential was the samefor the shoot as for the root, and showed no significant variationwith nitrate concentration. The kinetic results and the strong dependence of the root: shootratio on nitrate concentration are discussed on the basis ofThornley's model. Hypothesizing that the molecular mechanismsof nitrate absorption are independent of the nitrate concentrationof the nutrient solution, we derived a relationship betweenthe root: shoot ratio and nitrate concentration. This relationshipwas found to be compatible with the experimental results. Dactylis glomerata L., vegetative phase, kinetics of growth, root: shoot equilibrium, nitrate absorption 相似文献