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1.
Gibberellins in Embryo-Suspensor of Phaseolus coccineus Seeds at the Heart Stage of Embryo Development 总被引:2,自引:1,他引:1
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Gibberellins (GAs) in suspensors and embryos of Phaseolus coccineus seeds at the heart stage of embryo development were analyzed by combined gas chromatography-mass spectrometry (GC-MS). From the suspensor four C19-GAs, GA1, GA4, GA5, GA6, and one C20 GA, GA44, were identified. From the embryo, five C19-GAs GA1, GA4, GA5, GA6, GA60 and two C20 GAs, GA19 and GA44 were identified. The data, in relation to previous results, suggest a dependence of the embryo on the suspensor during early stages of development. 相似文献
2.
Level of Abscisic Acid in Integuments, Nucellus, Endosperm, and Embryo of Peach Seeds (Prunus persica L. cv Springcrest) during Development
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Free abscisic acid (ABA) in integuments, nucellus, endosperm, and embryo was determined throughout seed development of peach (Prunus persica L. cv Springcrest). Quantification of ABA was performed using combined high performance liquid chromatography-radioimmunoassay based on a monoclonal antibody raised against free (S)-ABA. In the integuments and endosperm, ABA concentration remained constant during the first 100 days after anthesis and rose in the following days when fresh weight was rapidly decreasing. In the nucellus, the ABA concentration variation pattern paralleled that of tissue growth. ABA concentration in the embryo increased constantly with the growth of the tissues to reach a maximum at the last growth stage. The role of ABA in peach seeds is discussed in relation to the development of the different seed tissues. 相似文献
3.
An nmr spectral comparison of a model cyclic pentapeptide cyclo(Gly-Pro-Gly-D-Phe-Pro) with an analogous pseudopeptide has been made. The pseudopeptide contains a ψ[CH2S] amide bond replacement at the only amide linkage that, in the model, is not involved in an intramolecular hydrogen bond. Both proton and carbon-13 nmr spectral evidence confirms the retention of β- and γ-turns in the pseudopeptide in chloroform. Characteristic chemical shifts, temperature dependence, and glycine α-resonances support this interpretation. However, evidence of a more flexible conformation involving cis–trans proline isomerism is seen on addition of dimethylsulfoxide. 相似文献
4.
Arnošt Pilát 《Folia Geobotanica》1969,4(3):225-234
The meadow plant communities,Arrhenatheretum elatioris alopecuretosum pratensis R. Tx. 1937 andMesobrometum erecti stipetosum Vicherek 1960, were chosen for investigations of the underground plant parts. Apparent differences in underground dry weight and its seasonal changes in both the communities were observed. Differences in the soil environment in different periods of the year are reflected in the character of time changes in underground dry weight. The soil environment affects not only the total underground biomass and their changes in time, but also the activity of soil microflora and, consequently, the decomposition rate of dead underground plant parts. 相似文献
5.
Jorge Florin-Christensen Monica Florin-Christensen Arno Tiedtke Leif Rasmussen 《Microbial ecology》1990,19(3):311-316
In an attempt to extend our knowledge of the biology of feeding of the ciliateTetrahymena thermophila, this organism was grown axenically on complex organic material. The nutrient substrate was based on autoclaved wheat grains and adjusted to either pH 5.5 or 7.5. In wild type cultures the cells grew and multiplied only under acidic conditions. In cultures of a mutant cell line blocked in the secretion of acid hydrolases the cells did not grow at either pH value. Thus released acid hydrolases may play a key role in the utilization of complex nutrients in combination with uptake of small organic molecules. Mechanisms in the feeding biology ofTetrahymena thermophila andParamecium tetraurelia are compared. 相似文献
6.
Stefania Canino Barbara Nieri Laura Pistelli Amedeo Alpi Luigi De Bellis 《Physiologia plantarum》1996,98(1):13-19
The activity of NADP+ -dependent isocitrate dehydrogenase (ICDH, EC 1.1.1.42) was investigated during the post-germinative growth of cucumber ( Cucumis sativus L. cv. Marketmore) seedlings. Isoelectric focusing showed the presence of several isoenzymes, two of which represented 70–80% of the total NADP+ -ICDH activity in cotyledons of seedlings grown in the dark. They had pI values between 4.8 and 5.8. The isoenzyme with higher pI was purified to homogeneity by hydrophobic interaction, affinity, hydroxylapatite and anion exchange chromatography. The purified isoenzyme is a dimeric protein, consisting of two apparently identical 43-kDa subunits. It is specific for NADP+ , inhibited by ATP and by 2-oxoglutarate, whereas it is not inhibited by citrate, succinate, and glyoxylate. The data indicate that NADP+ -ICDH from cucumber is structurally similar to ICDHs from other plants, but it shows some peculiar biochemical characteristics. 相似文献
7.
Piero Picciarelli Alberto Piaggesi Nello Ceccarelli Lorenzo Guglielminetti Amedeo Alpi 《Plant Growth Regulation》1994,14(2):183-185
Endogenous gibberellins (GAs) were extracted from suspensor, embryo and integument of very young seeds of Phaseolus coccineus L. and detected by combined gas chromatography-mass spectrometry (GC-MS). Results show the presence of one C20-GA, GA44 and five C19-GAs in the suspensor: GA1, GA4, GA5, GA6 and GA8, and four C19-GAs in the integument: GA1, GA5, GA6 and GA8. Only traces of GA1 and GA5 were identified in the embryo. A compound structurally related to GAs was identified as tetrahydroxy-Kauranoic acid in suspensor, integument and, only in trace amounts, in the embryo. 相似文献
8.
The solid state conformations of cyclo[Gly–Proψ[CH2S]Gly–D –Phe–Pro] and cyclo[Gly–Proψ[CH2–(S)–SO]Gly–D –Phe–Pro] have been characterized by X-ray diffraction analysis. Crystals of the sulfide trihydrate are orthorhombic, P212121, with a = 10.156(3) Å, b = 11.704(3) Å, c = 21.913(4) Å, and Z = 4. Crystals of the sulfoxide are monoclinic, P21, with a = 10.662(1) Å, b = 8.552(3) Å, c = 12.947(2) Å, β = 94.28(2), and Z = 2. Unlike their all-amide parent, which adopts an all-trans backbone conformation and a type II β-turn encompassing Gly-Pro-Gly-D -Phe, both of these peptides contain a cis Gly1-Pro2 bond and form a novel turn structure, i.e., a type II′ β-turn consisting of Gly–D –Phe–Pro–Gly. The turn structure in each of these peptides is stabilized by an intramolecular H bond between the carbonyl oxygen of Gly1 and the amide proton of D -Phe4. In the cyclic sulfoxide, the sulfinyl group is not involved in H bonding despite its strong potential as a hydrogen-bond acceptor. The crystal structure made it possible to establish the absolute configuration of the sulfinyl group in this peptide. The two crystal structures also helped identify a type II′ β-turn in the DMSO-d6 solution conformers of these peptides. © 1993 John Wiley & Sons, Inc. 相似文献
9.
Copper-Putrescine-Pyridine (Cu-PuPy) is a membrane-permeable complex which efficiently dismutates superoxide. In excess of 0.1 mM it is highly cytotoxic and oxidizes cellular GSH with concomitant production of H2O2. Here we show that treatment of CHO cells with 0.2 mM Cu-PuPy (0-200 min) leads to an accumulation of H2O2. Organic hydroperoxides which are also formed at low levels in the presence of Cu-PuPy, increase significantly after removal of the copper complex. We conclude that Cu-PuPy acts as an oxidant until cellular GSH is depleted. However, by interfering with radical chain propagation reactions, it suppresses lipid peroxidation and thus substitutes for consumed physiological antioxidants in a later stage of treatment. This consistently explains our previous, seemingly paradox, finding that longer Cu-PuPy treatments may be significantly less toxic than shorter ones. 相似文献
10.
The mechanism determining which parental haplotype is selected in (CBA × 1310) (k × b)F1 female mice for major histocompatibility complex (H-2) restricted, male-specific (H-Y), immune, cytotoxic T-cell (Tc-cell) responses, was investigated. The data show that haplotype preference is variable, and may be directed towards one, both, or neither of the parental haplotypes. This preference is reflected in the precursor frequency of memory Tc cells as measured by limiting dilution assays. It was further shown that maternal influence, antigen dose, route of immunization, and a feedback mechanism on the stimulator cells in vivo could not influence haplotype preference or its observed variability. Evidence for cross-reactive killing by H-2k and H-2b H-Y immune Tc cells on H-2b and H-2k allogeneic targets, respectively, (i. e., the independent haplotype of the other parent of the F1 mice), provide evidence for natural tolerance as a possible mechanism to explain haplotype preference. 相似文献