草莓愈伤组织超低温贮藏及植株再生研究

本文介绍了草莓愈伤组织的诱导,超低温贮藏及不同解融方法对其细胞存活率和芽分化的影响。     

Effects of temperature at constant air dew point on leaf carboxylation efficiency and CO2 compensation point of different leaf types

The effect of temperature on photosynthesis at constant water-vapor pressure in the air was investigated using two sclerophyll species, Arbutus unedo and Quercus suber, and one mesophytic species, Spinacia oleracea. Photosynthesis and transpiration were measured over a range of temperatures, 20–39° C. The external concentration of CO₂ was varied from 340 bar to near CO₂ compensation. The initial slope (carboxylation efficiency, CE) of the photosynthetic response to intercellular CO₂ concentration, the CO₂ compensation point (), and the extrapolated rate of CO₂ released into CO₂-free air (R _i) were calculated. At an external CO₂ concentration of 320–340 bar CO₂, photosynthesis decreased with temperature in all species. The effect of temperature on was similar in all species. While CE in S. oleracea changed little with temperature, CE decreased by 50% in Q. suber as temperature increased from 25 to 34° C. Arbutus unedo also exhibited a decrease in CE at higher temperatures but not as marked as Q. suber. The absolut value of R _i increased with temperature in S. oleracea, while changing little or decreasing in the sclerophylls. Variations in and R _i of the sclerophyll species are not consistent with greater increase of respiration with temperature in the light in these species compared with S. oleracea.Abbreviations and symbols A net photosynthetic rate - C and C _i CO₂ concentration in the air and in the intercellular airspace of the leaf, respectively - CE carboxylation efficiency - E transpiration rate - R _i CO₂ release into CO₂-free air estimated from extrapolation to 0 bar CO₂ - T _i leaf temerature - VPD difference in water-vapor pressure between mesophyll and air - CO₂ compensation point     

Efficient separation of subfossil Chironomidae from lake sediments

Electron transport system (ETS) activity, CO₂ evolution, O₂ consumption, N₂-fixation (C₂H₂ reduction) and methanogenesis were appropriately measured in aerobic and anaerobically incubated sediment at 4, 10 and 20 ° C to better characterize these activities under different incubation conditions. ETS activity was always higher in the aerobically incubated sediment at all three incubation temperatures, whereas (C₂H₂ reduction was always greater in the anaerobic sediment. Carbon dioxide evolution was detected only in the aerobic sediment at 10 and 20 ° C but not at 4 ° C. Methane evolution in anaerobic sediment increased gradually with an increase in the incubation temperature.     

Embryonic development times of entomostracan zooplankton from Lake le Roux (Orange River,South Africa), and their possible relationships to seasonal succession

Embryonic development times of the principal entomostracan zooplankton of Lake le Roux, Orange River, South Africa, are described. Durations decreased monotonically with temperature over the thermal tolerance range and are described using Blehrádek's equation. The present data are compared with other observations on rate-temperature responses of warm-water and temperate zooplankton. Small, but ecologically significant, differences are discerned. The possible significance of species-specific rate-temperature responses to the phenomenon of seasonal succession is explored.     

Immunochemical Characterization of Pyruvate Dehydrogenase Complex in Rat Brain

Pyruvate dehydrogenase complex (PDHC) in rat brain was studied immunochemically, using antibodies against the bovine kidney PDHC, by immunoblotting, immunoprecipitation, inhibition of enzyme activity, and enzyme-linked immunoabsorbent assay (ELISA). The immunoblots showed that the antibodies bound strongly to the alpha peptide of the pyruvate dehydrogenase (E1) component, and to the dihydrolipoyl transacetylase (E2) and the dihydrolipoyl dehydrogenase (E3) components of PDHC. A similar immunoblotting pattern was observed in all eight brain regions examined. On immunoblotting of the subcellular fractions, these PDHC peptides were observed in mitochondria and synaptosomes but not in the postmitochondrial supernatants. This agrees with other evidence that brain PDHC is localized in the mitochondria. These results, together with those from sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the immunoprecipitin, also showed that the alpha E1, beta E1, and E3 peptides of rat brain PDHC are very similar in sizes to those of the bovine kidney PDHC, being 42, 36, and 58 kD, respectively. The size of the E2 peptide, 66 kD, is different from that of bovine kidney E2, 73 kD. The relative abundance of PDHC protein in nonsynaptic mitochondria was compared by enzyme activity titration and ELISA. Both methods demonstrated that the amount of PDHC antigen in the mitochondria from cerebral cortex is greater than that in the olfactory bulb mitochondria. This is consistent with the results of the activity measurement. The ELISA also showed that the PDHCs in both mitochondrial populations are antigenically similar.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of temperature on ethylene biosynthesis in carnation petals

Carnation petals, at a stage in which they are already producing ethylene, show a sigmoidal dependency of ethylene production on temperature within the range of 0 to 30°C. An Arrhenius plot of these data show a break atca. 22°C in the straight lines connecting the points. The activity of the ethylene-forming enzyme (EFE), measured bothin vitro, using isolated membranes, andin vivo, using petals pretreated with 1-aminocyclopropane-1-carboxylic acid (ACC), shows an exponential dependency on temperature within the same range. Arrhenius plots of EFE activity fail to show any discontinuity.In contrast, ACC synthase activity measuredin vitro shows the same sigmoidal dependency on temperature as that of the intact petals. We suggest, therefore, that ACC synthase activity is the rate-limiting step mediating the influence of temperature on ethylene biosynthesis by carnation petals over the range studied.     

Satiety, hunger and regional brain content of cholecystokinin/gastrin and met-enkephalin immunoreactivity in sheep

Cholecystokinin (CCK) and met-enkephalin (MEK) related peptides have been shown to alter feeding behavior subsequent to their injection into the peripheral circulation or directly into the brains of several species. To evaluate the potential role of endogenous brain pools of these peptides in feeding, groups of sheep were sacrificed either immediately following a meal (satiated) or after various intervals of food deprivation (hungry). Content of CCK-gastrin immunoreactivity in the anterior hypothalami of satiated sheep was elevated compared to 2, 4, or 24 hours of food deprivation. Content of MEK increased progressively with longer intervals of fasting (4 and 24 hours) in the amygdala and basomedial hypothalamus, whereas olfactory bulb content decreased with a similar time course. The results support a potential role for anterior hypothalamic CCK/gastrin in behaviors of satiety, whereas MEK neurons of limbic/rhinencephalic regions appear to form part of a separate circuit gradually activated by increasing hunger. Results are discussed in terms of potential target regions of the peptides, as well as the regional levels and feeding response of sheep as compared to available data from other species.     

Physicochemical aspects of carbohydrate binding to some plant lectins with binding preference forN-acetylgalactosamine and galactose

This contribution illustrates the advantages of some chromophoric and fluorophoric carbohydrate derivatives such asp-nitrophenyl (pNO₂Phe) or 4-methylumbelliferyl (MeUmb) glycosides andN-dansylgalactosamine in studies of the binding equilibrium and kinetics with some plant lectins. The methods used involve continuous titrations of changes in ligand or protein absorption and ligand fluorescence, including substitution titrations as well as stopped-flow, temperature-jump or pressure-jump relaxation kinetics. When monitored by temperature-jump relaxation, binding of MeUmbαGal to the bloodgroup A specific lectin GSAI-A₄ fromGriffonia simplicifolia is a simple bimolecular association with parametersk ₊ = 9.4 × 10⁴ M^-1 s^-1 andk _-1 = 5.3 s^-1 at 23°C, but binding to the GSAI-B₄ lectin is biphasic. The complementarity of the peanut agglutinin binding site with Galβ1 → 3GalNAc that occurs in manyO-glycoproteins follows from enthalpic considerations and also from the value of the dissociation-rate parameterk _-1 = 0.24 s^-1 of the MeUmbβGalβl → 3GalNAc.lectin complex. This value, obtained by stopped-flow kinetics is 100 times smaller than for other mono-and disaccharides investigated. The binding mechanism is simple and the derivatisation of Galβ1 → 3GalNAc does not affect the affinity to a considerable degree. The binding preference of tetravalentsoybean agglutinin for MeαGalNAc over MeαGal by a factor of 25 is mainly of enthalpic origin with an additional 7 kJ mol^-1; the NAc group causes perturbation of a tryptophanyl residue, evidenced by protein difference absorption spectrometry. In the glycosides, a large aglycon likeβpNO₂ Phe orβMeUmb hardly affects the affinity of SBA but a largeN-dansyl group increases the affinity by a factor 20 as compared to GalNAc. The 10-fold increase in carbohydrate-specificN-dansylgalactosamine fluorescence, together with a very favourable entropic contribution point at the presence of a hydrophobic region in the vicinity of the carbohydrate-binding site. The dissociation-rate parameter of the MeUmbβGalNAc SBA complex is slower than for any reported monosaccharide-lectin complex: 0.4 s^-1. The divalent lectin fromErythrina cristagalli preferentially binds the Galβ1 → 4GlcNAc structure that occurs in manyN-glycoproteins. The combining site was mapped thermodynamically with carbohydrates ranging from mono-to pentasaccharides as derived fromN-glycoproteins. Here, N-dansylgalactosamine was used as a fluorescent indicator ligand in substitution titrations. When Galβ1 → 4GlcNAc was linkedα1 → 2 orα1 → 6 to Man, the binding enthalpy and entropy remained practically constant. Application of stopped flow kinetics and pressure-jump relaxation withN-dansylgalactosamine gave mono-exponential signal changes with a concentration dependence corresponding tok ₊ = 4.8 x 10⁴ M^-1 s^-1 k _- = 0.4 to 0.66 s^-1 and a change in reaction volume of+7ml/mol.     

Regulation of the loss of frost hardiness in Pinus radiata by photoperiod and temperature

Abstract. In controlled environments, the interactive effects of warm (16: 8°C, day: night) and cool (12: 4°C, day: night) temperatures and long (13.5 h) and short (10 h) photoperiods on the dehardening of seedlings of Pinus radiata D. Don were investigated. In another experiment, the effect of four photoperiods from 9 to 14 h was examined. In a third, dehardening at constant temperatures from 5 to 17°C was followed. There was no evidence for an interaction between photoperiod and temperature. Dehardening was temporarily delayed by photoperiods below about 10 h, but there was no other quantitative effect of photoperiod. At constant temperatures, the rate of dehardening was initially constant but declined as the minimum summer frost hardiness was reached. In the initial phase the rate of dehardening was a linear function of temperature, increasing from 0.05°C day⁻¹ at 8°C to 0.30 °C day⁻¹ at 17°C. Temperature controlled the loss of frost hardiness by regulating the rate of dehardening.