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251.
J. A. DE GREEF F. VEROUSTRAETE L. VAN WIEMEERSCH H. FREDERICQ 《Physiologia plantarum》1979,47(1):44-48
A mathematical analysis for fast changes of ethylene concentration in an open flow system (non-steady-state conditions) is presented and experimentally tested. In this way it becomes possible to determine true values of ethylene production in the minute range following physiological and environmental changes which influence ethylene evolution. By this procedure ethylene kinetics can also be compared in absolute values independent of flow rate and plant chamber volume. 相似文献
252.
We have compared the amino acid sequences of two low-molecular-weight avian apoproteins: apoVLDL-II from very low-density lipoproteins of hen plasma and apovitellenin I from hen egg yolk. The sequence of White Leghorn apoVLDL-II was derived from the nucleotide sequence of cloned apoVLDL-II DNA (Chan et al., 1980). The sequenator was used to determine the amino acid sequence of apovitellinin I from two breeds of hen (White Leghorn and Australorp). The sequences from the two breeds were not only identical, but they also completely matched the predicted sequence derived from the apoVLDL-II DNA sequence. The identity reported here establishes that this protein is transported intact from the blood to the egg yolk. 相似文献
253.
Photosynthetic induction in wheat protoplasts and chloroplasts. Autocatalysis and light activation of enzymes 总被引:1,自引:0,他引:1
Abstract Unlike wheat chloroplasts, wheat protoplasts showed a pronounced restoration of the induction phase after a short period of darkness. This difference was used to investigate the relative roles of light-induced reductive activation of enzymes and the auto-catalytic increase in the level of substrates in the control of the rate of photosynthesis during induction. Light activation and dark inactivation of ribulose 5-phosphate kinase, fructose 1,6-biphosphatase and NADP+-specific glyceraldehydephosphate dehydrogenase were measured. In this respect there was no appreciable difference between protoplasts and chloroplasts. In contrast, the level of photosynthetic intermediates remained constant in darkened isolated chloroplasts, but declined rapidly in chloroplasts isolated from darkened protoplasts. When fructose 1,6-bisphosphatase was pre-activated by treating protoplasts with dithiothreitol the lag was only slightly shortened. These results are discussed in terms of control of the rate of the photosynthesis during the lag by substrates rather than limitation imposed by activity of any of the enzymes measured. 相似文献
254.
Abstract. Cyperus longus L. , which has a widespread but disjunct distribution throughout Europe and extends northwards into Britain, was found to be a C4 species based upon its Kranz leaf anatomy, low CO2 compensation point and the labelling of malate as an early product of 14 CO2 fixation. The photosynthetic characteristics of C. longus are similar to many other C4 species with a high maximum rate of photosynthesis (> 1.5 mg CO2 m −2 s −1 ) and a relatively high temperature optimum (30–35°C), but unlike many C4 species the rate of photosynthesis does not decline rapidly below the optimum temperature and a substantial rate (0.6 mgCO2 m−2 s−1 )occursat 15°C. Leaf extension is very slow at 15°C and shows a curvilinear response to temperatures between 15 and 25°C. Leaves extend at a rate of almost 4 cm d−1 at 25°C. 相似文献
255.
Mitsumasa Okamoto Hideo Yamagishi 《International journal of biological macromolecules》1981,3(2):105-113
In a previous study, various intermediates in λ DNA packaging were visualized after lysis of λ-infected cells with osmotic shock and sedimentation through a sucrose formalin cushion onto electron microscope grids. Along this line, a systematic screening for intermediates accumulated in all head mutants available was performed. λA?-infected cells accumulate only empty spherical protein shells (petit λ) bound at an intermediate point along the DNA thread. In situ digestion experiments with restriction endonuclease EcoRI show that the petit λ-DNA complexes are formed at a fixed point on the DNA concatemer. In cells, however, most petit λ was not bound to DNA. In Fec? cells, which are defective in formation of concatemers but normal in head protein synthesis, most petit λ did not sediment onto the carbon film of the grid. In mutant, petit λ, partially full heads and empty heads with released DNA were observed. λFI?-infected cells also accumulate petit λ and partially full heads. The present studies suggest that protein pNu1 is required for complex formation between head precursors and DNA concatemers, for the initiation of DNA packaging, and I for the promotion of DNA packaging, and for stabilization of head structures. The results obtained with other head mutants involved in formation of mature proheads and head completion confirm earlier results obtained by different techniques. 相似文献
256.
Paul Nieuwenhuysen Julius Clauwaert 《Journal of biochemical and biophysical methods》1981,5(5):279-286
It is impossible to measure the diffusion coefficient of macromolecules directly and accurately by quasi—elastic light scattering, when aggregates cannot be eliminated from the solutions to be investigated. Nevertheless, a simple method can be applied to overcome this problem in many cases. Aggregates are separated from the monomeric macromolecules by rate-zonal sedimentation in a CsCl density gradient in a transparent centrifugation tube; the monomers are then located by laser light scattering intensity measurements; photon correlation spectroscopy of the scattered light finally yields their diffusion coefficient. The viscosity of aqueous CsCl solutions at different temperatures and concentrations allows a good separation by centrifugation and a low uncertainty in the reduction of the measured diffusion coefficient to standard conditions.The application of the method to eukaryotic large ribosomal subunits is described as an example. 相似文献
257.
Simulated phototropic curvatures caused by differential masking of the cotyledons of de-etiolated seedlings exposed to white light are unconnected with true phototropism. In Cucumis sativus L. and Helianthus annuus L. such curvatures result from a red-light-induced inhibition coming from the exposed cotyledon. True phototropic bending in these species under long-term exposure to fairly high irradiances (as in nature) is a response to blue light. It occurs even when cotyledons are completely covered. These results show that the cotyledons do not perceive the phototropic stimulus and need not be illuminated for phototropism to occur. 相似文献
258.
Laminaria longicrucis De la Pylaie took up exogenous nitrate under both summer and winter conditions. During July and August no NO3- was detected in the ambient water or in algal tissues although it was present in both in February. Discs (2.3 cm diam.) of thin blade tissue were incubated with NO3- at four temperatures, with and without illumination. Similar values Jor NO3- uptake were found for both summer and winter collected plants when measured in light at 0 C. An apparent K of 4–6 μM was recorded for both types of plants; the Vmax ranged from 7 to 10 μmol h-1 g-1 dry wt measured in ca. 1800 μW cm-2 of cool-white fluorescent light. Uptake rates at 5 C were 66%, and at 0 C 30% of those for controls run at 15 C. The alga scavenged NO3- from solutions <0.5 μM. Ammonia did not inhibit NO3- uptake. Antibiotic pretreatment reduced NO3- uptake by a maximum of 12%. Nitrite uptake was inhibited in proportion to the concentration of NO3- in the medium. 相似文献
259.
J. Ramus 《Journal of phycology》1978,14(3):352-362
Light absorption by two green seaweeds with similar photophysiology but different anatomies are compared: i) Ulva lactuca var. rigida (C. Ag.) Le Jolis, an optically translucent species of two cell layers both bearing chloroplasts; and, ii) Codium fragile subsp. tomentosoides (van Goor) Silva, an optically opaque species with a colorlelss medulla surrounded by a cortex of choloroplast-bearing utriclels. Thallus absorptance (fraction of incident light absorbed) was measured for various pigment contents. Absorptance by U. lactuca was dependent on pigment concentration in an exponential manner and never exceeded 0.6, whereas absorptance by C. fragile was independent of pigment concentration and always approached a balue of 1.0. Water in the medullary tissue of C. fragile is often of the utricles. The utricles appear to be “integrating spheres” enhancing the capture of incident light, aided by the wave-guide function of the thin peripheral layer of cytoplasm and a reflector function at their base. Photosynthitic performance for U. lactuca saturates at high light intensities and attenuates rapidly with decreasing intensities. In contrast, photosynthetic performance for C. fragile saturates at low light intensities and attenuates slowly with diminishing radiation. Extrapolated diel variation in photosynthesis shows that U. lactuca's anatomy is adaptive for high light intensity environments, whereas C. fragile's anatomy is adaptive for low light intensity environments. Both seaweeds fit into the ecological category of “fugitive” species, and compete in the Long Island Sound (Atlantic Ocean) rocky intertidal for free-space. Predictions are presented for relative species abundances along a monotonic gradient of light intensity. 相似文献
260.
C-glycosylflavone accumulation in Sandoz 6706-treated barley seedlings is a photocontrolled response
Sandoz 6706 pretreatment of white light grown barley seedlings causes a 60% increase in saponarin (6-C-glucosyl-7-O-glucosylapigenin) but a 300% increase in lutonarin (3′-hydroxysaponarin). Norflurazon has little effect on saponarin levels but is almost as effective as Sandoz 6706 in enhancing lutonarin net synthesis. Barley roots contain saponarin and lutonarin only after herbicide treatment. Mung bean seedlings respond to Sandoz 6706 by accumulating higher levels of rutin and delphinidin 3-glucoside. The results are discussed in relation to the site of action of the herbicides, the High Energy photoresponse, and control of flavonoid 3′-hydroxylation. 相似文献