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51.
J. S. Bailey 《Plant and Soil》1992,143(1):19-31
Solution culture studies have shown that plant uptake of NH4
+ and NO3
- can be improved by increasing the concentration of Ca2+ in the root environment: the same may be true for grass grown in soil culture. An experiment was set up to see whether gypsum (CaSO4 2H2O) increased the rate at which perennial ryegrass absorbed 15NH4
+ and 15NO3
- from soil.The results demonstrated that gypsum increases the rates of uptake of both NH4
+ and NO3
- by perennial ryegrass. However because there was little potential for mineral-N loss from the experimental system, either by gaseous emission or by N immobilization, long term improvements in fertilizer efficiency were not observed. Nitrogen cycling from shoots to roots commenced once net uptake of N into plants had ceased. Labelled N transferred thus to roots underwent isotopic exchange with unlabelled soil N. It was suggested that this exchange of N might constitute an energy drain from the plant, if plant organic N was exchanged for soil inorganic N. The fact that the exchange occurred at all cast doubt on the suitability of the 15N-isotope dilution technique for assessing fertilizer efficiency in medium to long term experiments. There was evidence that the extra NO3
--N taken up by plants on the all-nitrate treatments as a result of gypsum application, was reduced in root tissue rather than in shoots, but to the detriment of subsequent root growth and N uptake. 相似文献
52.
Net fluxes of Ca2+, H+ and K+ were measured from intact Chara australis cells and from isolated cell walls, using ion-selective microelectrodes. In both systems, a stimulation in Ca2+ efflux (up to 100 nmol m?2 s?1, from an influx of ~40 nmol m?2 s?1) was detected as the H+ or K+ concentration was progressively increased in the bathing solution (pH 7.0 to 4.6 or K+ 0.2 to 10mol m?3, respectively). A Ca2+ influx of similar size occurred following the reverse changes. These fluxes decayed exponentially with a time constant of about 10 min. The threshold pH for Ca2+ efflux (pH 5.2) is similar to a reported pH threshold for acid-induced wall extensibility in a closely related characean species. Application of NH4+ to intact cells caused prolonged H+ efflux and also transient Ca2+ efflux. We attribute all these net Ca2+ fluxes to exchange in the wall with H+ or K+. A theoretical treatment of the cell wall ion exchanges, using the ‘weak acid Donnan Manning’ (WADM) model, is given and it agrees well with the data. The role of Ca2+ in the cell wall and the effect of Ca2+ exchanges on the measured fluxes of other ions, including bathing medium acidification by H+ efflux, are discussed. 相似文献
53.
Vertical profiles were measured in soil cores taken from flooded rice fields in the Po valley during July and August 1990.
Methane concentrations generally increased with depth and reached maximum values of 150–500 μM in 5–13 cm depth. However,
the shape of the profiles was very different when studying different soil cores. The CH4 content of gas bubbles showed a similar variability which apparently was due to spatial rather than temporal inhomogeneities.
Similar inhomogeneities were observed in the vertical profiles of acetate, propionate, lactate, and formate which showed maximum
values of 1500, 66, 135, and 153, μM, respectively. However, maxima and minima of the vertical profiles of the different substates
usually coincided in one particular soil core. Large inhomogeneities in the vertical profiles were also observed for the rates
of total CH4 production, however, the percentage contribution of H2/CO2 to CH4 production was relatively homogeneous at 24 ± 7% (SD). Similarly, the H2 content of gas bubbles was relatively constant at 93.3 ± 9.6 ppmv when randomly sampled in the rice field at different times
of the day. A small contribution (6%) of H2/CO2 to acetate production was also observed. Vertical profiles of the respiratory index (RI) for [2-14C] acetate showed that acetate was predominantly degraded by methanogenesis in 5–11 cm depth, but by respiration in the surface
soil (3 cm depth) and in soil layers below 13–16 cm depth which coincided with a transition of the colour (grey to reddish)
and the physical characteristics (porosity, density) of the soil. The observations indicate that the microbial community which
degrades organic matter to CH4 is in itself relatively homogenous, but operates at highly variable rates within the soil structure.
Author for correspondence 相似文献
54.
David I. Dunstan Debbie P. Lashta Susan I. Kikcio Trevor A. Thorpe 《In vitro cellular & developmental biology. Plant》1992,28(1):33-38
Summary The effects of sucrose concentration, addition of ammonium nitrate, and exposure to N6-benzyl-adenine (BA) on multiplication potential with shoots derived from shoot cultures of 17- to 20-yr-old Douglas fir trees
[Pseudotsuga menziesii (Mirb.) Franco] were compared. Each of these conditions, when compared independently, affected recurrent shoot multiplication
and influenced shoot development, as measured by the abundance of shoot apices. Sucrose concentration was influential, the
use of 25 g · liter−1 providing twice the multiplication obtained with 20 g · liter−1, and 14 × that obtained with the 30 g · liter−1 concentration routinely used (tree 11). Ammonium nitrate usage also improved multiplication, a 2.5 times improvement being
obtained after incorporation of 100 mg · liter−1 NH4NO3 into the medium (tree 33). Shoot cultures were responsive but relatively sensitive to addition of BA, the best improvement
in multiplication (5 times) being obtained with brief exposures to 3 mg · liter−1 BA (tree 11). Although shoot cultures were responsive to the conditions investigated, differences in shoot multiplication
and development were not displayed for several weeks. It was not possible therefore to repeat all the treatments with more
than one genotype; however, when this was possible a genotype-dependent variation in response was evident. 相似文献
55.
C. Tonini G. Cassani P. Piccardi S. Maini P.L. Castellari E. Pasqualini 《Journal of insect physiology》1982,28(5):443-446
Female-tip washings of the leafroller moth, Pandemis cerasana, were found to contain (E)-11-tetradecenyl acetate, (Z)-11-tetradecenyl acetate, (E)-11-tetradecenol, (Z)-11-tetradecenol and tetradecyl acetate, based on chemical analysis and electroantennogram tests. The relative amounts of these compounds in the gland were ca. 64:21:10:3:2 in the order named. Only (E)-11 and (Z)-11-tetradecenyl acetate were required for attraction of males to trap dispensed in the ratio 3:1, respectively. 相似文献
56.
The influence of various c oncentrations of K⁺, nitrogen sources, and inoculation with root-knot nematode Meloidogyne javanica were evaluated in tomato plants. Increased potassium concentration increased top and root fresh weights of intact plants and fresh weights of excised roots. Nitrate-fertilized plants weighed more than plants receiving ammonium independent of the K level in the medium. Nematode counts on roots were not affected by nutritional differences in intact or excised roots. In intact roots a high percentage of males was recorded at low K⁺ levels, whereas in excised roots the proportion of males in the population rose as the K⁺ levels increased. Inoculated intact roots accumulated K⁺ when the level of potassium supply was low; infected excised roots contained less K⁺ than did nematode-free roots. 相似文献
57.
Summary Mineralization of soil nitrogen studies with two acid sulfate soils under anaerobic and aerobic incubation at 30°C for 2 weeks showed that the mineral N was released and accumulated entirely as NH
4
+
in both soils. Nitrification did not occur in either of the soils under conditions that stimulate nitrification. The acid sulfate soils studied release good amounts of mineralizable N, and, because of lack of nitrifying activity, denitrification may not be a serious problem in these soils. 相似文献
58.
Investigation of the North American species Psilostrophe villosa afforded, in addition to known compounds, five new sesquiterpene lactones, which all turn out to be modified pseudoguaianolides, most of them closely related to hymenolide. However, one of the lactones is a new type of nor-pseudoguaianolide. Furthermore a new monoacetylated borneol-β-D-glucoside is present. The chemotaxonomic situation is discussed briefly. 相似文献
59.
Abstract Effect of ammonium on in vivo activity of nitrate reductase in roots, shoots and leaves of maize (Zea mays L.) seedlings was studied in relation to light/dark conditions and EDTA supply. Supply of 5 mM (NH4)2SO4 increased the steady state level of enzyme only in leaves and in light, while it had no effect in roots and shoots and in the dark. The substrate induction of enzyme was also little affected by 1 to 10 mM (NH4)2SO4 in roots and shoots. In the leaves the activity in the dark was either inhibited (minus EDTA) or stimulated (plus EDTA) by 5 to 10 mM (NH4)2SO4. The activity was stimulated in the light also in the presence of EDTA at higher concentrations of ammonium. When different concentrations of ammonium were supplied without any exogenous nitrate in the light, the enzyme activity increased at low concentration and was either inhibited or unaffected at higher concentrations depending upon the tissue used. Supply of EDTA with ammonium modified its effect to some extent. It is suggested that the effect of ammonium on nitrate reductase activity depends upon the tissue used and the effective concentration of the ammonium. 相似文献
60.
Biological activity of the antitumor protein neocarzinostatin coupled to a monoclonal antibody by N-succinimidyl 3-(2-pyridyldithio)-propionate 总被引:6,自引:0,他引:6
Gundram Jung Wolfgang Köhnlein Gerd Lüders 《Biochemical and biophysical research communications》1981,101(2):599-606
The chromophore free apoprotein of neocarzinostatin was coupled to monoclonal IgG1 antibody using N-Succinimidyl 3-(2-pyridyldithio)-propionate as heterobifunctional reagent. After coupling active chromophore was reassociated with the apoprotein. We present here experimental evidence that the hybrid protein retains biological activity as measured by the degradation of T2-DNA and bacteriostatic action. 相似文献