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Potassium-Ammonium Uptake Interactions in Tobacco Seedlings 总被引:6,自引:0,他引:6
SCHERER HEINRICH W.; MACKOWN CHARLES T.; LEGGETT J. EVERETT 《Journal of experimental botany》1984,35(7):1060-1070
Short-term (< 12 h) uptake experiments were conducted with67-week-old tobacco (Nicotiana tabacum L. cv. Ky 14)seedlings to determine absorption interactions between K+ andNH4+. At equal solution concentrations (0.5 mol m3) netK+ uptake was inhibited 3035% by NH4+ and NH4+ uptakewas decreased 924%. Removal of NH4+ resulted in completerecovery in K+ uptake rate, but NH4+ uptake rate did not recoverwhen K+ was removed. In both cases, inhibition of the uptakerate of one cation saturated as the concentration of the othercation was increased up to 0.5 mol m3. The relative effectof K+-NH4+ interactions was not altered when Cl- was replacedwith SO42, but the magnitudes of the uptake rates wereless in the absence of Cl-. The Vmax for NH4+ uptake was reducedfrom 128 to 105 µmol g1 dry wt. h1 in thepresence of 0.5 mol m3 K+ and the Km for NH4+ doubledfrom 12 to 27 mmol m3 in the presence of K+. The resultsof these K+-NH4+ experiments are interpreted as mixed-noncompetitiveinteractions. However, an enhanced efflux of K+ coupled to NH4+influx via an antiporter cannot be ruled out as contributingto the decrease in net K+ uptake. Key words: Nicotiana tabacum, K+, NH4+, Uptake interactions 相似文献
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Vocal fold geometry plays an important role in human phonation. The intraglottal quasi-steady pressure and velocity distributions
depend upon the shape, size, and diameter of the glottis. This study reports the effects of the variation of glottal shapes
on intraglottal pressures and velocities using a Plexiglas model with a glottis having nine symmetric glottal angles (uniform,
as well as convergent and divergent 5°, 10°, 20° and 40°), while the minimal glottal diameter was held constant at 0.06 cm.
The empirical data were supported by penalty finite element computational results. The results suggest that larger convergent
glottal angles correspond to increased pressures and decreased velocities in the glottis upstream of the minimum glottal location,
with a reversal of this pattern at the minimal glottal diameter location. The pressure dip near the glottal entrance for divergent
glottal angles was greatest for the 10° divergence angle condition, and was sequentially less for 5°, 20°, and 40°. Flow resistance
was greater for a convergent angle than a divergent angle of the same value, and least for the 10° divergent condition. Pressure
recovery in the glottis suggested that the optimal glottal diffuser angle was near 10°. Results suggest that the glottal geometry
has a critical relationship with phonation (especially for vocal efficiency), and therefore important significance to understanding
artistic voice and clinical voice management. 相似文献
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SCHERER J 《Acta anatomica》1955,23(4):350-379