Cation uptake

R. Welch, W. Norvell, S. Schaefer, J. Shaff, and L. Kochian, Induction of iron (111) and copper (11) reduction in pea Pisiim. sativum L.) roots by Fe and Cu status. Does the root-cell plasma Fe(lll) reductase perform a general role in regulating cation uptake Planta 190 555 (1993). 

Nutrient uptake. Nutrient uptake includes base cation uptake (BCU) and nitrogen uptake (Nu). BC uptake assigns annual average uptake of Ca2+, Mg2+ and K+. The data represent an annual net uptake in keq/ha/yr and storage in stems and branches calculated over rotation. This includes the nutrients in the biomass compartments that are expected to be removed from the site at harvest. 

Sverdrup, H., Warfvinge, P., Rosen, K. (1995). A model for the impact of soil solution Ca Al ratio, soil moisture and temperature on tree base cation uptake. Water, Air and Soil Pollution, 61, 365-383. 

P-type ATPases from eukaryotes, bacteria, and Archaea catalyse cation uptake and/or efflux driven by ATP hydrolysis. Bacterial P-type ATPases... 

Uptake measurements were made [16] at several oxide/solution ratios, reported as surface loading (SL) or m2 oxide surface/liter of solution, as PdCl, 2 concentration was increased and pH was held constant at the optimal value (Figure 6.10a). Each SL indeed indicated a plateau near the steric value [16], For Pt and Pd ammine cations, the maximum surface density over many oxides appears to be a close-packed layer, which retains two hydration sheaths representative results for PTA uptake over silica from a recent paper [19] are shown in Figure 6.10b. The physical limit of cationic ammine surface density thus appears to be 0.84 pmol/m2, or about 1 cationic complex/2 nm2. Cationic uptake, therefore, is inherently half of anion uptake in many cases. 

The rate of maximum cation uptake has been shown to be dependent upon maximum levels of organic acids in the root cells (119,120). The organic acids, such as citric and malic acids, are transported from the sites of photosynthesis by the phloem while the cations are transported to the leaves by the xylem. Brown and Chaney (120) have suggested that iron uptake into the plant will be dependent upon the citric acid content of the root cells. 

Because very large concentrations of dissolved CO2 develop in submerged soil, in spite of root respiration the CO2 pressure outside the root may be greater than that inside it, resulting in a flow of CO2 from the soil to the atmosphere through the aerenchyma. Net removal of CO2 by the root decreases the concentration of the acid H2CO3 near the root, and this may offset the acidity produced in oxidation and excess cation uptake. 

Fe(II) oxidation was comparable to that released from the roots to balance excess cation uptake. But in both soils the H+ generated in these two processes exceeded the acidification calculated from the pH profile and the soil pH buffer powers. This was possibly because of CO2 uptake by the roots and, in the Maahas soil, where acidity diffusion was fast because of the high pH and high CO2 pressure, because the acidification spread beyond the zone of soil analysed. 

It is at present still difficult to correlate the absolute intensity of the SHG with the number of cationic complexes at the membrane surface. Therefore, a quantitative discussion, showing how the permselective uptake of primary cations forming SHG active complexes into the membrane side of the phase boundary corresponds to the increase in the membrane potential, is not possible yet. Lipophilic derivatives of photoswitchable azobis(benzo-15-crown-5) were recently shown as a molecular probe to determine photoinduced changes in the amount of the primary cation uptake into the membrane phase boundary in relation to the photoinduced EMF changes under otherwise identical conditions. 

As a consequence of this structural information, the proposal was made that it would be reasonable to consider that the monomeric forms are involved in cation uptake and release in polar media, such exposure being at the surface of a membrane, but that the actual transfer in the medium of low dielectric constant (the lipid phase) would be the dimeric form.572... 

Some illustrative examples of transport of Mg2+, Mn2+ and Ca2+ in microbes will be given in this section, and particular attention paid to cation uptake during sporulation. A number of transport processes will be described, which illustrate well the value of cation-selective ionophores in the study of cellular physiology. Excellent reviews of earlier work are available. 177 1BU... 

Myocardial imaging under II Cation uptake in myocardium Chelating ditertiary phosphine or 20, 613, 614... 

Vaughan, D., and McDonald, I. R. (1976). Some effects of humic acid on the cation uptake by parenchyma tissue. Soil Biol. Biochem. 8,415-421. 

As if/ drives cation uptake and ApH becomes great An antiport Pi hydroxyl can make salts accumulate. 

In order to account for the near equivalence of anion and cation uptake it was assumed that K a Ka and Xh X h. 

In contrast to the permanent depression of membrane potential when Ca is accumulated in the absence of permeant cation, uptake in the presence of acetate or phosphate leads to only a transient drop in potential, similar to that seen during State 3. 

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