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Biomedical subjects

W S Pierce

Publications and source records attributed to W S Pierce.

At least 163 records · Page 9Linked to original sources
PubMed1971

Electrical potential differences in cells of barley roots and their relation to ion uptake.

Single cell electropotentials of barley (Hordeum vulgare L., cv. ;Compana') root cortex were measured at different external concentrations of KCl in the presence of Ca(2+). The roots were low in salt from seedlings grown on 0.5 mm aerated CaSO(4) solution. Thus, the conditions were equivalent to those used to define the dual mechanisms found with radioactive tracer-labeled ion uptake. In 0.5 mm CaSO(4) alone, there is an increase with time of cell negativity from about -65 millivolts 15 minutes after cutting segments to about -185 millivolts in 6 to 8 hours. Two possible hypotheses, not mutually exclusive, are offered to explain this aging effect: that cutting exposes plasmodesmata which are leaky initially but which seal in time, and that some internal factors, e.g., hormones diffusing from the apex, have a regulatory effect on the cell potential, an influence which becomes dissipated in isolated segments and permits the development of a higher potential difference. In any case changes in selective ion transport must be involved. The cell potentials at KCl concentrations above 2.0 mm are more negative than would be expected for a passive diffusion potential. It is suggested that this discrepancy may be due to an electrogenic pump or to a higher K(+) concentration in the cytoplasm than in the remainder of the cell, or perhaps to both. Whether there is a clear relationship between cell potential and mechanisms 1 and 2 of cation transport depends upon whether the cell potentials of freshly cut or of aged tissue represent the values relevant to intact roots.

Journal Article↗
PubMed1970

Compartments and Fluxes of K, NA, and CL in Avena Coleoptile Cells.

By the compartmental analysis method of MacRobbie and Dainty, and Pitman, estimates of K(+), Na(+), and Cl(-) concentrations and fluxes were obtained for the cytoplasm and vacuole of coleoptile cells of oat, Avena sativa L. cv. Victory. Double labeling was used in experiments with (42)K plus (22)Na and with (42)K plus (36)Cl in a complete nutrient solution. At the plasmalemma, according to the Ussing-Teorell flux ratio equation, Na(+) is pumped out and Cl(-) is actively transported inward. The results with K(+) are less conclusive, but it is probably pumped in. At the tonoplast there is an active inward transport of Na(+) and probably of K(+), but the status of Cl(-) is uncertain, depending upon whether there is an electrical potential difference between the cytoplasm and vacuole. The results suggest that ion selectivity resides mostly in the plasmalemma. Possible errors in the estimates and interpretations are discussed.

Journal Article↗