Direct versus indirect effects of p‐chloromercuribenzenesulphonic acid on sucrose uptake by plant tissues: The electrophysiological evidence

Abstract

The short‐term effects of p‐chloromercuribenzenesulphonic acid (PCMBS) on the transmembrane potential difference (PD) of broad bean (Vicia faba L. cv. Aguadulce) cotyledon cells and on sugar beet (Beta vulgaris L. cv. Klein E.) leaf cells were studied by the electrophysiological method. These effects were compared with that of the permeant thiol reagents N‐ethylmaleimide and HgCl2. N‐Ethylmaleimide and HgCl2 markedly and rapidly depolarised the PD of all the material studied, while PCMBS caused either a slight depolarisation (cotyledon cells) or no depolarisation (leaf cells) during the first 30 min of treatment. In cotyledons, PCMBS markedly inhibited sucrose uptake (89%) and the sucrose‐induced depolarisation associated with the proton‐sucrose symport (67%), while it decreased the proton‐motive force only marginally (7%). It is concluded that during short treatments (30 min or less). PCMBS inhibits sucrose uptake directly by blocking the sucrose carrier, and not the proton pump. For longer treatments, indirect effects cannot be excluded.

Effect of Diclofop on the Membrane Potentials of Herbicide-Resistant and -Susceptible Annual Ryegrass Root Tips

“…Therefore, PCMBS does not depolarize the Em and, consequently, has little effect on the proton- motive force (15). A 15-min pretreatment with 0.5 mM PCMBS alone did not depolarize the cell membrane potentials of either DM-resistant or -susceptible biotypes (Fig.…”

“…The relatively impermeable thiol reagent, PCMBS, directly blocks the sucrose carrier protein but does not act directly on the proton pump (15). Therefore, PCMBS does not depolarize the Em and, consequently, has little effect on the proton- motive force (15).…”

The Control of Single-Celled Cotton Fiber Elongation by Developmentally Reversible Gating of Plasmodesmata and Coordinated Expression of Sucrose and K+ Transporters and Expansin

“…Table 1 shows that 14 C-sucrose uptake into fibers at 10 to 12 DAA was significantly slowed by PCMBS and EB, a nonpermeating sulfhydryl-group modifier and an inhibitor of plasma membrane H ϩ -ATPase, respectively (M'Batchi et al, 1986;Beffagna and Romani, 1988). The inhibitory effect was much reduced at 16 to 18 DAA and was undetectable at 5 to 6 DAA (Table 1).…”

Accumulation of photoassimilate by Peronospora viciae (Berk.) Casp. and leaves of Pisum sativum L.: evidence for nutrient uptake via intercellular hyphae

“…For experiments with PCMBS and "COj, replicate leaflets inoculated with the same suspension of P. viciae sporangia were given 1 of 5 treatments described below, before exposure tô^C Oj or ^^COg as appropriate. (i) Transient treatment with PCMBS: leaflets injected with solution of 50 mM MES (morpholinoethane sulphonic acid)/NaOH buffer at pH 5-8 (see Wyness & Ayres, 1987), 250 mM sorbitol and 0-5 mM PCMBS (see Giaquinta, 1979;M'Batchi et al, 1986); discs (5 mm diameter) immediately excised from water-soaked leaflets and floated on 5 cm^ MES buffer and sorbitol but without PCMBS for 30 min (see Maynard & Lucas, 1982) to allow PCMBS to diffuse from the discs.…”

“…selectively and permanently by binding to the sucrose carrier protein in plasma membranes of higher plants (Giaquinta, 1979;Delrot, Despeghel & Bonnemain, 1980;M'Batchi et al 1986;M'Batchi, Pichelin & Delrot, 1987). PCMBS also inhibits the transport of maltose and raffinose (but not hexoses), and probably all amino acids and peptides (Giaquinta, 1979;Reinhold & Kaplan, 1984;M'Batchi e?…”