Stimulation of Weak Acid Uptake and Increase in Cell Sap pH as Evidence for Fusicoccin- and K+-Induced Cytosol Alkalinization 1
AUTOR(ES)
Marrè, Maria Teresa
RESUMO
In maize root segments fusicoccin induced a consistent increase in cell sap pH (taken as representative of vacuolar pH). This effect was markedly enhanced by the presence of K+ in the medium, whereas in the absence of fusicoccin K+ did not significantly influence cell sap pH. Treatment with a weak acid at 2 mm concentration inhibited the uptake of a different (14C-labeled) weak acid fed at a lower concentration, thus suggesting that acidification of the cytoplasm inhibits weak acid uptake. Fusicoccin and K+ increased the rate of uptake of 5,5-dimethyloxazolidine-2,4-dione, butyric acid, or isobutyric acid slightly when fed separately, strongly when fed in combination. The synergism between fusicoccin and K+ in stimulating weak acid uptake was parallel to that observed for the stimulation of H+ extrusion. Application of the weak acid distribution method to a condition of `quasi-equilibrium' indicated that fusicoccin induces a cytosolic pH increase of about 0.14 unit. These results are interpreted as providing circumstantial evidence that fusicoccin- and K+- induced stimulation of H+ extrusion led to an alkalinization of the cytosol, and that other early metabolic responses, such as an increase in malate level, are a consequence of the increase in cytosolic pH.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1056110Documentos Relacionados
- Bicarbonate-Induced Alkalinization of the Xylem Sap in Intact Maize Seedlings as Measured in Situ with a Novel Xylem pH Probe1
- The Simultaneous Determination of Muscle Cell pH Using a Weak Acid and Weak Base
- Cytoplasmic pH mediates pH taxis and weak-acid repellent taxis of bacteria.
- Effect of H+ Excretion on the Surface pH of Corn Root Cells Evaluated by Using Weak Acid Influx as a pH Probe 1
- Xylem Sap pH Increase: A Drought Signal Received at the Apoplastic Face of the Guard Cell That Involves the Suppression of Saturable Abscisic Acid Uptake by the Epidermal Symplast.