Uptake and Release of Abscisic Acid by Isolated Photoautotrophic Mesophyll Cells, Depending on pH Gradients
AUTOR(ES)
Kaiser, Werner M.
RESUMO
Uptake and release of abscisic acid (AbA) by isolated mesophyll cells of Papaver somniferum is characterized by the following observations: (a) Uptake rate is a linear function of the external AbA concentration in the range from 10−6 to 5 × 10−5 molar, and decreases with increasing pH. At any pH, uptake rate is linearly related to the concentration of undissociated abscisic acid, calculated from the pK = 4.7 according to the Henderson-Hasselbalch equation. At low external pH (5.0), AbA accumulation in the cells is about 10-fold. (b) Uptake of AbA is completely inhibited by salts such as KNO2 or sodium acetate, which decrease the pH gradient between medium and cells. KCN or m-chlorocarbonylcyanide phenylhydrazone inhibits AbA uptake only after longer incubation periods (20-40 minutes). (c) Uptake rate as well as equilibrium concentration is significantly higher in light than in darkness. (d) At low external pH, release of AbA from preloaded cells is strongly stimulated by KNO2. It is concluded that AbA is distributed between leaf cells and free space according to pH gradients, with the undissociated abscisic acid being the main penetrating species. Uptake and release occur via diffusion, without participation of a carrier.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=425916Documentos Relacionados
- Effects of auxin and abscisic acid on cytosolic calcium and pH in plant cells.
- Proton pumping and the internal pH of yeast cells, measured with pyranine introduced by electroporation.
- The Effect of pH, O2, and Temperature on the CO2 Compensation Point of Isolated Asparagus Mesophyll Cells 1
- Effect of pH and Auxin on Chloride Uptake into Avena Coleoptile Cells 1
- Measurement of the Effects of Acetic Acid and Extracellular pH on Intracellular pH of Nonfermenting, Individual Saccharomyces cerevisiae Cells by Fluorescence Microscopy