title: Cell wall pH and auxin transport velocity.
abstract: According to the chemiosmotic polar diffusion hypothesis, auxin pulse velocity and basal secretion should increase with decreasing cell wall pH.  Experiments were designed to test this prediction.  Avena coleoptile sections were preincubated in either fusicoccin (FC), cycloheximide, pH 4.0, or pH 8.0 buffer and subsequently their polar transport capacities were determined.  Relative to controls, FC enhanced auxin (IAA) uptake while CHI and pH 8.0 buffer reduced IAA uptake.  Nevertheless, FC reduced IAA pulse velocity while cycloheximide increased velocity.  Additional experiments showed that delivery of auxin to receivers is enhanced by increased receiver pH.  This phenomenon was overcome by a pretreatment of the tissue with IAA.  Our data suggest that while acidic wall pH values facilitate cellular IAA uptake, they do not enhance pulse velocity or basal secretion.  These findings are inconsistent with the chemiosmotic hypothesis for auxin transport.
authors.affiliation: Department of Botany, San Diego State University, California 92182, USA.
authors.forename: K H
authors.initials: KH
authors.lastname: Hasenstein
authors.forename: D
authors.initials: D
authors.lastname: Rayle
mesh_terms: D018554:Avena / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*; D001692:Biological Transport; D002473:Cell Wall / Q000737:chemistry; D018548:Cotyledon / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism; D003513:Cycloheximide / Q000494:pharmacology; D006027:Glycosides / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration / Q000187:drug effects; D007210:Indoleacetic Acids / Q000037:antagonists & inhibitors / Q000378:metabolism*; D010937:Plant Growth Regulators / Q000378:metabolism*; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology
chemical_list: D006027:Glycosides; D007210:Indoleacetic Acids; D010937:Plant Growth Regulators; D011500:Protein Synthesis Inhibitors; C007808:fusicoccin; C030737:indoleacetic acid; D003513:Cycloheximide