title: Role of chloride ions in the promotion of auxin-induced growth of maize coleoptile segments.
abstract: OBJECTIVE
  The mechanism of auxin action on ion transport in growing cells has not been determined in detail. In particular, little is known about the role of chloride in the auxin-induced growth of coleoptile cells. Moreover, the data that do exist in the literature are controversial. This study describes experiments that were carried out with maize (Zea mays) coleoptile segments, this being a classical model system for studies of plant cell elongation growth.
  
  
  METHODS
  Growth kinetics or growth and pH changes were recorded in maize coleoptiles using two independent measuring systems. The growth rate of the segments was measured simultaneously with medium pH changes. Membrane potential changes in parenchymal cells of the segments were also determined for chosen variants. The question of whether anion transport is involved in auxin-induced growth of maize coleoptile segments was primarily studied using anion channel blockers [anthracene-9-carboxylic acid (A-9-C) and 4,4'-diisothiocyanatostilbene-2,2'-disulphonic acid (DIDS)]. In addition, experiments in which KCl was replaced by KNO3 were also performed.
  
  
  RESULTS
  Both anion channel blockers, added at 0·1 mm, diminished indole-3-acetic acid (IAA)-induced elongation growth by ~30 %. Medium pH changes measured simultaneously with growth indicated that while DIDS stopped IAA-induced proton extrusion, A-9-C diminished it by only 50 %. Addition of A-9-C to medium containing 1 mm KCl did not affect the characteristic kinetics of IAA-induced membrane potential changes, while in the presence of 10 mm KCl the channel blocker stopped IAA-induced membrane hyperpolarization. Replacement of KCl with KNO3 significantly decreased IAA-induced growth and inhibited proton extrusion. In contrast to the KCl concentration, the concentration of KNO3 did not affect the growth-stimulatory effect of IAA. For comparison, the effects of the cation channel blocker tetraethylammonium chloride (TEA-Cl) on IAA-induced growth and proton extrusion were also determined. TEA-Cl, added 1 h before IAA, caused reduction of growth by 49·9 % and inhibition of proton extrusion.
  
  
  CONCLUSIONS
  These results suggest that Cl(-) plays a role in the IAA-induced growth of maize coleoptile segments. A possible mechanism for Cl(-) uptake during IAA-induced growth is proposed in which uptake of K(+) and Cl(-) ions in concert with IAA-induced plasma membrane H(+)-ATPase activity changes the membrane potential to a value needed for turgor adjustment during the growth of maize coleoptile cells.
authors.affiliation: Department of Plant Physiology, Faculty of Biology and Environmental Protection, University of Silesia, Jagiellońska 28, PL-40-032 Katowice, Poland.
authors.forename: Zbigniew
authors.initials: Z
authors.lastname: Burdach
authors.affiliation: Department of Plant Physiology, Faculty of Biology and Environmental Protection, University of Silesia, Jagiellońska 28, PL-40-032 Katowice, Poland.
authors.forename: Renata
authors.initials: R
authors.lastname: Kurtyka
authors.affiliation: Department of Plant Physiology, Faculty of Biology and Environmental Protection, University of Silesia, Jagiellońska 28, PL-40-032 Katowice, Poland.
authors.forename: Agnieszka
authors.initials: A
authors.lastname: Siemieniuk
authors.affiliation: Department of Plant Physiology, Faculty of Biology and Environmental Protection, University of Silesia, Jagiellońska 28, PL-40-032 Katowice, Poland waldemar.karcz@us.edu.pl.
authors.forename: Waldemar
authors.initials: W
authors.lastname: Karcz
mesh_terms: D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000494:pharmacology; D000873:Anthracenes / Q000494:pharmacology; D001692:Biological Transport / Q000187:drug effects; D018118:Chloride Channels / Q000037:antagonists & inhibitors; D002712:Chlorides / Q000378:metabolism / Q000494:pharmacology*; D018548:Cotyledon / Q000187:drug effects* / Q000254:growth & development; D006863:Hydrogen-Ion Concentration; D007210:Indoleacetic Acids / Q000378:metabolism*; D008564:Membrane Potentials / Q000187:drug effects; D010937:Plant Growth Regulators / Q000378:metabolism*; D011189:Potassium Chloride; D003313:Zea mays / Q000187:drug effects* / Q000254:growth & development
chemical_list: D000873:Anthracenes; D018118:Chloride Channels; D002712:Chlorides; D007210:Indoleacetic Acids; D010937:Plant Growth Regulators; D011189:Potassium Chloride; C010030:9-anthroic acid; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid
keywords: Anion channel blockers; Zea mays maize; auxin; cell growth; chloride uptake; coleoptile segments; elongation growth; membrane potential