Oscillations in H+ and Ca2+ ion fluxes around the elongation region of corn roots and effects of external pH

• Published in: Plant physiology (Bethesda) 1997-01, Vol.113 (1), p.111-118
• Main Authors: Shabala, S.N. (University of Tasmania, Hobart, Tasmania, Australia.), Newman, I.A, Morris, J
• Format: Article
• Language: English
• Subjects: Biological and medical sciences; CALCIO; CALCIUM; Cell physiology; ECHANGE D'ION; EQUIPO DE LABORATORIO; Fundamental and applied biological sciences. Psychology; HIDROGENO; HYDROGENE; INTERCAMBIO IONICO; ION; IONES; MATERIEL DE LABORATOIRE; MEDICION; MESURE; METHODE; METODOS; Plant physiology and development; Plasma membrane and permeation; RACINE; RAICES; ZEA MAYS
• ISSN: 0032-0889; 1532-2548
• DOI: 10.1104/pp.113.1.111

Net fluxes of H+ and Ca2+ around the elongation region of low-salt corn (Zea mays L.) roots were measured using the microelectrode ion flux estimation (MIFE) technique. At pH 5.2 two oscillatory components were found. Fast, 7-min oscillations in H+ flux were superimposed on slow oscillations of about 1.5 h. Fast oscillations in Ca2+ flux showed a strong dependence on the H+ oscillations and were normally leading in phase by about 1 to 1.5 min. Both oscillatory components were strongly affected by external pH values. Preincubation for 20 h in buffered pH 4.0 solution suppressed the slow oscillatory component and caused huge H+ influxes in the elongation region. The fast oscillations were 8 times larger in amplitude and were slightly lengthened. Preincubation at pH 6.0 did not suppress the rhythmic character of the ion fluxes but it shifted the average H+ flux to greater efflux. The fast and slow oscillatory components of H+ flux seem to relate to biophysical and biochemical mechanisms of intracellular pH homeostasis, respectively. The origin of the Ca2+ flux oscillations is discussed in terms of the "weak acid Donnan Manning" model of cell wall ion exchanges