Controls on calcium ion fluxes in injured or shocked corn root cells: Importance of proton pumping and cell membrane potential |
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Authors: | Magaly Rincon John B. Hanson |
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Affiliation: | Botany Dept., North Carolina State Univ., Raleigh, NC 27695, USA.;Dept. of Plant Biology, Univ. of Illinois, Urbana, IL 61801, USA. |
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Abstract: | Passive influx of 45Ca2+ into non-growing corn root tissue ( Zea mays L.) was increased as a result of actions (cutting, rubbing, chilling, heating, acidifying) or agents (cyanide, uncouplers) known to depolarize the cell membrane, and was decreased by actions (washing) or agents (fusicoccin) known to hyperpolarize it. These responses indicate the presence of Ca2+ channels which are voltage controlled. If the injuries were extensive, however, voltage control was lost and hyperpolarization with fusicoccin was expressed by increased 45Ca2+ influx. Control could be regained by tissue washing, and millimolar levels of external Ca2+ would protect against loss of control. Influx of Ca2+ was strongly inhibited by La3+, but only weakly by verapamil. Intact roots showed greater cold shock sensitivity in maturing cells than in growing cells. We conclude that corn roots normally restrict Ca2+ influx by a mechanism linked to hyper-polarization of the plasmalemma. Calcium ions which enter cold-shocked tissue are partially extruded during the early phase of recovery by a process stimulated by fusicoccin and subject to uncoupling. |
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Keywords: | A23187 Ca2+/H+ exchange cold shock fusicoccin K+ uptake tissue washing |
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