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|Title:||Control of Passive Influx of Calcium in Corn Root Tissue (calcium-2+ Channels, Ion Transport, Voltage-Regulator, Injury, Cold Shock)|
|Author(s):||Rincon, Elizabeth Magaly|
|Department / Program:||Plant Biology|
|Degree Granting Institution:||University of Illinois at Urbana-Champaign|
|Subject(s):||Biology, Plant Physiology|
|Abstract:||The entry of Ca('2+) into corn (Zea mays L.) root cells is passive and through channels which appear to be voltage-regulated as in animal cells. Environment stresses or shocks such as low and high temperatures, wounding, low pH, or application of metabolic inhibitors which lead to depolarization of the cell potential, increase the passive entry of Ca('2+) to the cells. Voltage-control is lost upon severe injury, and the control is recovered by washing the tissue.
Hyperpolarization of the cells by washing or by fusicoccin (FC) reduces the passive influx of Ca('2+) into the tissue. It is proposed that the Ca('2+) channels of corn root cells open during depolarization and close during hyperpolarization of the cell potential.
The Ca('2+) that enters the cell in response to injury, may open K('+) channels and as a result K('+) leaks out of the cells. The electrogenic H('+)-pumping is blocked by cold or acid treatments in a fashion that can be bypassed by FC. Recovery of K('+) transport is also realized by FC; however, blocking the Ca('2+) channels by pretreating the corn root segments with La('3+) is more effective in protecting the K('+) transport system against the deleterious effects of low temperatures than FC.
Plant hormones do not affect the passive transport of Ca('2+) as expected for Ca('2+) entry through voltage-gated channels. In addition to this, membrane surface sulfhydryl-groups are not involved in the gating mechanism of the channels.
The efflux of Ca('2+) from the cells appears to be active. FC enhances Ca('2+) efflux in freshly cut root segments, but it does not do so in washed root segments. FC does stimulate Ca entry in severely injured tissue and the increased Ca('2+) may activate mechanisms for active Ca('2+) extrusion. In washed tissue with recovered voltage control of the channels hyperpolarization of the cells acts to decrease Ca('2+) influx and therefore the Ca('2+) extrusion remains unaltered.
Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1985.
|Date Available in IDEALS:||2015-05-14|