This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via CrossRef Citing Articles via Google Scholar Google Scholar Articles by de Quintero, M. R. Articles by Hanson, J. B. Search for Related Content PubMed PubMed Citation Articles by de Quintero, M. R. Articles by Hanson, J. B. Agricola Articles by de Quintero, M. R. Articles by Hanson, J. B.

Articles

Reactions of Corn Root Tissue to Calcium ¹

Department of Plant Biology, University of Illinois, Urbana, Illinois 61801

Washing corn (Zea mays L.) root tissue in water causes loss of about one-third of the exchangeable Ca²⁺ over the first 10 to 15 minutes. Upon transfer to K⁺-containing solutions, the tissue shows a short period of rapid K⁺ influx which subsequently declines. Addition of 0.1 millimolar Ca²⁺ decreases the initial rapid K⁺ influx, but increases the sustained rate of K⁺ and Cl^– uptake. It was confirmed (Elzam and Hodges 1967 Plant Physiol 42: 1483-1488) that 0.1 millimolar Ca²⁺ is more effective than higher concentrations for the initial inhibition, and that Mg²⁺ will substitute.

The inhibition arises from a mild shock affect of restoring Ca²⁺. With 0.1 millimolar Ca²⁺ net H⁺ efflux is blocked for 10 to 15 minutes and the cells are depolarized by about 30 millivolts. However, 1 millimolar Ca²⁺ rapidly produces increased K⁺ influx and blocks net H⁺ efflux for only a few minutes; blockage is preceded by a brief net H⁺ influx which may restore and increase ion transport by reactivating the plasmalemma H⁺-ATPase.

Stimulation of electrogenic H⁺-pumping with fusicoccin eliminates the shock responses and minimizes Ca²⁺ effects on K⁺ influx. Fusicoccin also strongly decreases Ca²⁺ influx, but has no effect on Ca²⁺ efflux. Ice temperatures and high pH decreased Ca²⁺ efflux, but uncoupler and chlorpromazine did not.

It is suggested that the inhibitory and promotive actions of Ca²⁺ are manifested through decreases or increases in the protonmotive force.