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 Web of Science 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 Web of Science (12) Citing Articles via Google Scholar Google Scholar Articles by Bravo-F, P. Articles by Uribe, E. G. Search for Related Content PubMed PubMed Citation Articles by Bravo-F, P. Articles by Uribe, E. G. Agricola Articles by Bravo-F, P. Articles by Uribe, E. G.

Articles

An Analysis of the Relationship between Respiration and the Transmembrane Potential in Corn Roots ^1,2

Department of Botany, Washington State University, Pullman, Washington 99164

The effects of cyanide, anoxia, and temperatures varying from 2 to 42 C on the cell membrane electropotential difference (PD) of washed and freshly excised corn roots have been determined. Respiration rates of freshly excised root segments in response to cyanide and to varying temperatures were also measured. The cell membrane PD of roots which had been washed for 12 to 15 hours was almost insensitive to cyanide and anoxia but sensitive to low temperature. In contrast, the cell membrane PD of freshly excised roots was reversibly depolarized by all three treatments, cyanide depolarized from –117 to –86 millivolts and the sequential imposition of anoxia further lowered the PD to –69 millivolts. Anoxia applied first depolarized maximally and the PD was not further lowered by sequential cyanide treatment. Arrhenius plot analysis of the temperature response of respiration showed an apparent transition at 13 C with an activation energy of 20.0 kilocalories per mole below and 8.8 kilocalories per mole above the transition temperatures. The energy of activation for repolarization of PD is much higher; 53.4 kilocalories per mole below 7 to 8 C and 25.4 kilocalories per mole above this apparent transition. The energy requirement for polarization of the cell membrane PD was calculated based on the temperature responses of the cell membrane PD and respiration. It was estimated that 3.5% of the energy output from respiration at 22 C is required for cell polarization. It is unlikely that ion transport is limited by energy availability below the 8 C transition in this chill sensitive species.

¹ Partially supported by a grant from the Universidad Central de Venezuela to P. B.-F.

² This paper is dedicated to the memory of Professor Noe Higinbotham our dear friend and valued mentor in research.