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 Ullrich-Eberius, C. I. Articles by Ball, E. Search for Related Content PubMed PubMed Citation Articles by Ullrich-Eberius, C. I. Articles by Ball, E. Agricola Articles by Ullrich-Eberius, C. I. Articles by Ball, E.

Articles

Effect of Cyanide in Dark and Light on the Membrane Potential and the ATP Level of Young and Mature Green Tissues of Higher Plants ¹

Institut für Botanik, Technische Hochschule Darmstadt, D-6100 Darmstadt, Federal Republic of Germany, Department of Plant Pathology, University of Missouri, Columbia, Missouri 65211

The effect of CN^– and N₂ on the electrical membrane potential (E_m) was compared with that of CN^– on the ATP levels in cotyledons of Gossypium hirsutum and in Lemna gibba L. In mature cotton tissue, CN^– depolarized E_m to the energy-independent diffusion potential (E_D) in the dark. In the light E_m recovered transiently. The same was observed in leaves of Nicotiana, Avena, Impatiens, Kalanchoë, and in Lemna. In contrast, in young cotton cotyledons and tobacco leaves and, to a large extent, in +sucrose-grown Lemna, E_m was depolarized to E_D also in the light in a similar way as in the dark.

In Lemna grown without sucrose, the energy-dependent component of E_m was only partially depolarized by CN^– in dark or light. Cyanide plus salicylhydroxamic acid completely reduced E_m to E_D, abolished respiration and photosynthesis, and severely diminished the ATP level. This suggests the operation of a CN^–-insensitive respiration in uninjured Lemna. The initial CN^–-induced decay of the ATP level in cotton and Lemna was more rapid than the decay of E_m. CN^–-induced oscillations of the ATP level were followed by similar but slower oscillations of E_m. This supports the view of a general dependence of E_m on ATP. Discrepancies between inhibitor-induced changes of E_m and ATP levels are suggested to result from additional regulation of E_m by the cytoplasmatic pH value.

A comparison of E_D in young and mature cotton cotyledons in the dark and in the light suggests that in growing young cotyledons the different effect of CN^– in the light is due to a less effective photosynthesis together with high mitochondrial respiration. In Lemna and in mature cotton tissue, E_m in the light is maintained by noncyclic photophosphorylation and photosystem II, which is only partly inhibited by CN^–, thus resulting in an incomplete depolarization and recovery of E_m. Complete inhibition of photosynthetic O₂ evolution and membrane depolarization by CN^– plus salicylhydroxamic acid are suggested to result from photooxidation.