Sensitivity to Dinitrophenol of Potassium Absorption in Carrot Root Tissue Cultures

Abstract

IN 1954, Steward and Millar¹ reported that the absorption of cæsium ions by carrot root tissue was inhibited by dinitrocresol, and that after tissues had been stimulated to rapid growth in the presence of coconut milk they were more sensitive to the inhibitor than were slowly growing cultures. Steward concluded that the rapidly growing tissues consisted mainly of meristematic cells while the slowly growing tissues comprised mainly vacuo-lated cells. On this assumption he explained the differing sensitivity to uncoupling agents of the tissue in its two conditions by the suggestion that salt absorption into the cytoplasm of plant cells is more dependent on oxida-tive phosphorylation than is the subsequent transfer of ions into vacuoles. The experimental data provided by Steward and Millar¹ and by Millar² in support of this important conclusion are, however, rather complicated and difficult to interpret. Furthermore, Arisz³ claimed that chloride absorption into the cytoplasm of Vallisneria leaf cells is less sensitive to dinitrophenol than is its accumulation into vacuoles. In view of these considerations, it seemed desirable to examine the situation further and we wish to report some observations on the sensitivity to dinitrophenol of potassium absorption in rapidly and slowly growing carrot tissue cultures.