Beiträge zur Physiologie der Alkaloide

Summary 1. Slices of the leaf petiole of Nicotiana rustica L. accumulate nicotine from a 10-3 molar solution. The kinetics of this process are composite. A rapid uptake proceeds during the first 15 minutes. During the following 5—6 hours the kinetics are of first order. This part of the uptake process is characterized by the experiments. During this period of time the main quantity of nicotine is accumulated. The energy of activation of the process is ca. 6 kcal/moles. This agrees with a process of passive permeation. 2. Uptake of nicotine is inhibited by salts (KCl, NaCI, 50 mM/I). Salts reduce the capacity for nicotine accumulation. Neither the uptake kinetics nor the energy of activation of the process are changed during the time period, characterized by first order kinetics. 3. A parallelism is described between inhibition of nicotine uptake and a depression of the negative cell membrane potential. This parallelism has been found under the action of salts or of dinitrophenol and azide.