Abstract
A review is presented of recent investigations bearing on the origin and metabolism of nicotine and its accompanying alkaloids in the living tobacco plant. A rational basis is developed for the interpretation of environmentally induced fluctuations in the nicotine content of the tobacco leaf based on the demonstration that nicotine is produced solely in the root of the growing plant and that it is continuously translocated to the stem and leaves via the transpiration stream. The available data on the intermediary metabolism of the tobacco alkaloids are critically discussed, and a spec-ulatory survey of the position of nicotine in the physiological economy of the tobacco plant is given.