Ad libitum feeding plant systems fitted with two reservoirs were used to monitor daily aqueous uptake by plants from paired reservoirs. When the reservoirs contained aqueous solutions of the same chemical composition, a plant accepted nourishment from alternate sources without bias; but when the reservoirs contained different aqueous solutions, i.e. either tap water or standard nutrient solution, a sharp bias was exhibited, depending on the plant\u27s need for mineral nutrient, which changed with time. Eventually a stable-end-state was attained, favoring water over the standard nutrient solution in the ratio of 3 to 1. When the plant was pruned severely, however, preference oscillated sharply from one source to the other for six months while new growth developed to reestablish the stable-end-state . If a toxic pollutant was added to the favored reservoir, the plants preference switched sharply to the other source until the toxicant was eliminated from. the polluted reservoir, thus ensuring the plants survival
