Two watering systems used for growing minimally stressed plants are described. An aeroponics system, which relies on a mist of nutrient solution applied to roots without a root support medium, affords control over water availability and easy access to roots. A continuous circulation system, which constantly circulates nutrient medium, also provides control over water availability as well as control over pO2and stress duration in flooded plants. A comparison is made of the growth characteristics of plants grown in the two systems with those grown by traditional watering methods. The significance of watering prehistory to stress physiology experiments is discussed.