AbstractExperiments to develop and evaluate internal water stress in bean plants were conducted in controlled environment chambers under constant light, air temperature, and air movement conditions. Humidity was not controlled, but varied only slightly. The plants were grown in solution temperatures ranging from 10.0 to 32.5C to induce plant water stress.Plant water stress, if it can be indicated by reduced water use and growth, occurred at 15.0C and lower solution temperatures. Leaf relative turgidity values were not greatly affected by treatments after the first day and measurements were not sufficiently sensitive to adequately evaluate differences in plant responses. Leaf sugar content increased with time for all treatments, but the greatest increases occurred at the low temperatures. Water use efficiency was increased by low solution temperatures, the increases being greater for top than for root production and greater for dry weight than for fresh weight.