Transpiration, leaf conductance to water vapor, leaf water potential, and photosynthesis were examined during flower induction and at anthesis in cocklebur and soybean growing under carefully controlled temperature and photoperiod conditions. In both species, transpiration rate based on water loss from whole plants, water vapor conductance, and leaf water potential were not measurably affected by floral induction. There were small increases in leaf photosynthetic rate after photoperiodic induction, but these changes were small and not statistically significant. We did not observe the changes in plant water balance, before or at flowering, that have been reported by others.