Growth and osmotic relationships were examined in quaking aspen plants subjected to osmotic moisture potentials from -0.5 to -15.5 bars, and light intensities from 900 to 3,600 foot-candles. Reductions in plant dry weight, as moisture stress increased, were related to reduced cell turgor pressure. Variations in light intensity apparently had little effect on the water potential of the leaves. As light intensity was decreased, however, cell turgor pressure also decreased. The results suggest that both reduced turgor pressure and reduced photosynthesis may be directly related to quaking aspen's inability to grow under conditions of low light intensities. Forest Sci. 17:79-82.