Measuring uncoupled oxygen uptake rate (OUR) could provide a convenient method for quantifying changes in the metabolic activity of plant cultures caused by hydrodynamic shear. Experiments on Daucus carota (carrot) cells were performed in a novel O-2-permeable Couette viscometer at varying levels of laminar shear (6 to 100 N m(-2)). When the uncoupled OUR of the cells was compared with mitochondrial activity (determined by 2,3,5-triphenyl tetrazolium chloride assay), a significant correlation was observed (R=0.91 by linear regression).