DEVELOPMENT OF A FLUORESCENT TRACER TECHNIQUE TO EVALUATE MIXING IN PLANT-ROOT CULTURE

Liquid mixing times were measured in shake-flask root cultures based o n dispersion of a concentrated riboflavin solution. Microplate fluorim etry allowed rapid quantification of small sample volumes and permitte d mixing analysis in small vessels. An increase in mixing time from 2 min at a tissue concentration of similar to 150 g fresh wt/l to beyond 1 h at similar to 200 g fresh wt/l, as well as Fourier analysis of os cillatory mixing profiles, provided evidence for severe mixing impairm ent. Comparison of these mixing times to biological O-2 demand suggest ed that high density, shake-flask root cultures are severely O-2 limit ed due to impaired bulk liquid mixing.