Oxygen transfer characteristics in the compact callus aggregates of Rhodiola sachalinensis

The effective diffusivity of oxygen in compact callus aggregates (CCA) of Rhodiola sachalinensis was extremely small, varying from 0.34 x 10(-11) to 5.4 x 10(-9) m2/s and increasing with particle diameter. The calculated results indicated that severe oxygen limitations occurred in the CCA aggregates. However, the direct determination of the viability of the cells demonstrated that the CCA aggregates contained a high fraction of viable cells. It was suggested that the tissue differentiation or plasmodesmata within the CCA aggregates may provide capillaries for improving transport of oxygen and other nutrients.