Abstract
We tried to separate rice protoplasts by their size groups using a Counterflow Centrifugal Elutriation, which is a kind of separation method for cells in an equilibrium of centrifugal force and flow rate. As a result, the protoplasts could be separate in three size groups, S size, M size, and L size. Comparing activities of cell division and transient expressions in each group, L size was the best at both of them. Therefore, we will be able to select excellent rice protoplasts with activities of cell division and transient expression using the Counterflow Centrifugal Elutriation.