Abstract: There is provided in accordance with the invention a method for filtering comprising the steps of: providing a filter assembly comprising a depth filter and at least one microporous membrane; determining an optimal fluid velocity of the filter assembly by the steps of: operating identical filter assemblies at different constant fluid velocities, each for a time duration which terminates when a given total pressure drop is reached thereacross; noting the total throughput for such time duration; and based on the total throughput for each of said different constant fluid velocities, establishing a functional relationship between fluid velocity and total throughput for said filter assembly; and operating the filter assembly at a constant fluid velocity which corresponds to a desired total throughput.

Abstract: Apparatus for plant cell tissue culture including a plant growth enclosure having a bottom surface formed of a porous material, a buoyant element, separate from the plant growth enclosure and arranged to be placed thereunder in a body of liquid for supporting the plant growth enclosure, and spacer apparatus associated with at least one of the plant growth enclosure and the buoyant element for maintaining a predetermined separation between the buoyant element and the porous material.