Abstract
Water permeability of plant cells has been recognized as an important factor which affects water pathway and hydraulic conductance inside of a plant body. Since plant cells develop large central vacuoles, plasma membranes (PM) and vacuolar membranes (VM) limit intra-cellular and trans-cellular water flow. Discovery of aquaporins has drawn our attention to how plants regulate water transport across PM and VM to optimize water status inside of the plant. To answer this problem, we developed a method for measuring osmotic water permeability of PM (Pf1) and VM (Pf2). In radish root protoplasts, bulk water permeability of single protoplast was 360 μms-1 (sd=90, n=10), and Pf2 was 590 μms-1 (sd=130, n=8). They are ranked at the highest level in plant cells. Pf1 level was also high as much as Pf2, but can be decreased to 10 % of the maximum level. Possible involvement of aquaporin will be discussed.
