The Use of Hordeum Leaf Protoplasts to Study Non-osmotic Volume during Cell Development

Abstract

Summary Volume changes of barley ( Hordeum vulgare L. cv. Patty) protoplasts, isolated from different developmental regions of primary leaves of barley seedlings, were measured after incubation in a range of sorbitol concentrations of different osmotic potentials. The presence or absence of KCl in the external protoplast medium had no significant effect on protoplast volume changes in short or long-term incubations. In short-term incubations of 5 minutes, protoplasts prepared from the whole of the leaf blade behaved as osmometers and showed volume changes in response to changing external osmotic potential. In long-term incubations of 8 hours similar protoplasts showed further changes in volume suggesting that a regulation of volume had occurred. The non-osmotic volumes (NOV) of protoplasts from three different developmental regions of the primary leaf were estimated by observing the short-term volume changes. The protoplasts were incubated in sorbitol solutions of different osmotic potentials and the Boyle-van't Hoff relationship applied to the results. NOV s of 5000, 2400, and 800 μm 3 were obtained for protoplasts from 60–75, 15–30 and 0–5 mm respectively above the basal intercalary meristem of the primary leaf. Relative contributions of plastids and nuclei to NOV were compared to the developmental status of the cell. It is suggested that NOV may be a useful concept to reflect the developmental status of leaf cells.