Osmotic Stress as a Pregrowth Procedure for Cryopreservation 2. Water Relations and Metabolic State of Sycamore and Soybean Cell Suspensions

Addition of 6 per cent mannitol or sorbitol to liquid culture medium decreased the water potential (ψw) by −0.93 MPa (≡ 382 ± 7 mOsm kg−1 water). Sycamore cells grown to exponential phase in such media exhibited increased levels of total and soluble protein and respiratory activity, but decreased amounts of free proline. Soybean cells showed increased respiratory activity and free proline levels, but total protein levels remained unaffected. Soluble protein levels were reduced under sorbitol-induced stress. In both species osmotic stress had little effect on cell dry weight. Water relation studies indicate that sycamore cells are capable of much greater osmotic adjustment than soybean cells, and that mannitol uptake does not contribute significantly to that adjustment.