Die Bodenkultur - Journal for Land Management, Food and Environment


A simplified pressure-volume method for the estimation of osmotic adjustment with the pressure chamber


A method for the estimation with a pressure chamber of osmotic potential (ψ 0) at known water saturation deficits in leaves is described and tested. The new approach is based on the concept of pressure-volume (PV) curve analysis and requires only one measurement of total water potential to be made at a water saturation deficit (WSD) value higher than the turgor loss point. The result may then be extrapolated to any other WSD. Advance knowledge of an average value for the x-intercept of the PV curve and of the maximum WSD of the turgor loss point in the material to be analyzed is required for this extrapolation. The method was tested on 170 PV curves from two varieties of durum wheat. Average ψ 0 values derived from a single point and the average x-intercept were in good agreement with ψ 0 from full curves. Osmotic adjustment in stressed leaves is easily recognized. A further test on 45 PV curves from four other durum varieties, again using the average x-intercept derived from the first set of curves, confirms the merit of the new method. It may be recommended for testing large numbers of leaves in parallel. A protocol is suggested which will permit the estimation of osmotic adjustment in previously unstudied plant material, which is for instance necessary in breeding programs. Key words: osmotic potential, pressure-volume (PV) curves, pressure chamber, osmotic adjustment, Triticum durum