Graphical evaluation and partitioning of turgor responses to drought in leaves of durum wheat

The relationship between relative water content (R) and turgor potential (Ψp) may be derived from pressure-volume (PV) curves and analyzed in various ways. Fifty PV curves were measured with the pressure chamber on leaves of durum wheat (Triticum durum L.). The plots of Ψp versus R were highly variable and could not be adequately described by a single mathematical function. The area below the curve was therefore determined by means of an area meter. This procedure gave the integral of turgor from full saturation to the turgor-loss point. Responses to drought treatment could thus be quantified and partitioned into effects of osmotic adjustment and elastic adjustment. These two adjustment responses, which are probably of different metabolic origin, together improve turgor maintenance in durum wheat considerably.