SIMPLIFIED PROCEDURE FOR ESTIMATING TISSUE AFFINITY FOR BOUND WATER IN DURUM-WHEAT

Bound water has been studied intensively in relation to abiotic stress tolerance, but investigations of its role as a component of drought r esistance in crop plants have been hampered by lack of rapid, inexpens ive, and reliable methods capable of processing large populations in a short time. We investigated the possibility of estimating thermodynam ic properties of strongly bound water in wheat leaves (Triticum durum Desf.) using a simplified analysis of water sorption, which made use o f 39 paired isotherm curves constructed at 5 and 20 degrees C, and the rmodynamic parameters derived from them. Tissue affinity for strongly bound water (expressed as average differential enthalpy = Delta (H) ov er bar) was compared with measurements of the difference in water sorb ed (DWS) by the leaves at 5 and 20 degrees C at relative humidities of 7, 11, 33, and 43%. Measurement of DWS at 33% relative humidity gave the best estimate of Delta (H) over bar, and therefore constituted a r eliable, inexpensive, simplified method for the evaluation of tissue a ffinity for strongly bound water.