Pressure-volume curves and drought resistance in two wheat genotypes

The water relations of two durum wheat cultivars (Triticum durum Desf.) were studied throughout the growing season. Irrigated and unirrigated plants were compared from booting to milk stage; a period where water stress occurred naturally in the field. Modulus of elasticity (ε), turgid weight/dry weight ratio (TW/DW), relative water content at zero turgor (RWCo) and osmotic potential at full turgor (ε) declined throughout the season while average turgor (ψp) increased. Water stress induced a further decrease in ψπ100 and the TW/DW ratio. The elastic modulus varied greatly. During the first stages of growth, cv. Appulo (the more resistant cultivar) showed lower ε values than cv. Valforte. At the milk stage, ε was lower for the unirrigated than the irrigated plants. Correlation coefficients between the TW/DW ratio and the osmotic potential were significant for both cultivars. In cv. Valforte, TW/DW was also correlated with the average turgor and the bulk modulus of elasticity. Structural changes that affect the TW/DW ratio seem to be important factors influencing water relations and drought tolerance in durum wheat