Glaucousness is one characteristic that has been considered a plant adaptation to drought. Two near-isogenic lines of durum wheat differing in their degree of glaucousness of the spike and the upper vegetative parts of the plant were used to determine whether genetic variation in glaucousness traits reflects differences among durum wheat genotypes in cuticular conductance, leaf water status, photosynthesis and WUE. The importance of WUE in Mediterranean environment is discussed with particular concern to the key role of wax bloom (glaucousness) in drought tolerance.