Water stress and water-use efficiency in field grown wheat: a comparison of its efficiency with that of C<SUB>4</SUB> plants

Two cultivars of wheat, contrasting in their drought resistance characteristics, were grown under irrigated and non-irrigated conditions in the field for two seasons. The water-use efficiency (WUE) ranged from 0.5 to 13.8 g dry matter kg<SUP>-1</SUP> water used depending upon the growth stage, cultivar and water stress. The average WUE for the season was between 3.34 and 4.70 g dry matter kg<SUP>-1</SUP> water used. Regression analysis indicated that WUE was a function of dry matter produced and had no direct statistical relationship with the weather parameter. The WUE of plants having the C<SUB>3</SUB> system of photosynthesis, like wheat, need not be poorer than the plants with the C<SUB>4</SUB> system if comparisons are made of plants growing in their respective preferred ecological niches. Various possible reasons for the low values of WUE reported for C<SUB>3</SUB> plants are discussed