Fig. 2. Dependence of cumulative DW on cumulative WU and cumulative WU VPD^–1, for crops with high (H, irrigated) or low (L, rainfed) water availability, during the period with green area index 5 in H crops. (a) WU VPD^ß with ß = 0. (b) fit of Eq. [5] with ß = –1, VPD computed with = 0.72, fitted; line a: H crops; line b: L crops, data from Exp. PE98 were excluded (see text). See Materials and Methods for explanation of the parameter. SEE, standard error of estimations of DW (as percentage of mean dry weight in brackets).