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Fig. 1. WUE vs. VPD showing fit of Eq. [4], for crops with high (H, irrigated) or low (L, rainfed) water availability, during the period with green area index 
5 in H crops. (a) VPD computed with 
= 0.50; line a: 
H fitted with ßH = –1; line b: H and ßH both fitted. (b) VPD computed with = 0.72 (adjusted for H crops); line a: H fitted with ßH = –1; line b: L fitted with ßL = –1, data from Exp. PE98 was excluded (see text). See Materials and Methods for explanation of the parameter, and Table 5 and Table 6 for fitting details.
