FIGURE 2.

Irradiance (I) response of intrinsic water-use efficiency (WUE_i) (A,B) and instantaneous water-use efficiency (WUE_inst) (C,D) for C₃ [soybean (Glycine max)] and C₄ species [grain amaranth (Amaranthus hypochondriacus)], respectively. In plots (A) and (B), solid lines were fitted using Eq. 7 and dashed lines were fitted using the non-rectangular hyperbola model (Eq. S2). In plots (C) and (D), solid lines were fitted using Eq. 10 and dashed lines were fitted using the non-rectangular hyperbola model (Eq. S3). Data are the mean ± SE (n = 4).