Figure 5. Foliage abscisic acid (ABA) levels as leaf water potential (Ψl) declines during soil drought in leaves taken from girdled branches in the angiosperm species Umbellularia californica (A) and conifer species Callitris rhomboidea (B). Generalized additive model (GAM) curves and standard errors are represented by solid and dashed black lines, respectively, for the ABA data from girdled branches, and in grey from ABA data taken from intact branches. The black vertical line depicts the Ψl at peak foliage ABA level in girdled branches, and the grey vertical line the Ψl at peak foliage ABA level in intact branches.