Plot of A against
ci for control and ABA-treated plants. Data
are the combined results for three control and three ABA-treated
plants. Solid and dotted lines are nonlinear least-squares fits of
first-order exponential decay functions to data for control and
ABA-treated plants, respectively (y = 24.8 −
27.4e(−x/198),
r2 = 0.99 for control; y =
26.5 − 28.5e(−x/300),
r2 = 0.98 for ABA-treated plants). Solid
and dotted arrows point to initial operating points (circled) for
control and ABA-treated plants, respectively
(ca = 350 μmol
mol−1, vapor-pressure difference [VPD] = 1.0
kPa). Leaf temperature 25°C, photosynthetically active
radiation 800 μmol m−2
s−1.