not saturate in any of the species examined. The correlation was
closer for P. fortunei (r
2
= 0.87) than for G. robusta or A. acuminata
(r
2
= 0.74 and 0.78), and the differences between species were
significant (p < 0.01). Rectangular hyperbolae fitted to the data for
each species revealed that the estimated PPFD compensation points
(intercept with x-axis), dark respiration rates (intercept with y-axis)
and quantum efficiency (A/Q, initial slope of hyperbola) for G.
robusta, A. acuminata and P. fortunei were respectively 40.2, 47.1 and
31.6
mmol photons m
2
s
1
, 1.45, 2.18 and 0.05 mmol CO
and 0.038, 0.031 and 0.016 mmol CO
Measurements made at PPFD > 800
mmol m
2
(mmol PPFD m
2
s
1
were used to
assess the impact of leaf age and soil moisture on A and E.