Leaf net photosynthetic rate (A) was measured during the late
vegetative
growth stage using a portable infrared gas analyser
(IRGA)
system (PP Systems model CIRAS-1, Amesbury, MA, USA).
Measurements
were made following the protocol described by
−1
◦
Parsons et al. (1997). The relative humidity of the incoming air in to
the
IRGA chamber was maintained within 40–80%. Photosynthetically
Active Radiation (PAR) (Q), CO
2
concentration (C
) and air/leaf
temperature
in the leaf chamber (T
) were the independent variables
that were varied within specific ranges as described under
Section
2.3. Net rate of photosynthesis (A) was estimated based on
the
deficit CO
2
1
concentration in the incoming and outgoing air in
the
leaf chamber. In each experiment, measurements were made
in
1–3 leaves per plant and in six plant replicates. Measurements
taken
from three plants were used to derive the model parameters
presented in Table 1 and other three plants to represent the
observed
values in subsequent figures.