Table 3.

Relative contribution of PEPC- and Rubisco-mediated CO₂ uptake during translational phases II and IV for young fully expanded leaves of Aechmea ‘Maya’ under ambient (380 μmol mol⁻¹) and elevated (700 μmol mol⁻¹) CO₂ concentrations

	% C4 carboxylation		% C3 carboxylation
CO2 (μmol mol−1)	Phase II 0600–0900	Phase IV 1800–2200*	Phase II 0600–0900	Phase IV 1800–2200*
380	85	100	15	0
700	56	60	44	40

Percentage of C₄ carboxylation was quantified by comparison of malic acid build up and total net CO₂ uptake in each period whereby 1 mol malic acid corresponds to 1 mol CO₂. The remaining CO₂ uptake was attributed to C₃ carboxylation through Rubisco activity.

*Due to elevated CO₂ phase IV extended by starting 3 h earlier at 1500 h compared with controls.