Fig. 1.

Eleven days of net CO₂ exchange by the shoot (leaves plus stems) of a Portulaca cryptopetala plant growing in a pot. Watering was withheld on day 2 (red arrow) and recommenced on day 10 (blue arrow). During the light period of day 4, the shoot was exposed to air containing 2% O₂ (black arrow) for approx. 1 h. Shaded areas represent the 12 h dark periods. PFD incident to the top of the gas-exchange cuvette was 1000 μmol m⁻² s⁻¹. At the end of the experiment, total leaf area was 71.1 cm², and leaf and stem dry masses were 0.26 and 0.095 g, respectively.