Fig. 2.

Twenty-five days of net CO₂ exchange by the shoot (leaves and stems) of a potted Portulaca cryptopetala that was exposed to two wetting and drying cycles. Watering was withheld on days 3 and 16 (red arrows) and recommenced on days 14 and 23 (blue arrows). Shaded areas represent the 12 h dark periods. PFD incident to the top of the gas-exchange cuvette was 1350 μmol m⁻² s⁻¹. At the end of the experiment, total leaf area was 152 cm² and leaf and stem dry masses were 0.578 and 0.372 g, respectively.