Fig. 2.

In situ O₂ dynamics in a leaf of I. australis, the sediment of the rhizosphere, and the water column (a), and incident light and temperature (b) over a diurnal cycle in a granite vernal pool. O₂ microelectrodes were inserted into a lacuna of a fully expanded leaf, into the sediment (10 mm depth), and at canopy height in the water column. Water column CO₂ concentrations fluctuated conversely to the intra-plant pO₂; maximum dawn CO₂ concentration was 270 μmol l⁻¹ while minimum late afternoon CO₂ concentration could be as low as 3 μmol l⁻¹ based on pH, alkalinity, and temperature (calculated according to the approach in Stumm and Morgan, 1996).