Fig. 1.

Measurement of Rubisco activation status, maximal activity, and stability in vitro at 25 °C. Soluble cellular protein rapidly extracted from tobacco and each phytoplankton in CO₂-free extraction buffer (containing 5mM MgCl₂) was used to measure changes in the Rubisco ¹⁴CO₂ fixation rate after activating the extract for 0–20min in buffer containing 15mM MgCl₂ and 15mM NaHCO₃. Gray shading indicates the time when protein extract was assayed to quantify k _cat ^c, K _C, and K _O (Table 1). Data represent measures from duplicate biological samples (± SD).