Fig. 5.

Shows the results of pulse–chase experiments where spinach leaves were confined in ¹⁴CO₂ for 20 s (the pulse) and were then exposed to non-radioactive air (the chase). See methods. The figure shows the time-course of the partition of ¹⁴C isotope into various fractional groups of compounds in spinach leaves following their exposure to the ‘chase’ with unlabelled CO₂ for 240 s and illuminated to the equivalent of 50% direct sunlight. It is of note that starch and cationic compounds retained and continued to show increasing ¹⁴C radioactivity while the radioactivity in the total soluble fraction and the pool of anionic compounds declined. The time-course of changes in ¹⁴C radioactivity are shown for starch, •; neutral and anionic compounds, ■; the cationic fraction, □ and total soluble radioactivity, Δ