Figure 3.

The effect of a 4-h dark pretreatment on the incorporation of ¹⁴C into starch in intact, photosynthesizing Arabidopsis plants supplied with ¹⁴CO₂. A, Wild-type Arabidopsis plants were supplied with ¹⁴CO₂ for 30 min after 10 h of the photoperiod (white symbols) or after 6 h of the photoperiod followed by 4 h in darkness (black symbols). Samples comprising all the leaves from a single plant were harvested and frozen in liquid N₂. Starch was extracted from the leaves and fractionated by Sepharose CL2B chromatography. The ¹⁴C in each fraction was determined by scintillation counting. The results are the means and ses of four replicate samples. Label in the amylose-containing fractions is shown more clearly on an expanded y axis in the inset graph. B, Arabidopsis plants of the mutant line dpe were supplied with ¹⁴CO₂ for 30 min after 10 h of the photoperiod (white symbols) or after 6 h of the photoperiod followed by 4 h in darkness (black symbols) as described in A.