Fig. 1. The increase in dry mass over three 24‐h periods for soybean leaves exposed to various [CO₂] during the dark periods, but 350 µmol mol^–1 [CO₂] during the light periods. Values for second, third and fourth trifoliolate leaves are expressed relative to values of the same leaves exposed to 370 µmol mol^–1 [CO₂] during the dark. Vertical bars indicate s.e.