Rates of the net photosynthetic CO2 uptake the import of '“♦C-labelled assimilates in developing groundnut leaves on the 5"’, 9‘*' and I6"i positions from the stem base were followed over a 20 d maturation period. Maximum import of labelled assimilates into the leaf was observed on the 2"^ day after leaf emergence, when the developing leaf had attained 10-12 % of its fmal leaf area (% Aj). Thereafter, by the day the •‘^C-import rate declined rapidly and asymptotically to a near zero value. The rapid decline in import was offset by a rapid rise in /’n. Pjsj was first observed at 20-30 % Af. Maximum values were attained by the 6‘*’ day, irrespective of leaf area attained by the developing leaves, and were maintained up to the end of the experiment.