AbstractLycopenc biosynthesis of parenchyma chromoplasts was studied in detached tomato fruits,Lycopersicum esculentumMill, cv. Waltham Forcing, and found to be phytochrome mediated. A few minutes of red light during the day enhanced lycopene formation. Far‐red irradiation did not enhance lyco‐pene biosynthesis. Far‐red following red nullified the promotive effect of red light. Lycopene content increased two‐fold in the presence of abscisic acid. Ripening of tomatoes was inhibited when gibberellin, kinetin and ascorbic acid were applied to green tomatoes. Gibberellin (A3) was more inhibitory to lycopene synthesis than