Fig. 1.

Photoperiodic flowering and post-domestication spread of crops. (A) Photoperiodic flowering of long-day and short-day plants. Long-day crops (wheat, barley, pea, lentil and sugar beet) flower under long days rather than under short days. Short-day crops (rice, maize, sorghum and wild potato) flower more efficiently under short days than under long days. (B) Post-domestication spread of crops. Long-day crops from south-west Asia and the Mediterranean, and short-day crops from south China, Africa, Mexico and the Andes are all grown at higher latitudes. Such spreading is closely associated with altered flowering times.