Contents

05 August 2016
Vol 353, Issue 6299

About The Cover

Cover image expansion

COVER Sunflower head just before fl oral maturation, with the Sun setting behind it. Whereas mature sunflowers always face east, young sunflower plants track the Sun from east to west during the day and then reorient overnight to face east in anticipation of dawn. Both heliotropic growth patterns are mediated by the circadian clock and enhance pollinator visits and plant yield. See pages 541 and 587.
Photo: Stephen Coleman/Alamy