PerspectivePlant Science

How do sunflowers follow the Sun—and to what end?

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Science  05 Aug 2016:
Vol. 353, Issue 6299, pp. 541-542
DOI: 10.1126/science.aah4439

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  1. Stem orientation

    Phototropically driven auxin movement promotes growth of the shaded side over the illuminated side of the stem, causing curvature that keeps the shoot tracking the Sun westward. As the Sun passes the zenith, the shaded side becomes the east side, continuing to drive curvature westward. At night, intrinsic circadian signals cause auxin to reaccumulate on the west side, driving the direction of shoot growth back east.

    GRAPHIC: V. ALTOUNIAN/SCIENCE