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Internal clock choreographs sunflowers’ moves

Sunflowers bend when one side of the stem grows faster than the other.

Sunflowers bending to track the path of the sun from east to west, straining to make the most of each day is a common sight during the summer. And so is the plant’s move towards the east at night in preparation for daybreak.

But contrary to common perception, these flowers respond not simply to light, but also to an internal clock, according to a new study.

Sunflowers bend when one side of the stem grows faster than the other, the study added.

For the study, plant biologists Hagop Atamian and Stacey Harmer of the University of California at Davis in the US grew sunflowers in a field and then transferred them to growth chambers with a fixed overhead light that was always on.

The plants continued their daily journey from east to west and back for several days after the transfer, suggesting that they were not responding only to the direction of the light, but their own timekeeper, Nature reported.

The researchers presented the findings this week at the annual meeting of the American Society of Plant Biologists in Portland, US.