Internal clock helps young sunflowers follow the sun | Science News

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Internal clock helps young sunflowers follow the sun

Circadian strategy offers advantages, study finds

By
2:03pm, August 4, 2016
sunflowers

SUN SALUTATION  Mature sunflowers aim their flower heads to the east. That way, the flowers get warmer and attract more pollinators.

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Young sunflowers grow better when they track the sun’s daily motion from east to west across the sky. An internal clock helps control the behavior,  biologist Stacey Harmer and colleagues report in the Aug. 5 Science.

Depending on the time of day, certain growth genes appear to be activated to different degrees on opposing sides of young sunflowers’ stems. The east side of their stems grow faster during the day, causing the stems to gradually bend from east to west. The west side grows faster at night, reorienting the plants to prepare them for the next morning. “At dawn, they’re already facing east again,” says Harmer, of the University of California, Davis. The behavior helped sunflowers grow bigger, her team found.

Young plants continued to grow from east to west each day even when their light source didn

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