Young sunflowers do what looks like a slow dance each day, turning and swaying of their own apparent volition, and now new research finds that these moves are driven by the sun, plant hormones and the sunflowers' internal clock.
This behavior of sunflowers was noticed way back in 1898, but the new study -- published in the journal Science -- is the first to explain in detail why it happens. The study is also the first to show that internal clock regulation of growth promotes overall plant yield, which in this case can lead to hefty, leafy tall sunflowers.
The findings add to growing evidence that plants are more animal-like than most of us might think.
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"Plants are exquisitely sensitive to the environment -- that is how they survive while stuck in one place -- and have senses very analogous to all the human senses," senior author Stacey Harmer, a professor in the University of California at Davis' Department of Plant Biology, told Discovery News. "For me, the big difference is the time scale of many of the responses."
"Plants actually have color vision," she continued. "They have several families of photoreceptors that allow them to see many different wavelengths of light: UV, blue, green, red, far-red ... . Note that plants can see wavelengths of light that humans can't detect (UV and far-red). They use these photoreceptors, in particular, those that are sensitive to blue light, to track the sun."
Growing sunflowers "watch" the sun and move with it, beginning their days with their heads facing east, swinging west throughout the day, and turning back to the east at night.
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