https://phys.org/news/2023-10-sunflowers-sun-mechanism.html
Sunflowers famously turn their faces to follow the sun as it crosses the sky. But how do sunflowers "see" the sun to follow it? New work from plant biologists at the University of California, Davis, published Oct. 31 in PLOS Biology, shows that they use a different, novel mechanism from that previously thought.
"This was a total surprise for us," said Stacey Harmer, professor of plant biology at UC Davis and senior author on the paper.
Most plants show phototropism—the ability to grow toward a light source. Plant scientists had assumed that sunflowers' heliotropism, the ability to follow the sun, would be based on the same basic mechanism, which is governed by molecule called phototropin and responds to light at the blue end of the spectrum.
Sunflowers swing their heads by growing a little more on the east side of the stem—pushing the head west—during the day and a little more on the west side at night, so the head swings back toward the east. Harmer's lab at the UC Davis College of Biological Sciences has previously shown how sunflowers use their internal circadian clock to anticipate the sunrise, and to coordinate the opening of florets with the appearance of pollinating insects in the morning.
(Score: 3, Informative) by jelizondo on Wednesday November 08 2023, @12:23AM
As they say, don’t read the fine article.
So they don’t know how but real soon now they will find out. Or not. Who knows.
Nothing to see, move on.
(Score: 2, Interesting) by Runaway1956 on Wednesday November 08 2023, @01:36AM
So the sunflower grows more on the sunward side of the plant. Sounds reasonable, doesn't it? But - when the sunflower has already grown to it's maximum height, don't the flowers continue to track the sun? If memory serves correctly, those flowers track the sun, until just about the time the flower petals start turning brown. At which time the flower points east, until it is cut down, or blown down, or whatever.
Rapid growth on the sunward side may or may not take place. Such growth may or may not contribute to the movement of the flower. But, I'm pretty darned sure that other things are happening here.
Too bad this story didn't come out at the beginning of the season. I'd be out there taking measurements to see if there was anything at all to this hypothesis.
“I have become friends with many school shooters” - Tampon Tim Walz
(Score: 2, Insightful) by Anonymous Coward on Wednesday November 08 2023, @02:06AM
They don't describe the novel mechanism.
At least not what I'd call "describe". More like they found that in some cases (outdoors) it does not use a known mechanism (which it uses for indoors).
(Score: 2) by ledow on Thursday November 09 2023, @09:44AM
Fun fact - the Latin/Italian name for a sunflower is a girasole - basically "sun-turner".
This potentially useless fact was brought to you courtesy of a pedant.