You'll never guess the fascinating truth about sunflowers and why they act the way they do.
Sunflowers are a uniquely amazing life form, doing something that no other type of plant has been known to do: move in concert with the sun, gathering as much of its rays as possible over the course of an entire day. But how on Earth can it do something so, well, un-plant-like? New research may have answered this mystery once and for all.
The new paper, which was published in the journal Science, not only answers that but also why sunflowers stop doing that and only face east when they reach maturity. It has to do with circadian rhythms, the same thing that drives our own internal clock to follow a 24-hour cycle. Apparently, plants can have such an internal clock as well, according to a University of California – Davis statement.
But what about the mechanics of hte plant actually turning? That’s a result of different sides of the stem elongating depending on what time of day it is. Growth rates on the east side are highest during the day, and lowest at night, and on the west side the reverse is true.
To test this, researchers tied up the plants so they couldn’t move, and found that the flowers had less biomass than the other flowers. And when researchers tried it out with artificial light — to see if it was really based on circadian rhythms — the plants could reliably track the light’s movement at a 24-hour cycle but not at, say, a 30-hour cycle.
As for mature sunflowers, they stop turning to face west because by only facing east they attract way more pollinators — and at that stage in their lives, that’s all that matters. The reason they attract more pollinators is that east-facing flowers heat up faster, and bees like warm flowers.
“It’s the first example of a plant’s clock modulating growth in a natural environment, and having real repercussions for the plant,” said Stacey Harmer, professor of plant biology at UC Davis, in the statement. “The plant anticipates the timing and the direction of dawn, and to me that looks like a reason to have a connection between the clock and the growth pathway.”