Is it clear why sunflowers 'keep facing east' when they grow?
Sunflowers have the property that flowers move to follow the sun, so they have the name 'sunflower' in Japanese and 'Sunflower' in English, but after flowering, they basically move to the east. It will not move while facing. Botanists at the University of California, Davis have published new findings on why sunflowers have been oriented 'east' since flowering.
Flower orientation influences floral temperature, pollinator visits and plant fitness --Creux ---- New Phytologist --Wiley Online Library
Why sunflowers face east --ScienceDaily
https://www.sciencedaily.com/releases/2021/08/210811113133.htm
We Finally Know Why Older Sunflowers Keep Facing East (And Why It's a Good Thing)
https://www.sciencealert.com/we-finally-know-why-sunflowers-face-east
Researchers find out why sunflowers always face east
https://www.zmescience.com/science/researchers-find-out-why-sunflowers-always-face-east/
The nature of sunflowers that 'flowers move to follow the sun' has been known for a long time, and the scientific name 'Helianthus', which means the genus Sunflower, also means 'sunflower' in Greek. However, this property is exhibited only during the period until flowering, and after flowering, the stem becomes stiff, so basically it does not move while facing 'east'.
Professor Stacey Harmer of the Department of Biological Sciences, University of California, Davis has been working on this sunflower property for many years. In 2016, Professor Harmer announced a study that 'sunflowers use a biological clock that acts on growth hormone to follow the sun,' but this time, 'the direction is east after flowering.' Because it is advantageous for pollination to be fixed, 'the research result was announced.
Professor Harmer conducted a survey that 'artificially manipulates the orientation and temperature of sunflower flowers cultivated under outdoor control conditions,' and the orientation and temperature determine the physiological functions of the flowers and the visit status of pollinators. We investigated whether it would affect the pollination success rate.
As a result, more pollinators visit the flower when it is fixed eastward than when it is fixed westward, and the number of seeds and the weight per flower are also increased. Then it turned out.
If you look at the movie released by the research team, you can see that the sunflowers that are fixed facing east have more bees that are pollinators.
Bees visiting east- and west-facing sunflowers --YouTube
The sunflower facing west is on the left and the sunflower facing east is on the right. No bees have visited on the left side, but on the right side, around 10 bees are always in the center.
A follow-up analysis by the research team revealed that east-facing sunflowers release more pollen in the morning when pollinators are active. In response to this result, the research team conducted an experiment to 'artificially warm the sunflowers facing west', and it was confirmed that they released the same amount of pollen as the sunflowers facing east, but on the other hand, they visited the pollinator. The number of pollinators remained unchanged, with the result that 'warmed west-facing sunflowers release the same amount of pollen as when facing east, but pollinators do not approach.' The cause of this is unknown, but the research team speculates that 'the sun's ultraviolet rays may have an effect.'
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