Sunflowers that face east are more productive, happier, and healthier than sunflowers that face the other direction. It's all down the warmth of the Sun.
This is the conclusion of a new study. It looked at why cheerful yellow flowers tend to mature facing east, despite the fact that they are more flexible in their youth and change their orientation to face the Sun.
Higher levels of warmth and light from rising Sun attract more bees, which leads to better growth, early pollen production and greater reproductive success.
Stacey Harmer, University of California Davis plant biologist, said that it was striking that the plants face east. They produce more offspring if they face east.
Young sunflowers (Helianthusannuus) display a unique behavior as they grow. The capitulum of the flower head moves to follow the Sun across the sky. This is shown in the video below.
Harmer and her collaborators have previously published research in 2016 that found this tracking helps in the growth of the flower and attracts pollinators.
The stem of the sunflower becomes stiffer as it matures. This significantly limits its movement. The capitulum then faces east as a result.
Researchers still don't know why sunflowers behave this way, so Nicky Creux, UC Davis biologist, created an experiment to discover.
Changes in the environment can help you understand why something is doing what it is. This is easy with east-facing sunflowers: Just turn them around. The researchers took measurements and compared the normal, east-facing controls to the turned, west facing sunflowers.
Researchers noticed that flowers facing east attracted significantly more bees in the morning. The bees did not show any preference during the rest of their day. This suggests that the morning window could make all the difference.
The east-facing sunflowers began releasing their pollen earlier than usual in the morning by approximately 30 minutes timing. This was pretty close to the time delay between peak pollinator visits times.
This is all due to the temperature of your capitulum, according to follow-up analysis. The Sun heats the flower heads, which causes them to release pollen. When heated artificially, west-facing flowers displayed similar pollen release behavior.
Although it is not clear why, artificial heating did not make a difference in pollinator visits. Researchers believe that the markings of the flowers visible to pollinators by UV light from Sun could be responsible for this phenomenon. The markings on east-facing sunflowers were more bright and were clearly visible.
It was also amazing to see the effect it had on sunflowers. The east-facing sunflowers produced heavier and more abundant seeds than the west-facing ones. The pollen from east-facing sunflowers was more successful at producing offspring.
Researchers discovered this by surrounding sunflowers with pollen-producing plants that only produced seeds. They also tested for pollen. They then used genotyping to determine if the seeds were pollinated with east or west pollen. The west-facing sunflowers had significantly more offspring.
This suggests that while facing east is not essential for a sunflower's success it can provide enough of an incentive to make it worthwhile.
The researchers stated that their results showed that mature sunflower capitulas are orientated eastwardly to manage the floret microclimate. This helps ensure the right conditions for seed development, pollination and anthesis.
The research was published in New Phytologist.
