What is heliotropism?
If you haven’t noticed, a young sunflower will always face the sun. This sun tracking is called heliotropism. Heliotropism is a plant’s response to sunlight which corresponds to the directional growth of the plant. Sunflowers are thought to participate in heliotropism due to an internal clock, similar to humans. The biological clock helps the plant grow to its fullest and receive the most energy possible.
What is the complete cycle of heliotropism?
The movement of the sunflowers is often referred to as heliotropism. The sunflower head will be facing east at dawn, ready for the sun to rise. The sun rises as the sunflower’s head begins to rise with it. As the sun moves across the sky throughout the day, the sunflower head tracks it. Eventually, when the sun sets in the west, the head finishes in this position. Overnight it gradually returns to face east, ready to greet the sun.
How do sunflowers move?
When a young sunflower plant is growing, it tracks the sun for ultimate growth, and the stem plays a vital role in this. The stem elongates during the day to support the moving head. In the morning, the east side of the stem will expand as the day goes on, allowing the head to move west. And then, at night, the reverse happens, and the west side of the stem will elongate to allow the head to move back east.
Why do young sunflowers always face the sun?
Young sunflowers need to track the sun to get the optimum energy to grow strong. This is known as photosynthesis, which is the act of leaves collecting the sun’s rays and converting these into energy and food for the plant. A lack of sun will leave a plant weak. Tests have been carried out over the years, experimenting with sunflowers, and one experiment attached the sunflower stem in one position so it couldn’t move. As a result, the sunflower had less leaf area and decreased biomass.
Another reason for sunflowers giving up their heliotropic ways is for the bees! Bees are five times more likely to land on a flower facing eastwards than one facing west. This is because the flower will become warmer quicker from the morning sunlight. Bees prefer warmer blossoms so that they will be attracted to these flowers.
What are the benefits of facing east?
As the sunflower matures, it must ensure its legacy will live on. As mentioned above, it faces east to encourage bees to help it pollinate. The sunlight and warmth encourage the flowers to bloom and produce pollen quicker than they were facing west. Many experiments have been carried out to test this theory through genotyping. Sunflowers also grow larger and heavier seeds if facing east.
Sunflowers have fascinated humans for many years and continue to draw our attention with their human-like movements in correlation to the sun. These bright flowers have a circadian rhythm, similar to humans’ biological clock, and once they reach a mature age, they remain facing east to help the bees pollinate. Sunflowers are so recognizable, their majestic yellow petals provide colour to a landscape and beauty to the eye."
Sunflowers are rich in healthy fats, beneficial plant compounds, and several vitamins and minerals that may play a role in reducing your risk of common health problems, including heart disease and type 2 diabetes. Sunflower seeds are popular in trail mix, multi-grain bread, nutrition bars, and for snacking straight from the bag. You can read more about sunflower seeds, including their nutrition, benefits, and how to eat them here
All the best Jan