For those of us in the northern hemisphere right now, the days are short, and the nights are long. We're yearning for more sunlight. Sunlight is right around the corner. Until then, think of sunflowers!
Have you ever noticed that sunflowers follow the sun? This motion of following the sun throughout the day is heliotropism. Heliotropism is a form of phototropism, where an organism responds to light (either towards the light, or away from the light).
In the mornings, sunflower heads face towards the sun in the east, and follow it throughout the day, where they finally end in the west. They then reposition themselves to face the sun again by morning. Once the young flowers reach maturity, they remain east-facing towards the sun.
The mechanisms of how they do it, are due to circadian rhythms, or their internal clocks, which tells the plant what to do during a 24-hour cycle. In this case, it signals the growth rate of the plant's stem: during the day, the side facing east grows (and moves the sunflower head towards the west), while at night the side facing west grows (and moves the sunflower head towards the east). At maturity, the sunflower head remain facing the sun in the east, which warms up the flower, thereby helping them attract pollinators.
Have you ever noticed that sunflowers follow the sun? This motion of following the sun throughout the day is heliotropism. Heliotropism is a form of phototropism, where an organism responds to light (either towards the light, or away from the light).
In the mornings, sunflower heads face towards the sun in the east, and follow it throughout the day, where they finally end in the west. They then reposition themselves to face the sun again by morning. Once the young flowers reach maturity, they remain east-facing towards the sun.
The mechanisms of how they do it, are due to circadian rhythms, or their internal clocks, which tells the plant what to do during a 24-hour cycle. In this case, it signals the growth rate of the plant's stem: during the day, the side facing east grows (and moves the sunflower head towards the west), while at night the side facing west grows (and moves the sunflower head towards the east). At maturity, the sunflower head remain facing the sun in the east, which warms up the flower, thereby helping them attract pollinators.
Have a look at this research article published in Science, or watch this video produced by Science that explains it.
