Why Sunflower Always Face Sun?

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Sunflower which got its name from sun, always faces the sun. But why? Why do sunflowers move their blooms to always face the sun over the course of a day? First, it is partially true. Once sunflowers reach maturity, they stop tracking the sun and only faces east. Let’s look, what science says:

Science of Sunflower

Researchers says the young plant’s sun-tracking (also called heliotropism) can be explained by circadian rhythms. Circadian rhythms are the behavioral changes tied to an internal clock that humans also have, which follow roughly a 24 hour cycle. A young flower faces east at dawn and greets the sun, then slowly turns west as the sun moves across the sky. During the night, it slowly turns back east to begin the cycle again.

They explain, the plant’s turning is actually result of different sides of the stem elongating at different times of day. Higher growth rate on the east versus west side of the stem during the day enables the shoot apex to move gradually from east to west. At night, the higher growth rate on the west side culminates in the apex facing east at dawn. For study, researchers tied plants up so they couldn’t move or turned them away from the sun. They found It resulted in “decreased biomass and less leave area” than flowers that could move with the sun.

Mature sunflowers respond differently to the sun. As growth slows down, the circadian clock ensures that the plant reacts more strongly to light early in the morning than in the afternoon. So it gradually stops moving westward during the day.

The researchers compared mature flowers facing east with those they turned to face west, and found that the east-facing blooms attracted five times as many helpful pollinators. That’s because the east-facing flowers heat up faster and, bees like warm flowers.