Flowers like sunlight. With it, they are able to carry out photosynthesis, and it’s a necessary part of many plants’ growing and living process. But new research also shows that sunlight may be important for a number of other things in a plant’s life as well.
Many kinds of flowers actually try their best to face the sunlight to get more of it; among those are sunflowers. As they start their day, they face the East to anticipate the sunrise, and then they track the Sun from East to West through the sky until the Sun inevitably sets. Throughout the night, the sunflower resets its position to face the Sun to the East again in the morning.
Such behavior is best observed in younger flowers, as they tend to lose the determination to face the right way as they mature. In a study published in Science, researchers found that this behavior plays a huge role in pollination candidacy, as well as growth.
They do this with a Circadian clock, which may sound familiar because animals (people included) also have a Circadian clock, which helps them know when it’s time to wake up and fall asleep.
The internal Circadian clock helps them face the East for the Sun in the morning, but it also plays a big role in helping the plant to grow as large as it can, as well as reproduce.
By facing the East, a flower warms up much more quickly as the Sun rises than a flower that faces the opposite direction does. This heat is a direct magnet for pollinators, which means flowers that have more effective Circadian clocks tend to get pollinated more frequently.
Showing that the warmth of Sunlight has an effect on pollination was easily demonstrated by using a portable heater to warm up flowers that weren’t facing the Sun, and pollinators, sure enough, went after the artificially-heated flowers rather than the colder ones.
It’s worth also noting that during the study, scientists were unable to trick the sunflowers’ sense for Sunlight. Even when trying to trick the plants with artificial light, they were unable to make the Sunflowers face the artificial light, which means their ability to face East to anticipate the Sun is based off of an internal clock and not light detection.
Also observed during the study is plants that were unable to face the East in the mornings grew less (by up to 10%). They figured this by essentially forcing some sunflowers to face the West by tethering them to a stake and then rotating them to the West.
It would seem that this internal Circadian clock is essential to more than one aspect of a Sunflower’s life cycle, and likely other kinds of plants as well.
Source: University of California - Davis