Biologists explain why sunflowers turn to the Sun

A long time ago, people noticed that young sunflower flowers turn to follow the sun during the day and at night return to the starting position, to meet him again in the morning in the east. But until now, scientists were unable to uncover the mystery: what makes a plant to make your daily ritual and why over time, “worship” luminary stops?

Biologists explain why sunflowers turn to the Sun
Photo – Via

In search of an answer Stacey Harmer ( Stacey Harmer ) from the University of California at Davis and her colleagues conducted a series of experiments.

In the first stage sunflowers that grew in the natural environment, the conditions have changed. One group of scientists “immobilize” to plants in general can not be rotated, and the other fixed in such a way that sunflowers at sunrise were rotated to the west. When the flowers have grown, it was found that in both groups, the leaves were 10% less than the “free” plants. This confirmed the hypothesis that the sun sunflowers supervision is necessary for more efficient growth.

Then, the scientists decided to see what caused the rhythmic “dancing” of sunflowers – internal clock or environmental conditions.

They transferred the plants that grew on the street, in a room with constant overhead lighting and found that sunflowers for several days continued to turn from side to side just like we did before.

Next, the scientists put the plant in a special room with a string of lights that are turned on, simulating the movement of the sun. When the researchers programmed the artificial lighting on tridtsat chasovoy cycle change “day” and “night”, the plants turned from side to side without regular schedules. But when light conditions become normal again, sunflowers strictly followed the artificial “sun”, showing that the internal circadian rhythms play an important role in the movement of the flower.

But most of all biologists interested in the question why after flowering sunflowers cease to rotate from side to side and freezes, “looking” in the direction of the sunrise. Then Harmer turned command of the plant to the west, and then count the number of bees and other pollinators, who sat on the flowers, addressed to the different sides of the world.

It turned out that in the morning the insects are five times more likely to have visited the flowers open to the east than rotated in the opposite direction.

“You can be sure that the bees are crazy for flowers, looking at the east, and almost do not pay attention to the plants rotated to the west”, – said Stacey Harmer.

Previous studies have shown that pollinators prefer warmer flowers, sunflowers therefore, have received a large dose of the first morning rays, are more popular.

“I always wondered how difficult to find plants – continues Harmer -. They are really masterfully adapt to environmental conditions.”

The findings , published in the edition of Science, raise more complex issues. For example, a plant determine the time and how they find the right direction when turning in the dark where the sun comes up?

But, according to experts, the fact that the sunflowers have an internal clock, and follow their own rhythms, is the “Holy Grail” in the study of complex behavior. And, as emphasized in the press release of the University, this is the first example of time synchronization of plants that live in the natural environment, which has a direct impact on the efficiency of growth.


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