Scientists have explained the mechanism and purpose of sunflower turns behind the sun. Why does a sunflower turn to follow the sun? Does the sunflower follow the sun

A series of experiments showed that the movement of a sunflower corresponds to a 24-hour circadian rhythm. Scientists tried to “deceive” the plants by artificially changing the duration of the movement of the light source up to 30 hours. However, in this case, sunflowers moved unevenly, which affected their growth, biomass gain and yield.

It is known that sunflower inflorescences turn after the sun during the day, and at night they change their position again in order to “look” to the east at dawn. After the sunflowers fade, they stop turning towards the sun.

Scientists explain that the movement of the sunflower inflorescence occurs due to the uneven growth of the plant. One side of the stem grows faster than the other, causing the inflorescence to turn.

In another experiment, scientists artificially limited the movement of plants. They tied some of the buds so they couldn't rotate, or turned the pots around so the plants wouldn't face the sun in the morning. It turned out that the leaves of both groups of sunflowers were 10% smaller than those of plants that followed the sun.

In addition to accumulating more biomass, sunflowers have gained another advantage: plants facing the sun are much more attractive to insects. Five times as many bees flew up to the flowers facing the east in the morning.

“Bees go crazy for east-facing plants while ignoring west-facing flowers,” says Stacey Harmer of the University of California, Davis. “On the sunny side, plants warm up faster, and warm flowers attract more pollinators.”

Anna Khoteeva

Fibonacci sequence discovered in sunflower flower

According to biologists, large flowers are one of the most obvious and beautiful demonstrations of the Fibonacci sequence. This numerical sequence is a series of natural numbers, where each subsequent number is equal to the sum of the two previous ones. The sequence might look like this: 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144…

The researchers found that the seeds are arranged in two rows of spirals, one of which goes clockwise, the other counter-clockwise. According to scientists, in most sunflower inflorescences, you can find a combination of numbers included in the Fibonacci sequence - for example, 34 and 55 or 55 and 89. And if you have a very large sunflower in front of you, then you can count 89 and 144 seeds.

In 2012, the Museum of Science and Industry in Manchester (UK), in honor of the centenary of the birth of the mathematician, launched an unusual project - Turing Sunflowers, inviting everyone to grow a sunflower and bring a flower to the museum (or send a photo of the plant).

This project resulted in the collection of 657 photographs, which took almost four years to process and analyze. Since seeds are usually clearly visible in the inflorescence of a sunflower, scientists were able to count their number and confirm that the Fibonacci pattern is indeed traced in the flowers.

Biologists still cannot understand the mechanism with which the “commitment” of certain plants to numerical sequences is associated. The problem is that plants don't always show this pattern. In the case of the studied sunflower flowers, seed patterns corresponding to the Fibonacci sequence were found in approximately 80% of the plants. The remaining inflorescences showed more complex patterns.

Anna Khoteeva

Reference

British mathematician Alan Turing was interested in such regularities in the first half of the last century. The scientist became famous for developing a method during World War II that helped break the code of the German Enigma cipher machine. In addition, Turing had a significant impact on the development of computer science and artificial intelligence. After the war, the scientist became interested in mathematical patterns in plants.

To begin with, it is worth clarifying one very important thing. The statement that sunflowers always follow the Sun is true only if we are talking about young, not yet opened sunflower flowers. Contrary to popular belief, mature sunflower flowers do not follow the Sun and are usually eastward.
Unopened sunflower buds really follow the Sun, changing their position during the day. This phenomenon is called heliotropism (see paragraph at the end of the article).

Sunwatching is essential for sunflowers to grow more efficiently. Scientists fixed the plants, preventing them from turning, or, conversely, rotated the pots, disrupting the natural course of movement. In both cases, the leaves of the plants turned out to be about 10% smaller than those of the neighbors, who calmly turned after the Sun.

In addition, experts put several dots on the stem with a marker to study how the sunflower moves behind the Sun. The scientists monitored the dots with a video camera. If the distance between them changed, this meant that the flower stem grew where these points were drawn.
When the plants turned to follow the Sun during the day, the eastern side of the stem grew faster than the western side, causing the flower itself to turn towards the Sun. And at night, the western side grew faster, and the stem turned the other way.

The secret of sunflower movement lies in the uneven growth of its stem. According to scientists, direct sunlight kills the growth hormones contained in the stem, which are called auxins. The uneven distribution of these hormones throughout the stem causes the sunflower to grow slower on the sunny side and faster on the shady side, thus tilting the entire stem towards the sun. With a change in the position of the sun, the distribution of auxins along the stem also changes, which in turn leads to a change in the slope of the flower.

Thus, the movement of the plant is carried out with the help of special motor cells involved in the growth mechanism and located in the flexible base of the flower. It turned out that this movement depended on the internal clock of the plant - circadian rhythms that control various life processes associated with the onset of day, night, morning and evening. The "clock" controls the rate of growth and causes one side of the stem to grow faster than the other. Due to this, the sunflower gradually turns after the Sun.

As the sunflower matures and the flower opens, the overall growth slows down and the plants stop moving during the day, remaining oriented to the east. The fact is that the plant reacts more strongly to sunlight in the early morning than in the afternoon, so it gradually stops moving to the west during the day.

How do sunflowers move at night?
As we all know, unopened sunflower buds meet the sun in the east in the morning and see it off in the west in the evening. Here it would be possible to finish our article, if not for one "but": in the morning, sunflower buds are again directed to the east! A logical question arises: “how?” Why does the sunflower keep moving at night, without any influence from the sun? Moreover, at night, sunflower movements occur at a much higher speed than during the day.
To our dismay, scientists cannot yet answer this question with certainty. According to one theory, at night the cells of a sunflower release the energy that has accumulated when the stem is tilted, "springing" the flower back. According to another theory, the night movement of the stem does not depend on the sun and is due to the “internal clock” of the sunflower itself.
Why does an adult sunflower always face east?
With the growth of the stem and the weight of the flower, the redistribution of growth hormones has a less and less noticeable effect. Eventually, the sunflower flower becomes too heavy to move. Therefore, after ripening, the sunflower no longer follows the Sun and always points to the east. But why east?
Researchers also do not have an exact answer to this question. Some scholars argue that one night the flower "springs" to the east and is no longer able to repeat its journey to the west.
Be that as it may, scientists continue to study the sunflower, which, unexpectedly for many, turned out to be something much more complex than just a flower that constantly follows the Sun.

Heliotropism of flowers
Heliotrope flowers track the movement of the Sun across the sky during the day, from east to west. At night, flowers can orient themselves rather haphazardly, but at dawn they turn to the east, towards the rising star. Movement is carried out with the help of special motor cells located in the flexible base of the flower. These cells are ion pumps that deliver potassium ions to nearby tissues, which changes their turgor. The segment bends due to elongation of the motor cells located on the shadow side (due to the increase in hydrostatic internal pressure). Heliotropism is the plant's response to blue light. One of the most heliotropic flowers is the sunflower, which follows the sun most of the other flowers, especially at an early age, until its head grows to a large size and becomes too heavy to move (at which time all its forces are concentrated on the ripening of seeds ). To a greater or lesser extent, almost all flowers are heliotropic.
Some sun-following plants are not pure heliotropes: their circadian movements are initiated by sunlight, and often continue for some time after it has disappeared.
There is a widespread misconception that sunflowers "stretch" towards the sun (heliotropism). In fact, mature sunflower flowers usually point east and do not move. However, sunflower buds (before flowering) have heliotropism. They change their orientation from east to west during the day.

MOSCOW, August 5 - RIA Novosti. Sunflowers have an amazing ability to constantly "look" at the Sun thanks to a mutation that changed the work of their "internal clock" in such a way that they orchestrate the growth of its cells in a very unusual way, causing the inflorescence to rotate from east to west during daylight hours, according to an article published in journal Science.

"The fact that the plant has an idea of when and where the Sun will rise from led me to assume that there is a connection between the "bioclock" and the chain of proteins and genes that control the growth of sunflowers. In addition to the fact that this way the flower receives more light, it even more attracted to bees, as they love warm surfaces,” said Stacey Harmer (Stacey Harmer) from the University of California at Davis (USA).

Based on this assumption, Harmer and her colleagues uncovered one of the oldest and most interesting mysteries of botany, studying the work of the so-called circadian rhythms that control all processes inside the cells of plants and animals depending on the time of day, and their influence on the work of oxin, a stimulant protein. growth.

To do this, the authors of the article grew several sunflowers, some of which were planted in the laboratory, where the light was constantly on, while others were planted in an ordinary field. Scientists fixed some of the plants in tubs in such a way that they could not turn behind the Sun, which allowed them to assess the consequences of abandoning such an evolutionary adaptation.

Van Gogh's sunflowers have gene mutations, scientists have foundSunflowers depicted in a series of Van Gogh paintings show signs of gene mutations, according to an article published by scientists from the University of Georgia (USA) in the journal PLoS Genetics.

In revealing the principles of this movement, they were helped by a witty trick invented by one of the authors of the article - biologists took a marker and put several dots on the stem of a sunflower, which they followed with a video camera. If the distance between them changed, this meant that the flower stem grew where these points were drawn.

As observations have shown, the “motor” in the movement of the flower was the internal clock of the plant - a set of light-sensitive proteins and genes “connected” to them that control various life processes associated with the onset of day, night, morning and evening.

If the duration of the day changed artificially, then the sunflowers lost the ability to orient themselves to the Sun, even if the artificial light source moved across the “sky” in the same way as the real star. This immediately negatively affected the flower growth rate, biomass recruitment and seed development.

The antennae of cucumbers wrap around the whip thanks to the "spring" cells.Cucumber tendrils have gained the ability to wrap themselves around and attach to tree branches and lashes in a greenhouse thanks to "spring" cells in special fibers that coil the antennae into a spiral when these cells "dry" and then shrink, biologists say in an article published in the journal Science.

The felt-tip "dots" told how exactly this happens - it turned out that these clocks affect the movement of the flower in two ways: by controlling the growth rate and causing one side of the stem to grow faster than the other. Due to this, the sunflower gradually turns during daylight hours, following the Sun.

Such a sunflower trait may have one surprising evolutionary advantage - as Harmer and her colleagues found, bees like warm flowers, especially in the morning, and turning towards the Sun helps the flower warm up faster and attract more pollinators.

A long time ago, people noticed that young sunflower flowers during the day turn after the sun, and at night they return to their original position in order to meet him again in the east in the morning. But until now, scientists could not solve this mystery: what makes plants perform their daily ritual and why does the "worship" of the luminary stop over time?

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

At the first stage, conditions were changed for sunflowers growing in their natural environment. Scientists “immobilized” one group so that the plants could not turn at all, and the other was fixed in such a way that sunflowers turned west at sunrise. When the flowers grew up, it turned out that the leaves in both groups were 10% smaller than in the "free" plants. This confirmed the hunch that sun exposure is necessary for sunflowers to grow more efficiently.

Then the scientists decided to check what caused the rhythmic "dances" of sunflowers - the internal clock or environmental conditions.

They moved plants growing outdoors into a room with constant overhead lighting and found that the sunflowers continued to turn from side to side for several days, just as they did before.

The scientists then placed the plants in a special room with a string of lamps that turned on in turn, simulating the movement of the sun. When the researchers programmed the artificial lighting to a thirty-hour "day" and "night" cycle, the plants turned from side to side without a regular schedule. But when the light regime returned to normal, the sunflowers strictly followed the artificial "sun", showing that internal circadian rhythms play an important role in the movement of the flower.

But most of all, biologists were interested in the question of why, after flowering, sunflowers stop turning from side to side and freeze, "looking" towards the sunrise. Then the Harmer team turned part of the plants to the west, and then counted the number of bees and other pollinators that landed on flowers facing different parts of the world.

It turned out that in the morning hours, insects visited flowers facing east five times more often than those turned in the opposite direction.

"You can see that the bees just go crazy for east-facing flowers and hardly pay attention to west-facing plants," notes Stacey Harmer.

Previous research has shown that pollinators prefer warmer flowers, so sunflowers that receive a higher dose of early morning rays are more popular.

"I've always been amazed at how complex plants are," continues Harmer. "They're really adept at adapting to their environment."

The results of the study, published in Science, raise more complex questions. For example, how do plants tell time and how do they find the right direction when they turn in the dark to where the sun will rise?

But according to experts, the very fact that sunflowers have an internal clock and are guided by their own rhythms is the "Holy Grail" in studying their complex behavior. And, as emphasized in a press release from the university, this is the first example of time synchronization in plants living in the natural environment, which has a direct impact on growth efficiency.