Typically, plants grow in crowded environments where neighboring plants compete for light while shading each other. The presence of neighboring plants varies through space and time, and plants have developed the ability to detect neighboring plants and grow away from their shade. Although it is generally accepted that these responses help plants increase their individual light exposure, it is not clear how plants find solutions that are beneficial for them as a whole. In a new study, physicists from Tel Aviv University and elsewhere focus on the spontaneous self-organized pattern formation of sunflower flocks mediated by shade avoidance. Their analysis reveals that circumnavigation (the innate movement of plants) results in random perturbations that follow a restricted random walk.
Circling is widespread in plant systems and is commonly associated with exploratory behavior, but its role is difficult to quantitatively understand. otherswere the first to report their role in promoting optimal growth patterns in dense plant populations that shade each other. Image courtesy of Manuel H.
“Previous studies have shown that when sunflowers are planted close together in a field and shade each other, they will grow in a zigzag pattern, one forward and one backward, to avoid shading each other,” said Professor Yasmin Meros of Tel Aviv University.
“That way the plants can grow side by side, maximizing the light they receive from the sun and maximizing photosynthesis overall.”
“In fact, plants know how to distinguish between the shadow of a building and the green shadow of their leaves.”
“When they sense the shadow of a building, they usually don't change their growth direction because they know it won't have any effect.”
“But when a plant senses shadow, it grows away from the shadow.”
In this study, the researchers investigated the question of how sunflowers “know” how to grow optimally (i.e. to capture the most sunlight collectively) and analysed the growth dynamics of sunflowers in the lab that exhibit a zigzag pattern.
Meros and his colleagues grew sunflowers in high-density environments, photographing them every few minutes as they grew, and then stitched together the images to create a time-lapse video.
The researchers followed the movements of each sunflower and observed the blossoms dancing en masse.
According to the authors, Darwin was the first to recognise that all plants grow by exhibiting a kind of cyclical movement (circumlocution), and that both stems and roots exhibit this behaviour.
But until now, apart from a few examples such as vines that grow in large circular motions searching for something to grab hold of, it hasn't been clear whether this is an artefact or an important feature of growth. Why would a plant expend energy growing in a random direction?
“As part of our research, we carried out a physical analysis to capture the behaviour of each sunflower in the colony and found that they dance to find the optimal angle to avoid blocking the sunlight of their neighbours,” Professor Meros said.
“We statistically quantified this movement and showed through computer simulations that these random movements are used collectively to minimize the amount of shadowing.”
“We were also very surprised to see that the distribution of sunflower stride lengths was so wide, spanning three orders of magnitude, from nearly zero displacement to moving two centimetres in either direction every few minutes.”
“Sunflower plants take advantage of the fact that they can use both small, slow steps and large, fast steps to find the optimal arrangement for their population,” Professor Meros said.
“That means that if the steps are narrow or wide, the arrangement will increase mutual shading and reduce photosynthesis.”
“It's like a crowded dance party, where people dance around to get more space. If you move too much, you get in the way of the other dancers, but if you move too little, it doesn't solve the crowding problem, because one corner of the square will be very crowded and the other side will be empty.”
“Sunflowers also exhibit similar communication dynamics: a combination of response to the shade of neighboring plants and random movement without regard to external stimuli.”
of result Published in the journal Physical Review X.
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Chantal Nguyen others2024. Noisy turning movements promote self-organized shade avoidance in sunflowers. Physical Review X 14 (3): 031027; doi: 10.1103/PhysRevX.14.031027
Source: www.sci.news
