Researchers Uncover Sunflowers’ Unique Dance-Like Movements in Dense Environments
Tel Aviv, Israel — Sunflowers growing in crowded environments exhibit a fascinating behavior, moving in a zigzag pattern that not only helps them capture more sunlight but also prevents them from overshadowing neighboring plants, according to new research by Tel Aviv University.
This discovery builds upon an idea first explored by Charles Darwin nearly 200 years ago. Darwin observed that plants often move in circular patterns, a phenomenon known as circumnutation. The recent study, led by Professor Yasmine Meroz of Tel Aviv’s School of Plant Sciences and Food Security and Professor Orit Peleg from the University of Colorado Boulder, sheds new light on this movement. Their findings were published in the peer-reviewed journal Physical Review X.
The Sunflower Dance
In an interview with The Times of Israel, Meroz and Peleg, who became friends during their postdoctoral studies at Harvard University, described the sunflowers’ movements as similar to dancing at a crowded party. Meroz explained, “If nobody moves, you might find yourself stuck in empty spaces or overcrowded areas. But if you dance just enough, you create space for everyone.” The researchers observed that sunflowers seem to “wiggle” in a coordinated manner, moving right and left in a zigzag pattern. This collective motion allows them to optimize their exposure to sunlight while minimizing the shadow they cast on each other.
Investigating Plant Movements
The research was inspired by earlier studies of sunflowers grown closely together in fields. These plants perceive light signals from nearby neighbors and adjust their positions accordingly. While it’s well-known that climbing plants grow in circular movements to find support, the purpose of similar movements in other plants, like sunflowers, remained unclear until now.
To explore this, Meroz and Peleg conducted a controlled experiment in a laboratory. They grew five sunflowers in close proximity and used time-lapse photography to document their movements over a week to 10 days. The resulting footage revealed the plants’ zigzagging dance, which was more pronounced than the researchers had anticipated.
“We observed that these circumnutations help the plants find an optimal configuration where each receives sufficient sunlight,” Meroz explained.
The Role of Statistical Physics
Peleg, whose research integrates physics, biology, engineering, and computer science, aimed to determine whether the sunflowers’ movements were random or synchronized. Using models from statistical physics, Peleg analyzed the patterns.
Random motion, she explained, is akin to dust particles floating aimlessly in sunlight, a phenomenon first observed by botanist Robert Brown. Despite its apparent unpredictability, physicists like Albert Einstein developed formulas to predict the average behavior of such particles.
In their experiment, Meroz and Peleg built a model to quantify the optimal movement needed for each sunflower to ensure that none were left in the shade. “We quantified this movement statistically and demonstrated through computer simulations that these random movements collectively minimize shading,” Meroz said.
The research also revealed a surprising range in the distribution of the sunflowers’ “steps,” with plants finding a “sweet spot” where their movements perfectly balanced sunlight and shade.
Plants with Memory?
Peleg noted that, like animals, plants may have a form of memory and use seemingly random movements to navigate their environment. She compared this to a dog sniffing a trail, moving its head from side to side to detect scents.
The researchers also likened the sunflowers’ collective behavior to that of birds or fish, which move in coordinated patterns. “It’s mathematically very similar,” Peleg said, adding that their study raises questions about how information is transmitted across the plant system.
Meroz hopes this research will encourage people to see plants differently. “If we lived on a plant’s timescale and could move as slowly as they do, we might walk down the street and see plants moving around us,” she said. “It would change the way we think about them.”