Chantal Nguyen, University of Colorado Boulder

Most of us aren’t spending our days watching our houseplants grow. We see their signs of life only occasionally – a new leaf unfurled, a stem leaning toward the window.

But in the summer of 1863, Charles Darwin lay ill in bed, with nothing to do but watch his plants so closely that he could detect their small movements to and fro. The tendrils from his cucumber plants swept in circles until they encountered a stick, which they proceeded to twine around.

“I am getting very much amused by my tendrils,” he wrote.

This amusement blossomed into a decadeslong fascination with the little-noticed world of plant movements. He compiled his detailed observations and experiments in a 1880 book called “The Power of Movement in Plants.”

In one study, he traced the motion of a carnation leaf every few hours over the course of three days, revealing an irregular looping, jagged path. The swoops of cucumber tendrils and the zags of carnation leaves are examples of inherent, ubiquitous plant movements called circumnutations – from the Latin circum, meaning circle, and nutare, meaning to nod.

Circumnutations vary in size, regularity and timescale across plant species. But their exact function remains unclear.

I’m a physicist interested in understanding collective behavior in living systems. Like Darwin, I’m captivated by circumnutations, since they may underlie more complex phenomena in groups of plants.

Sunflower patterns

A 2017 study revealed a fascinating observation that got my colleagues and me wondering about the role circumnutations could play in plant growth patterns. In this study, researchers found that sunflowers grown in a dense row naturally formed a near-perfect zigzag pattern, with each plant leaning away from the row in alternating directions.

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This pattern allowed the plants to avoid shade from their neighbors and maximize their exposure to sunlight. These sunflowers flourished.

Researchers then planted some plants at the same density but constrained them so that they could grow only upright without leaning. These constrained plants produced less oil than the plants that could lean and get the maximum amount of sun.

While farmers can’t grow their sunflowers quite this close together due to the potential for disease spread, in the future they may be able to use these patterns to come up with new planting strategies.

Self-organization and randomness

This spontaneous pattern formation is a neat example of self-organization in nature. Self-organization refers to when initially disordered systems, such as a jungle of plants or a swarm of bees, achieve order without anything controlling them. Order emerges from the interactions between individual members of the system and their interactions with the environment.

Somewhat counterintuitively, noise – also called randomness – facilitates self-organization. Consider a colony of ants.

Ants secrete pheromones behind them as they crawl toward a food source. Other ants find this food source by following the pheromone trails, and they further reinforce the trail they took by secreting their own pheromones in turn. Over time, the ants converge on the best path to the food, and a single trail prevails.

But if a shorter path were to become possible, the ants would not necessarily find this path just by following the existing trail.

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If a few ants were to randomly deviate from the trail, though, they might stumble onto the shorter path and create a new trail. So this randomness injects a spontaneous change into the ants’ system that allows them to explore alternative scenarios.

Eventually, more ants would follow the new trail, and soon the shorter path would prevail. This randomness helps the ants adapt to changes in the environment, as a few ants spontaneously seek out more direct ways to their food source.

In biology, self-organized systems can be found at a range of scales, from the patterns of proteins inside cells to the socially complex colonies of honeybees that collectively build nests and forage for nectar.

Randomness in sunflower self-organization

So, could random, irregular circumnutations underpin the sunflowers’ self-organization?

My colleagues and I set out to explore this question by following the growth of young sunflowers we planted in the lab. Using cameras that imaged the plants every five minutes, we tracked the movement of the plants to see their circumnutatory paths.

We saw some loops and spirals, and lots of jagged movements. These ultimately appeared largely random, much like Darwin’s carnation. But when we placed the plants together in rows, they began to move away from one another, forming the same zigzag configurations that we’d seen in the previous study.

We analyzed the plants’ circumnutations and found that at any given time, the direction of the plant’s motion appeared completely independent of how it was moving about half an hour earlier. If you measured a plant’s motion once every 30 minutes, it would appear to be moving in a completely random way.

We also measured how much the plant’s leaves grew over the course of two weeks. By putting all of these results together, we sketched a picture of how a plant moved and grew on its own. This information allowed us to computationally model a sunflower and simulate how it behaves over the course of its growth.

A sunflower model

We modeled each plant simply as a circular crown on a stem, with the crown expanding according to the growth rate we measured experimentally. The simulated plant moved in a completely random way, taking a “step” every half hour.

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We created the model sunflowers with circumnutations of lower or higher intensity by tweaking the step sizes. At one end of the spectrum, sunflowers were much more likely to take tiny steps than big ones, leading to slow, minimal movement on average. At the other end were sunflowers that are equally as likely to take large steps as small steps, resulting in highly irregular movement. The real sunflowers we observed in our experiment were somewhere in the middle.

Plants require light to grow and have evolved the ability to detect shade and alter the direction of their growth in response.

We wanted our model sunflowers to do the same thing. So, we made it so that two plants that get too close to each other’s shade begin to lean away in opposite directions.

Finally, we wanted to see whether we could replicate the zigzag pattern we’d observed with the real sunflowers in our model.

First, we set the model sunflowers to make small circumnutations. Their shade avoidance responses pushed them away from each other, but that wasn’t enough to produce the zigzag – the model plants stayed stuck in a line. In physics, we would call this a “frustrated” system.

Then, we set the plants to make large circumnutations. The plants started moving in random patterns that often brought the plants closer together rather than farther apart. Again, no zigzag pattern like we’d seen in the field.

But when we set the model plants to make moderately large movements, similar to our experimental measurements, the plants could self-organize into a zigzag pattern that gave each sunflower optimal exposure to light.

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So, we showed that these random, irregular movements helped the plants explore their surroundings to find desirable arrangements that benefited their growth.

Plants are much more dynamic than people give them credit for. By taking the time to follow them, scientists and farmers can unlock their secrets and use plants’ movement to their advantage.

Chantal Nguyen, Postdoctoral Associate at the BioFrontiers Institute, University of Colorado Boulder

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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Jenna Guthmiller, University of Colorado Anschutz Medical Campus

The current strain of avian flu, H5N1, is responsible for the culling of millions of domestic birds and has sickened more than a dozen farmworkers in 2024, most recently in Colorado.

The Conversation U.S. asked immunologist and microbiologist Jenna Guthmiller from the University of Colorado Anschutz Medical Campus to explain the historical roots of H5N1, its mode of transmission and how to avoid coming into contact with it.

What is H5N1?

H5N1 is a subtype of influenza A viruses. Other commonly known influenza A virus subtypes include H1N1 and H3N2, which cause seasonal outbreaks in humans.

Unlike H1N1 and H3N2, H5N1 largely infects wild birds, with waterfowl such as ducks and geese being the natural reservoirs for H5N1 viruses. Most H5N1 viruses are highly pathogenic avian influenza, meaning spillovers into other bird populations can lead to high mortality rates, including domesticated poultry.

H5N1 viruses were first identified in 1959 due to an outbreak in domesticated chickens in Scotland. In 1996, waterfowl were identified as the natural reservoir for H5N1.

Since its identification, H5N1 viruses have led to four major outbreaks: in 1997, 2003-2005, 2015 and 2021-to-present. The outbreaks in 1997 and 2003-2005 led to substantial spillover to humans.

Since 2003, nearly 900 H5N1 infections in humans have been recorded. Of those infections, more than half were fatal.

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Where did H5N1 originate?

The current outbreak of H5N1 started in late 2021 and derives from the virus that caused a major outbreak in 2015.

Since 2021, H5N1 strains have spread to six continents by migratory birds. Spillover to domestic poultry has led to the culling of millions of domestic birds

Researchers have documented the current H5N1 strain in numerous mammals, with it largely affecting aquatic mammals like seals and scavenger mammals. Sporadic spillover to domestic mammals has been recorded, including to minks, goats and alpacas.

In March 2024, the U.S. Department of Agriculture reported an outbreak of H5N1 in lactating dairy cows. As of Aug. 27, 192 herds in 13 states have been confirmed H5N1 positive.

Dairy cow-associated H5N1 viruses have since jumped back into wild birds, and recent outbreaks in domestic poultry resembled H5N1 in dairy cows. Between May and July 2024, 13 confirmed H5N1 infections have occurred in humans, with all cases directly linked to dairy farms and poultry culling. https://www.youtube.com/embed/jhKI2Zskplg?wmode=transparent&start=0 The concern is that the virus could evolve to allow human-to-human transmission.

Why did the avian flu become more widespread?

It is unclear why H5N1 has become such a widespread problem. H5N1, like all influenza viruses, rapidly mutates to infect new hosts. However, H5N1 has several features that could increase its host range.

First, H5N1 viruses use a protein called hemagglutinin that allows H5N1 to infect with new hosts.

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Second, my research group identified a mutation in H5N1 viruses causing the dairy cow outbreak that allows hemagglutinin to bind to its receptor more efficiently.

Lastly, H5N1 viruses are mutating genes associated with replication and immune evasion that are known to increase the infection of mammals.

Together, these factors could heighten H5N1 transmission and increase H5N1 spillover to mammals.

How is the strain transmitted to dairy cattle?

H5N1 viruses are largely causing infections in the mammary glands of cattle rather than the respiratory tract, which is the main site of infection for other influenza viruses in mammals. Recent studies have shown that the mammary tissue has receptors for H5N1, which could make this tissue susceptible to infection.

Since the infection is largely restricted to the mammary glands, researchers believe that H5N1 is being transmitted to cows by contaminated milk equipment, particularly the milking apparatus that attaches to the cow udders. Transmission across farms is due to infected cattle movement and shared equipment and personnel across dairy farms.

To reduce transmission, in April 2024, the USDA put in testing requirements for when cows are transported across state lines. In addition, Colorado, the state with the greatest number of positive herds, requires weekly testing on farms to identify infected herds.

What are the risks to people and other animals?

H5N1 does not pose a risk to the general public, as this virus is not known to transmit between people. As all known cases were those with direct contact with infected animals, people with occupational exposure to H5N1-infected cows and poultry continue to be at the greatest risk of infection.

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People with occupational hazards should be aware of the H5N1 symptoms – similar to those of a cold – such as congestion, sore throat and fatigue, as well as conjunctivitis, more commonly known as pink eye. For more information, see the Centers for Disease Control and Prevention’s webpage on avian influenza in people.

Domestic and wild animals near dairy farms are at high risk of infection. Particularly, barn cats that have been fed raw milk have been reported dead on dairy farms with infected cows, with these animals coming back positive for H5N1.

In addition, spillover of H5N1 to other domesticated farm animals near infected dairy cows has been recorded.

What are the best ways to keep farm workers safe?

Using personal protective equipment, such as goggles and gloves, remains the best way to prevent the transmission of H5N1 to humans and from humans back to animals. People working around poultry or dairy cattle should also be aware of biosecurity measures, such as not wearing the same clothes and boots when traveling from one farm to another.

Is drinking dairy milk a concern?

As long as you are consuming pasteurized milk products, there are no concerns for infections in humans. Pasteurization is very effective at killing any H5N1 virus that ends up in milk.

People should avoid raw or unpasteurized milk, as H5N1 virus has been found at very high levels in raw milk.

Jenna Guthmiller, Assistant Professor of Immunology and Microbiology, University of Colorado Anschutz Medical Campus

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This article is republished from The Conversation under a Creative Commons license. Read the original article.

The science section of our news blog STM Daily News provides readers with captivating and up-to-date information on the latest scientific discoveries, breakthroughs, and innovations across various fields. We offer engaging and accessible content, ensuring that readers with different levels of scientific knowledge can stay informed. Whether it’s exploring advancements in medicine, astronomy, technology, or environmental sciences, our science section strives to shed light on the intriguing world of scientific exploration and its profound impact on our daily lives. From thought-provoking articles to informative interviews with experts in the field, STM Daily News Science offers a harmonious blend of factual reporting, analysis, and exploration, making it a go-to source for science enthusiasts and curious minds alike. https://stmdailynews.com/category/science/

The recent buzz surrounding the Joro spider on social media has caused a stir, with exaggerated stories painting them as a potential threat. However, according to expert entomologist Theresa Dellinger from Virginia Tech, there is no cause for alarm when it comes to these arachnids. Here are some key points that shed light on the reality of Joro spiders:

1. Origin and Spread: Joro spiders are native to east Asia and likely made their way to the U.S. through imported materials. While they have been sighted in several states, including Georgia, Tennessee, North Carolina, and South Carolina, they have not been reported in Virginia yet.
2. Similarity to Other Spider Species: Joro spiders belong to the orb weaver family, much like other spider species found in the U.S. such as garden orb weavers and golden silk orbs. While they may look intimidating due to their size, they are not aggressive towards humans.
3. Behavior and Concerns: Joro spiders are not known to pose any medical concerns, unless someone is specifically allergic to spider bites. They are shy creatures that feed on insects and play a role in controlling pest populations.
4. Environmental Impact: As a non-native species, Joro spiders may impact the ecosystem by competing with native spider species. However, the long-term effects are still being studied.
5. Precautions: Contrary to sensationalized claims, Joro spiders do not invade homes and do not require yard treatments. If they become a nuisance, they can be easily removed using a broom or insecticide spray.

Theresa Dellinger, an expert in entomology, provides valuable insights into the behavior and impact of Joro spiders, debunking myths and offering practical advice for coexisting with these creatures. As with any wildlife encounter, understanding the facts can help dispel unnecessary fear and promote a harmonious relationship with nature.

For more information, check out the Virginia Tech article.

To find additional details, take a look at the article from Virginia Tech.

https://www.newswise.com/articles/joro-spiders-are-nothing-to-worry-about-explains-expert

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