A team of researchers from Cornell University has discovered how raindrops and leaf vibrations can launch plant spores into the air, where they can infect healthy plants.
The study, published in Science Advances, is the first to analyze spore dispersion at its source, using high-speed cameras and theoretical models.
The findings could help design strategies to prevent the spread of plant pathogens, which cause billions of dollars of crop losses every year.
The role of rain and wind in spore dispersion
Plant spores are microscopic reproductive units that can cause diseases in plants, such as rust, blight, and mildew.
Spores can be dispersed by various agents, such as insects, animals, and humans, but the most common and effective ones are rain and wind.
Raindrops can splash spores from the soil or from infected plant surfaces, while wind can carry spores over long distances.
However, the exact mechanism of how rain and wind interact with plant leaves to disperse spores has been poorly understood, until now.
The researchers from Cornell University conducted a series of experiments and simulations to reveal the details of this process.
The experiment: high-speed cameras and glass particles
The researchers used wheat plants infected with rust, a fungal spore that can devastate crops worldwide, as their model system.
They placed the plants in a wind tunnel and exposed them to artificial rain and wind.
They used high-speed cameras to capture the movement of the leaves and the spores during the rain and wind events.
To overcome the challenge of working with live spores, which are difficult to see and handle, the researchers used hollow glass particles that mimic the size, shape, and density of spores.
They coated the leaves with the glass particles and tracked their trajectories using the cameras.
The results: tiny tornadoes and swirling vortices
The researchers found that when raindrops hit a flexible leaf, the leaf vibrates and creates a small vortex of air around it.
This vortex can lift the spores from the leaf surface and launch them into the air. The researchers called this phenomenon a “tiny tornado”.
The researchers also found that the wind can enhance the effect of the rain by creating larger and more stable vortices around the leaves.
These vortices can carry the spores farther and higher, increasing the chances of infecting other plants.
The researchers used theoretical analysis to predict the characteristics of the vortices, such as their size, shape, and strength, and how they affect the spore dispersion.
They found that the vortices depend on several factors, such as the size and shape of the leaf, the angle and speed of the wind, and the frequency and intensity of the rain.
The implications: potential strategies to reduce spore dispersion
The study provides new insights into the physics of spore dispersion by rain and wind, which could have important implications for plant disease management.
The researchers suggest that by manipulating the factors that influence the formation and behavior of the vortices, such as the leaf stiffness, the wind direction, and the rain frequency, it might be possible to reduce the spread of spores from infected plants.
The researchers also hope that their study will inspire further research on the interaction of rain and wind with other biological systems, such as insects, seeds, and pollen.
FAQ
Plant spores are microscopic reproductive units that can produce new plants or fungi. Some spores can also cause diseases in plants, such as rust, blight, and mildew.
Plant spores can spread by various agents, such as insects, animals, and humans, but the most common and effective ones are rain and wind. Raindrops can splash spores from the soil or from infected plant surfaces, while wind can carry spores over long distances.
When raindrops hit a flexible leaf, the leaf vibrates and creates a small vortex of air around it. This vortex can lift the spores from the leaf surface and launch them into the air.
The wind can enhance the effect of the rain by creating larger and more stable vortices around the leaves. These vortices can carry the spores farther and higher, increasing the chances of infecting other plants.
The researchers used wheat plants infected with rust, a fungal spore that can devastate crops worldwide, as their model system. They placed the plants in a wind tunnel and exposed them to artificial rain and wind.
They used high-speed cameras to capture the movement of the leaves and the spores during the rain and wind events. They also used hollow glass particles that mimic the size, shape, and density of spores to overcome the challenge of working with live spores.
The study provides new insights into the physics of spore dispersion by rain and wind, which could have important implications for plant disease management.
The researchers suggest that by manipulating the factors that influence the formation and behavior of the vortices, such as the leaf stiffness, the wind direction, and the rain frequency, it might be possible to reduce the spread of spores from infected plants.
The researchers also hope that their study will inspire further research on the interaction of rain and wind with other biological systems, such as insects, seeds, and pollen.
More information: Zixuan Wu et al, Coherent spore dispersion via drop-leaf interaction, Science Advances (2024). DOI: 10.1126/sciadv.adj8092. www.science.org/doi/10.1126/sciadv.adj8092
