Come and see them “give birth” again in the spring breeze, and “give birth” to their babies!

Spring is here, and it’s the season when everything comes back to life... no, it’s the season when willow catkins fly wildly!

The catkins flying in the air not only affect the vision, but also make people sneeze and even cause skin allergies.

But what's wrong with the catkins? They just want to use the spring breeze to sow seeds.

Copyright image, no permission to reprint

Compared to animals, plants seem to be more ruthless towards their children (seeds), always sending them far away (after all, if they stay with them, they will have to compete with them for sunlight, land and water in the future).

As a result, plants have evolved a variety of unique methods of seed dispersal.

Since their own power is limited, most of them choose to rely on external forces. Some plants tend to use the wind in nature to spread their seeds, just like the catkins we mentioned at the beginning.

Today, I will share with you some information about those plants that are good at taking advantage of the east wind, and see what humans have learned from these plants.

01

Dandelion's Promise

Although they look similar to catkins, dandelions do not seem to be hated by people. Instead, they carry a lot of romance.

With the help of a breeze, dandelions can easily fly hundreds of meters away.

Although the reason for this is related to its light body, more importantly, it is the "buoyancy" created by the fluff.

Observing with the naked eye, we can see that there are hundreds of extremely fine pappus on dandelion seeds. In fact, the structure of each pappus is extremely complex. Under a microscope, the tip of the pappus is forked to form many sharp thorns that are difficult to see with the naked eye.

This unique fluff gives the dandelion a unique way to fly, as the airflow generated by the movement of the pappus itself interacts with the airflow around the seeds during its descent.

A pair of small vortices (vortex rings) form on its "head", providing additional air resistance to the dandelion seed below, allowing it to stay in the air longer.

Dandelion seeds and the vortex rings generated by the flow around them. Source: Reference [1]

Experimental test data show that compared with human parachutes of the same mass and wind-exposed area, dandelions stay in the air about four times longer.

Scientists are very interested in this strange phenomenon and are conducting bionics research on dandelions in an attempt to develop new aircraft and save fuel consumption of current airplanes and other aircraft.

At the same time, dandelions can also provide reference for the design of parachutes. Scientists hope to invent new types of parachutes to rescue more people.

02

Waltz of Maple Seeds

Unlike the "paratrooper" dandelions, the seeds of some plants are more eager to fly. They even want to directly grow wings and take off on the spot.

Nature has given birth to countless magical plants, some of which have evolved propeller-shaped seeds (①②③④ in the figure below) or flapping/disc-shaped seeds (⑤⑥⑦ in the figure below).

Among them, maple seeds are the most distinctive.

Various forms of "flying seeds". Source: Reference [2]

The seeds of the maple tree have a nice name - samaras. As the name suggests, they have blades like helicopter propellers.

Among them, the root wraps the seed body, and the other huge leaf veins have no reproductive function. When it falls from the branch, it will rotate during the falling process, which serves as the "clothes" of the seed.

Of course, without the blessing of wind, it cannot fly freely.

From a human perspective, dressing seeds in this strange "clothes" does not seem to be a cost-effective deal. After all, the chances of them being able to play a role are very limited, and samaras cannot fly long distances during the falling process.

In fact, the samaras are very light, especially after they are fully mature and dry. When blown by the wind, their huge "clothes" can easily move the seed body at the bottom and complete the flight close to the ground again and again.

Maple seed and its spinning falling state from above. Image source: Reference [3]

Of course, the unique appearance and flying posture of maple samaras have also brought a lot of inspiration to scientists.

For example, the rotating samaras have many similarities with the blades of rotating machines such as bamboo helicopters, electric fans, and wind turbines.

Samara may provide us with some reference ideas to help us design products with better aerodynamic performance.

In 2021, a team of scientists from South Korea, the United Kingdom, China, the United States and other countries proposed a micro-aerial vehicle.

They invented a tiny flying vehicle by studying various flying seeds and applying the principles of bionics.

It is equipped with a variety of sensors, which can rotate steadily and slowly during the falling process.

3D micro-aircraft invented by scientists. Image source: Reference [2]

03

The wandering of tumbleweed

In fact, the seeds of most plants are not as light as a swallow and cannot travel long distances relying solely on the wind.

In order to send its "children" on their final journey, after the seeds of the tumbleweed mature, the green and fluffy plants gradually turn yellow and curl up into a ball, and then the roots break.

Blown by the wind, the tumbleweeds rolled with the wind and gradually became rounder. During this bumpy journey, the tens of thousands of seeds they carried were also scattered in every corner along the way.

Tumbleweeds are also known as "desert tramps" and are a symbol of American Western culture along with cowboys and horse-drawn carriages.

However, if you have the opportunity to go to Antarctica, you may see a big snowball, but when the wind blows, it looks like a rolling "white tumbleweed".

Don't make a fuss, it's just a "Tumbleweed Rover".

This is a "balloon" developed by scientists to carry testing instruments based on tumbleweeds.

NASA scientists push a tumbleweed rover (not a snowball!). Credit: NASA

The Tumbleweed Rover was designed and built by NASA's Jet Propulsion Laboratory.

Compared with the ice and snow in the polar regions, due to the presence of various operating electronic equipment and the closed environment, the interior of the Tumbleweed Rover is kept at around 26.7°C, which is equivalent to a balloon filled with heated air.

The Tumbleweed Rover has excellent mobility. Even in extreme and remote environments, the Tumbleweed Rover can easily "roll" over rugged terrain and quickly complete data collection.

The interior of the Tumbleweed Rover is very complex, and all the instruments are fixed in a tube connected at both ends to prevent the instruments from being damaged or falling off during the rolling process.

During the movement, the global satellite positioning system carried by the rover can send its location, surrounding air temperature, pressure, humidity and other information to the ground research station in real time.

In recent years, NASA has been planning to develop the next generation of rovers, which will make full use of the Tumbleweed rover's airbag structure and use it as a parachute.

If all goes well, this new rover might one day also be aboard a spacecraft and roll around on the Martian surface.

The structure of the Tumbleweed Rover. Source: NASA Author's translation

04

Alien species: Invasion still needs accomplices

In the spring when everything sprouts, flowers compete for beauty and splendor. On the surface, it is the hardworking bees that are working hard to spread pollen. In fact, wind is the main force in spreading pollen.

With the help of wind, pollen has acquired the ability to "travel thousands of miles", which has played a significant role in promoting plant reproduction.

But on the other hand, for invasive alien species, wind is undoubtedly an accomplice, it expands the scope of harm and causes more terrible consequences.

In recent years, our country has been plagued by the invasion of alien species.

For example, ragweed, which was rampant in the early years, has strong ability to absorb fertilizer and regenerate. It can still regenerate after being cut many times. The plants are tall and strong, growing in groups, and are often difficult to eradicate.

Ragweed invades fields of various crops such as wheat, corn, and soybeans, consuming large amounts of water while absorbing nutrients from the soil, causing the soil to become dry and barren, seriously affecting crop growth.

In addition, ragweed pollen is the most important type of pollen allergen.

Whenever the pollen is in the air, people with allergies will experience symptoms such as asthma, sneezing, runny nose, and even other complications leading to death after coming into contact with ragweed pollen.

Copyright image, no permission to reprint

In response to these phenomena, scientists have started their research.

In fact, the spread of pollen is not without rules. Scientists have developed a mathematical model corresponding to the spread of pollen through experiments.

Through mathematical calculations, scientists can accurately predict the propagation path and range of an entire piece of pollen (not every single pollen grain), explore the movement patterns of pollen, and on this basis, take certain technical measures to effectively control the spread of pollen.

Of course, the transmission methods of small particles such as dust, pollutant particles PM2.5 and so on are similar to those of pollen.

Scientists have put a lot of effort into these small particles and developed many formulas that can predict their movement patterns to help people better deal with their hazards.

Conclusion

Unexpectedly, scientists have been able to come up with so many fantastic "black technologies" through these seemingly inconspicuous plants.

It seems that on the road to progress, we can never do without nature, our profound mentor.

References:

[1] Cummins, C., Seale, M., Macente, A., Certini, D., Mastropaolo, E., Viola, IM, & Nakayama, N. (2018). A separated vortex ring underlies the flight of the dandelion. Nature, 562, 414-418. https://doi.org/10.1038/s41586-018-0604-2.

[2] Kim, BH, Li, K., Kim, JT. et al. Three-dimensional electronic microfliers inspired by wind-dispersed seeds. Nature 597, 503–510 (2021). https://doi.org/10.1038/s41586-021-03847-y

[3] Dong Lin, Wen Guoan, Lei Ziwei, et al. PIV experimental study of vortex system during the spinning falling process of seed leaves[J]. Experimental Fluid Mechanics, 2021, 35(5): 54-60.

[4] https://www.nasa.gov/missions/earth/f_tumbleweed.html

Produced by: Science Popularization China

Author: Cheng Mingchen

Producer: China Science Expo

The cover image and the images in this article are from the copyright library

Reproduction of image content is not authorized