Why can the leaves of Victoria amazonica hold up a person? In fact, it has been working hard "behind the scenes"

"A lotus leaf floats on the water, and a real person sits firmly on the boat." When I saw this poem as a child, I was always puzzled. How could a lotus leaf be so big that a person could sit on it? This must be the "exaggeration" rhetoric device that the teacher mentioned in class, until I saw the Victoria amazonica in the botanical garden one day.

Although the plant on which the immortals are feasting in the poem is definitely not the Victoria amazonica native to South America, its huge leaves are indeed large enough for children and even adults to sit on.

A child sitting on a Victoria amazonica leaf. Image source: kew.org

So, what is the secret of Victoria amazonica leaves that can withstand such unexpected weight?

The secret behind the leaves of Victoria amazonica

The Victoria amazonica has long fascinated scientists, architects and artists with its giant leaves and extraordinary load-bearing capacity, but how its leaves can grow to 2-3 meters wide and support the weight of a child or even an adult has remained a mystery until now.

A recent study published in the journal Science Advances answered this question. Researchers found that the secret of Victoria amazonica's super-strong load-bearing ability may be hidden on the back of its huge leaves.

When people see Victoria amazonica in botanical gardens or in the news, they usually see the front of its leaves. From the front, the Victoria amazonica leaves look like a huge dinner plate with upturned edges. During the growth period, the Victoria amazonica leaves will rapidly expand outward every day until they are fully grown. According to the China Flower News, if there is enough space, a single Victoria amazonica plant can cover an area of ​​20 to 50 square meters.

Photo: Photographed by the author

If we cut off the petiole of the Victoria amazonica leaf and turn the leaf over, we will see a completely different scenery. Unlike the emerald green on the front of the leaf, the back of the Victoria amazonica leaf is purple-red with many hard thorns and radiating network-like veins.

The back and front of the Victoria amazonica leaf. Image source: kew.org

As you may have guessed, the crisscrossing veins on the back of the Victoria amazonica leaf are the secret of its ability to carry people without sinking. Imagine that if a leaf is to carry a certain weight without sinking, it must have a certain mechanical strength and the biomass cannot be too large (too heavy will sink directly). The veins of Victoria amazonica perfectly solve the above two problems.

The structure of the leaf veins of Victoria amazonica. Image source: References

Unlike many plants that we see everyday, the veins on the back of the Victoria amazonica leaf are very strong, showing plate-like bulges, and crisscrossing to form small square grids. Not only that, from the overall perspective, the plate-like veins radiate from the petiole to the surrounding area, forming a net-like distribution, evenly covering the entire leaf, looking like a very solid skeleton.

In fact, this is exactly the case. Scientists conducted field experiments and mathematical modeling analysis on such structures and found that compared with the leaves of water lilies, the special structure of Victoria amazonica leaves enables them to have higher structural strength at the same weight.

Mathematical modeling of the leaf structure of Victoria amazonica Image source: References

In addition to its high structural strength, the thick veins of Victoria regia also have many gaps filled with gas, which provide huge buoyancy. The combination of the two allows Victoria regia to float on the water with people on board.

The big leaves are not for carrying people, but for survival.

Seeing this, I wonder if you are curious about one thing, why does the Victoria amazonica have such large leaves? Although the large leaves of Victoria amazonica can carry people, it is definitely not for people to sit on them.

So how did Victoria amazonica become a giant in the water? It all started with the environment in which it lived.

As mentioned earlier, Victoria amazonica is native to South America, and the species diversity in tropical regions is extremely high, and the interspecific competition among different species is also relatively strong. If you want to stand out in such an environment, you must have something unique.

Victoria amazonica and other plants complement each other. Image source: powo.science.kew.org

As we all know, plants rely on leaves to carry out photosynthesis, but the leaves of plants cannot increase endlessly. Their size is limited by the mechanical strength of the leaves. There is no point in growing big. If they have no strength, they will eventually be blown away by the rain and wind.

Scientists speculate that the structure of Victoria amazonica allows them to grow large and very strong leaves with a small biomass, thereby capturing more sunlight for photosynthesis, which may be the secret of their success.

Just imagine that in a pond in the wild, the huge leaves of the Victoria amazonica grow rapidly and spread out on the water surface, competing for precious space on the water surface and blocking the light, leaving no way for any other plants under the leaves to move. Doesn't it give you a sense of déjà vu of a "plant bully"?

Young leaves of Victoria amazonica Image source: BBC

In fact, in addition to its size like a "bully", the "equipment" on its body also makes it look not very kind. As mentioned earlier, the back of its leaves is covered with thorns. These thorns make the young leaves of Victoria amazonica that have just emerged from the water look like "hedgehogs" that strangers should stay away from. They can effectively prevent fish from eating the leaves. These thorns will also "punch" the surrounding areas as the leaves grow, forcing the surrounding plants to retreat.

To sum up, high intensity and low cost give Victoria amazonica an advantage in the "war" with other plants for space and light. Perhaps this is the wisdom of plants.

The leaves of Victoria amazonica gradually grow. Image source: plantwerkz.blogspot.com

Extracting knowledge from the wisdom of plants

In fact, the function of Victoria amazonica is far more than just carrying people. People have learned a lot from the structure of its leaves, especially architects.

In 1851, a tall building in Hyde Park, England, caused people to marvel: "Such a beautiful house can be built with steel and glass." What was even more surprising was that the designer of this building was a gardener, Joseph Paxton. Paxton was responsible for the cultivation of Victoria amazonica. It is recorded that Paxton once placed his daughter on the leaves of Victoria amazonica and found that the leaves were intact. This gave him inspiration to complete the design of the venue.

Paxton's daughter stands on a Victoria amazonica leaf. Image source: virtualherbarium.org

As the venue for the first World Expo, this venue was known as the "Crystal Palace". Queen Victoria wrote in her diary: "Through the iron gate, I saw the top floor of the church, countless waving hands, flowers, statues and corridors crowded with people. After entering the hall, I heard the loud trumpets. This feeling is unforgettable. I was extremely excited. I saw how magical, magnificent, brilliant and shocking the beautiful crystal fountain was. As I have told people many times later, my heart was full of piety that day. It is difficult for any other ceremony to make people feel this way." (Note: The diary content is quoted from a report by Phoenix TV)

There is no doubt that the structure of Victoria amazonica leaves can bring a lot of inspiration to architects. The bionic load-bearing structure designed with reference to its leaf structure has stronger resistance to deformation and can also withstand heavier weight.

Bionic load-bearing structure designed with reference to Victoria amazonica leaves Image source: References

Seeing this, do you want to feel the charm of Victoria regia up close? Considering the characteristics of Victoria regia flowers that open in the evening and close in the morning, tourists who want to watch them should pay attention to the flowering time. In the hot summer, it is best to appreciate Victoria regia in the evening. Maybe you will get some inspiration from it!

References:

Box, F., Erlich, A., Guan, JH, & Thorogood, C. (2022). Gigantic floating leaves occupy a large surface area at an economical material cost. Science advances, 8(6), eabg3790.

Produced by: Science Popularization China

Author:EVEE

Producer: China Science Expo