Why are there no two identical leaves in the world? Here comes the truth!

Why are there no two identical leaves in the world? Here comes the truth!

Author: He Zhentian Popular Science Writer

Reviewer: Liu Guangyu, Senior Engineer, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences

Every leaf has the same mission: to harvest energy from sunlight.

Plant leaf cells are filled with chloroplasts, organelles that contain chlorophyll. Chlorophyll converts sunlight, water and carbon dioxide from the air into sugars as nutrients for plants and releases oxygen in a process called photosynthesis. Photosynthesis is extremely important for plant growth, and almost 90% of the nutrients needed by plants come from it. However, have you ever wondered why plants grow leaves of different shapes in nature if the main task of leaves is so similar?

The answer lies in the environment in which the plants live.

The shape of leaves of different plants has evolved over many generations, mainly influenced by the light and precipitation in the environment. Other factors such as wind, temperature, soil, and even herbivores also have a certain shaping effect on the shape of leaves. In addition, plants have different energy needs at different growth stages, and therefore have different requirements for the efficiency of photosynthesis, which may also affect the shape and size of leaves.

In plants of different species, the relationship between the environmental characteristics of the growing area and the shape of the leaves is most obvious.

For example, trees living deep in the forest are always blocked by taller neighbors, and sunlight rarely shines down. How do they survive in this shaded place? That is to grow broad and flat leaves. Broad leaves are like outstretched hands, so that plants can catch every ray of sunlight that falls through the gaps. But broad leaves are also more likely to lose water, so plants with broad leaves are more likely to appear in humid areas. Tropical rainforests are a good example. After all, there is plenty of rainfall there, and you can spend it as much as you want. Beech, which also grows in rainy areas, even has unique grooves on its leaves, which can effectively drain water and prevent water from staying too long and causing damage to the leaves.

Yunnan banana in Xishuangbanna has broad leaves.

Wild Monstera in the rainforest often grows larger leaves than domestic Monstera

The humid and rainy marine climate is most conducive to the growth of European beech.

Their gutter-covered leaves are well suited to handling continuous rain.

On the other hand, the leaves of trees that grow in places with scorching sun, dryness and little rain look different. The leaves of these trees are slender and needle-like, and this shape effectively reduces water evaporation. With a layer of waxy outer shell, it is like wearing a well-designed "sunscreen jacket", which can not only protect itself from sunburn, but also reduce the loss of water in plants in an environment with scarce water sources. Not only that, the slender needle-shaped leaves can also help trees withstand the test of heavy snow and strong winds, making it difficult for trees to fall.

Norway spruce grows in Arctic regions and has clusters of needle-like leaves. They are also commonly used as Christmas trees.

The larch trees in Daxinganling turn golden and shed their leaves every autumn.

Their leaves appear to be fine and velvety, but are actually very stiff.

The sawdust on the edges of the leaves can promote transpiration and photosynthesis. The young leaves of birch trees growing in cold regions often have denser serrations, which helps them to efficiently transpire and drive the flow of nutrients, allowing them to grow faster in a short growing season.

Young birch leaves

There are no two identical leaves in the world; each unique leaf is a historical record of a plant's active adaptation to the environment.

Author: He Zhentian Popular Science Writer

Reviewer: Liu Guangyu, Senior Engineer, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences