Have you ever wondered why maple leaves turn red while leaves of trees like poplars and ginkgos turn yellow?

In fact, the color of fallen leaves depends on the dominance of three factors:

1. Chlorophyll:

Within chlorophyll, there are many different variants. Among the most common in higher plants are chlorophyll a and chlorophyll b. They are insoluble in water but soluble in organic solvents such as ethanol and acetone.

Chlorophyll in plant tissues primarily participates in the process of light absorption during photosynthesis. It absorbs most red and violet light while reflecting green light, hence the green color of chlorophyll. The synthesis of chlorophyll requires strong light and high temperatures, but it is also unstable.

Factors such as light, pH, and oxidants can decompose chlorophyll. In spring and summer, the synthesis of chlorophyll exceeds its decomposition, allowing for timely replenishment of decomposed chlorophyll. However, in autumn and winter, the synthesis is insufficient, leading to an imbalance and subsequent decline in chlorophyll levels. This is why leaves turn green in spring but lose their green color in autumn.

2. Carotenoids:

Let's delve into "carotenoids." There are two main companions here: carotene and xanthophyll. Like chlorophyll, they are insoluble in water but soluble in organic solvents.

During photosynthesis, they primarily absorb blue and violet light, assisting chlorophyll in capturing light energy. Carotenoids are relatively stable compared to chlorophyll and are less affected by external environmental changes. Therefore, when the chlorophyll content decreases in autumn, the proportion of carotenoids increases accordingly, resulting in the yellow coloration of leaves.

3. Anthocyanins:

Anthocyanins have a large family, with over 300 siblings in the natural world.

The vibrant colors of flowers, fruits, and vegetables are often attributed to accumulated anthocyanins. Anthocyanins in cells mainly exist in vacuoles. They are colorless but exhibit different colors when dissolved in water under varying pH conditions.

In late autumn, as temperatures drop, leaves' ability to transport sugars and water decreases. Glucose accumulates, leading to higher concentrations. Increased soluble sugars make cells acidic, causing anthocyanins to turn red under acidic conditions, resulting in the red coloration of leaves.

Autumn arrives, leaves gently fall, and it's beautiful. Besides aesthetics, do you know the various uses of fallen leaves?

So far, the utilization of fallen leaves has been limited. They're either left on the ground, composted, or burnt, resulting in waste and environmental impact.

However, fallen leaves are rich in pigments and beneficial compounds, so not utilizing them would be a waste.

Researchers at VTT Technical Research Centre of Finland have developed several methods for processing leaves, which can be used in cosmetics, textiles, as well as the feed and food industries. It's astonishing how versatile fallen leaves can be, let's delve into their potential!

The colors of autumn leaves come from orange and yellow carotenoids and red anthocyanins.

Currently, there is a rapidly growing demand worldwide for natural pigments. These natural pigments can even promote human health and be used as health supplements.

Apart from pigments, fallen leaves contain many beneficial compounds such as phenols, lignin, carbohydrates, and proteins.

In a study conducted at VTT, researchers collected fallen leaves from gardens and parks, processed them through drying and grinding, and extracted the desired compounds. This process carried out in VTT's laboratory, has advanced to the pilot stage, using raw materials collected by waste management company Lassila & Tikanoja in the Otaniemi area. Researchers pay close attention to the environmental friendliness of the entire process and the safety of the products.

"In the lab, we've discovered several methods for utilizing leaves. At the same time, we're conducting semi-industrial trials to test whether our methods can be applied in practical work and how many valuable compounds can be extracted from leaves," commented VTT Senior Scientist Liisa Nohynek.

Autumn is a feast of nature, brimming with vitality and change. Behind the falling leaves lies a wealth of chemical secrets and endless possibilities.

Through in-depth research and utilization of fallen leaves, we can not only reduce the environmental burden but also develop more beneficial products. These efforts not only signify efficient resource utilization but also serve as a tribute to the gifts of nature. May our exploration and innovation bring a brighter future for humanity and the Earth.