In autumn, the decrease in daylight hours and the drop in temperatures cause a gradual halt in photosynthesis. The leaves then produce less chlorophyll, revealing other pigments such as carotenoids (yellow and orange) and anthocyanins (red). It is this change in pigments that gives leaves their autumn colors.
The green color of the leaves is mainly due to the presence of chlorophyll. This pigment absorbs sunlight to carry out photosynthesis and produce the energy essential for the tree. In autumn, the production of chlorophyll decreases and then gradually stops. As it disappears, other pigments take over. The bright yellows and oranges mainly come from carotenoids, pigments that are already present but masked until then by the green. As for the reds and purples that sometimes illuminate the leaves, they come from anthocyanins, pigments produced only in autumn under certain climatic and environmental conditions.
The climate plays a key role in the timing and intensity of the color change in leaves. As the days shorten, the decrease in light gradually triggers the cessation of chlorophyll production, revealing the hidden pigments. Cool (but not freezing) and sunny nights particularly favor intense colors, with stunning bright reds and oranges. Conversely, a rainy, mild, and overcast autumn will produce duller shades. A strong summer drought can even lead to early leaf drop, limiting the autumn spectacle.
During autumn, trees prepare for the cold season by slowing down their internal processes. They begin by gradually decreasing the production of chlorophyll, the pigment responsible for the green color of leaves, which is essential for capturing light and performing photosynthesis. As this chlorophyll fades away, other pigments naturally present in the leaves, such as carotenoids (yellow and orange) and anthocyanins (red and purple), become visible. A layer of cells called the abscission zone forms at the base of the leaf, slowly cutting off the supply of water and nutrients. Gradually deprived of water and chlorophyll, the leaves stop their photosynthesis, reveal new colors, and eventually fall off.
Trees do not all play on the same team in autumn. The maples, for example, often turn to bright reds or brilliant oranges thanks to their abundance of anthocyanins, those pigments that provide warm and vibrant colors. The oaks, on the other hand, prefer to display more subdued shades, often brown, dark red, or coppery brown. As for the birches, ginkgo, or even the poplars, they tend to lean towards bright yellows, thanks to the pigment called carotenoid, which is dominant in them. The needles of conifers like pines or firs remain true to their green color, protected by their waxy coating and a different chemical composition. In other words, each species plays its own autumnal tune.
Did you know that cool nights combined with sunny days are ideal for producing particularly vibrant autumn colors? This climatic contrast promotes the development of red and orange pigments.
The leaves do not simply fall due to the wind: the tree actually produces special cells that form an abscission zone, thus creating a break point that naturally promotes their fall.
Contrary to popular belief, it is not just the arrival of cold weather, but rather the gradual decrease in daily sunlight hours that first triggers the process of color change and leaf drop in trees.
Some pigments like anthocyanins, responsible for red and purple hues, only appear in the autumn, partly to protect the leaf from UV rays and thus extend its photosynthetic activity.
No, only deciduous trees change color in autumn. Evergreen trees, like pines or firs, keep their green leaves or needles all year round.
The leaves contain different pigments that influence autumn colors. Carotene provides yellow and orange tones, while anthocyanins produce red or purple shades depending on the species and environmental conditions.
Yes, cool nights combined with sunny days promote vibrant colors. In contrast, mild temperatures or a dry autumn can make the colors more dull and less spectacular.
Yes, early frost attacks damage the leaf tissues, accelerating their premature drop, sometimes resulting in a decrease in the intensity of autumn colors.
The shedding of leaves allows deciduous trees to minimize their water loss during winter and conserve the energy needed for their survival during difficult periods when light and water are limited.
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