WHY DO THE LEAVES TURN YELLOW AND RED?

Knowledge from the fourth grade

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Recently with my daughter and was watching an educational program for the 4th grade in high school. In a thin voice, the girl on TV asked a question: Why do you think the leaves turn yellow in the fall of 2020?

And really, I thought, you go walking in the fall. Under your feet a fiery carpet of different colors: yellow leaves, red leaves, sometimes green leaves. In late fall, the leaves are already shriveled up and turned brown. But why the leaves turn yellow was not explained to us, even in preparation for the regional biology Olympiads!

Next the girl presenter with a happy face said that we apparently did not know the correct answer. And she explained. Everything brilliant is simple!

It turns out why there are so many fallen leaves in the fall: in summer the leaf is covered with the thinnest layer of wax, especially on trees. You can see this white patina on the leaves of most light-loving plants. In winter, look closely at your houseplants – this patina is especially visible on the thick, “fleshy leaves.” In the fall, this layer of wax is sucked from the leaf by the tree itself. For a tree, wax is an extremely valuable, irreplaceable resource. It is foolish to lose it along with the leaves. Left unprotected, the chlorophyll in the leaf breaks down and makes room for other pigments. These pigments were previously suppressed by chlorophyll, but after its destruction they show themselves, including by coloring the leaf.

But why do leaves turn yellow or red? Why do they fall off in the fall?

Leaf color in the fall depends on the trees, primarily on the genetic traits of the trees. Sometimes there are red, yellow, orange and green leaves on the same tree.

Leaves fall, however, as various heavy elements accumulate over the spring and summer and actually become heavier. A special tissue is formed at the base of the leaf petiole that rejects the leaf and it will fall anyway. Either by thunderstorm, wind, precipitation or other physical action, or by itself when the tree completely rejects the leaf.  

Why do leaves turn yellow or red? Why do they fall off in the fall?

WHY DO THE LEAVES TURN YELLOW AND RED?The color of leaves in the fall depends on the trees, primarily on the genetic features of the trees. Sometimes there are red, yellow, orange and green leaves on the same tree.

Leaves fall, however, as various heavy elements accumulate over the spring and summer and actually become heavier. A special tissue is formed at the base of the leaf petiole that rejects the leaf and it will fall anyway. Either by thunderstorm, wind, precipitation or other physical action, or by itself when the tree completely rejects the leaf.

But we still haven’t fully answered the question: why do leaves, regardless of size, also have different colors in the fall? It’s simple. Leaves contain anthocyanins. They are responsible for the red color. You can see this pigment in the leaf edges or flower buds. Anthocyanins produce red hues in a variety of colors. This is why fallen foliage comes in both bright red and burgundy and pale.

There are Carotenoids in the leaves. They are responsible for the orange color. In its pure form, it is probably only in flowers. But in the fall, when chlorophyll stops suppressing this pigment, leaves turn bright orange and shades of orange.

Finally, the pigment xanthophyll is responsible for the most common yellow color. This pigment protects the leaf and, at the same time, colors it yellow. This color, in addition to flowers, occurs in algae. In animals, on the contrary, it is extremely rare.

The predominance of one or the other color is precisely the predominance of one of the pigments in the composition of the leaf. All these pigments and chlorophyll are derivatives of the same protoplasts which change their chemical composition and color under the influence of sunlight.

Can yellow turn back into green, for example? Easy: take an orange or yellow carrot growing in a bed or potato and try removing the soil from the top. After a week or two, the part of the carrot or potato that has been exposed to the sun’s rays will turn green.

If the leaves of indoor plants turn yellow, however, this is most often a cause for concern: inadequate watering, a lack of minerals, or some kind of disease. On the other hand, whatever you do, sooner or later the leaves will yellow and fall off. This is inevitable.

Don’t feel sorry for the falling leaves. This is a biological mechanism. This way the tree gets rid of unnecessary substances, reduces its consumption of water and minerals for the winter, reduces water evaporation and renews itself.

Fallen leaves are better not burned, but collected in compost pits. Next spring it can be put under greenhouses and greenhouses and in the process of decomposition and decomposition old leaves will give the necessary and so insufficient in the spring heat. Next fall it will make excellent humus. 

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