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Some of our visitors have sent emails with interesting questions, we decided to start having a space to answer them. In this space the blog "Restless Minds" will answer all questions you send us
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Science progress affects our daily life and "to know" means you are going to chose right, because it allows you to form your own opinion on scientific everyday issues. On the other hand, having an elegant and harmonious vision of the world where we live in leads to a feeling of intellectual satisfaction.
We believe this kind of scientific day to day knowledge should be encouraged from an early age, and that's why this project was born: science, culture, knowledge, crafts for your restless mind.

Wednesday, November 9, 2011

Autumn colors- answer to reader

Marco send us an email, he wants to know why in the autumn leaves are not all the same color:

"Hello, leaves are yellow here where I live, but i saw pictures from another places where the trees have brown, yellow, red leaves... I want to know why leaves dont have those colors here."

Marco, the thing is leaves color is determinate by several variables.

First lets see how it works.

Leaves work as natural factories for nutrients.
Using roots, plants get from the soil all nutrients and water (H2O) they need to live. From the air they get carbon dioxide (CO2). With sun light help they transform CO2 and H2O in Oxygen (O2) and glucose, without them the live as we know it, would not be possible.
Glucose is a sugar, and plants use it as a source of energy, allowing the plant to grow this transformation process is called photosynthesis.
Chlorophyll is a pigmented molecule and has a active role in photosynthesis. Chlorophyll gives the green color to the leaves and, even more important, they absorb sun light and therefore make possible the growing process.

How do leaves change color?
When summer ends and the fall begin, days become shorter. This fact works for plants as a trigger to begin preparing to the winter cold- like other living things.

During winter, there isn't enough light to carry out photosynthesis. Trees get in "stand by" mode and they will live from summer stocked nutrients, slowly the nutrients factories turn off the production. Green Chlorophyll vanishes from leaves. This changes lead to a kind of migratory process of nutrients from leaves to stem; here they will be protected from the winter cold. That way, later when spring arrives, those will be used to form new leaves, and the process will repeat itself
As the nutrients migrate to a safe place, leaves stop producing chlorophyll, and the green start to vanish. This allows other pigments to show their colors, like yellow, brown, red, etc, in fact this colors always been there, they just were not visible in the Summer, because chlorophyll concentration were to high.

Why so many colors?
The range of fall colors is enormous, some of them are hereditary, different tree species show different colors sets, and others depend on temperature range.

Vivid colors can be seen in places with great luminosity but with low temperatures (0 to 7ºC). England, for instance, where the fall is rainy but with temperate clima, leaves show yellows and cloudy-browns.
As winter approaches colors fade away and leaves fall from the trees.
After falling from the tree, leaves can't get water or nutrients and slowly dry, and lose all the rest of pigments.

Marco, you live in a place where the type of trees and the characteristic temperature of your autumn are suitable for yellow colors (probably carotenes- identical to those on carrots).
In other places red colors, scarlet or purple indicate the presence of anthocyanins, this pigments are only formed when the temperatures goes down a bit more.

References: internet images;

Et Voilá!
Autumn full of color


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