Why do leaves change color? (Chlorophyll Effect)

In Autumn, the green leaves turn yellow, orange, red, and then brown! What is the logic for this colorful miracle of nature? According to recent studies, “the color of a leaf is subtractive, like the shades of pastels on paper.” 

The green color of the leaves comes from chlorphyll, a green pigment contained in tiny bags: chloroplasts. Every year, it is the same conflagration: the deciduous leaves die little by little, passing from green to yellow and orange, each time offering us exceptional landscapes. But how to explain this change of colors and why do the leaves change color in the fall? 

To solve this mystery, we should watch this excellent presentation created by The American Chemical Society (ACS) and podcasted by the Reactions in YouTube. This show reveals the chemistry all around us; and answer the curious questions we always wanted to ask!

Watch out one of its great episodes to discover and learn a nature’s play…

In this nature-chemistry video, Reactions is sharing some seasonal science facts behind – Leaves Changing Colour.  

We observe and how the narrator explains, that from the first day of fall, the telltale signs that we can feel: such as crispy-weather, pumpkin spice lattes (the most popular seasonal menu in western lands), and the most importantly, secret behind the changing colors of leaves.

Did you ever imagine why some leaves turn yellow, others orange or red, and some of them become brown? It’s all due to the green photosynthetic pigment termed chlorophyll, plus the glucose deposited inside the trees that help to expose the reds, yellows, and golden browns of autumn foliage. 

Chlorophyll: The Engine Of Photosynthesis

All green parts of a plant, including green stems and fruits that are not yet ripe, carry chlorophyll. However, it is the leaves that hold the most; chlorophyll absorbs sunlight and converts it into nutrients for the plant. 

This process, which is called photosynthesis, takes place at the level of microscopic pores located mainly in the tissues of the green leaf, the stomata. The manner of photosynthesis also consumes carbon dioxide (Co2) and releases oxygen (O2).

In simple words, plants need sunlight, nutrients, and water to grow. The nutrients and the water was coming from the ground; while the leaves capture the sunlight. 

The leaves use a chemical called chlorophyll to capture sunshine. Chlorophyll is the pigment that makes the leaves green. Through a process called photosynthesis, chlorophyll transforms sunlight into energy that plants need to grow.

A Change Of Color In The Fall

Chlorophyll gives a green color to the leaf. It is not the only pigment, which is present in the chloroplast, but others are invisible in regular days because the chlorophyll is truly dominant. Those are: 

●     Carotenoids – orange and yellow.

●     Xanthophyll – yellow

●     Anthocyanins, Ranges from blue to purple.

In Autumn, with the change in climatic conditions (return of freshness and more heavy rains), the trees gradually enter into vegetative rest. The chlorophyll then degrades, and its concentrations decrease. The other pigments are thus exposed, which sometimes also considerably changes the colour of the leaves.

Great To Know: Lists Of Trees And Shrubs With Beautiful Fall Colors

Depending on the concentration of each of these pigments, specific to each species, one can marvel at colors ranging from golden yellow to purple, through many shades of orange, red…

Here is a list of the shrubs and trees with the most beautiful fall colours:

●     For golden yellow colours: maple, birch, Cotinus, dogwood, ash, pheasant tree, tulip tree, Robinia and Acacia, Ginkgo biloba;

●     For orange-yellow or red-orange colours: many Japanese maples, Callicarpa, hornbeam, male dogwood, wig tree, American honey locust, witch hazel, liquidambar, Persian Parrotia, sumac, many flowering cherry trees, rowan, spirea;

●     For red colours: many Japanese maples, barberry, Canadian sheath, dogwood, Cotinus, Cotoneaster, winged charcoal, Nandina, some flowering cherry trees such as Kojo-no-mai, flowering pear, marsh oak and its red cousin, rowan trees, red vines;

●     For purple colours: some Japanese azaleas, some certain varieties of Berberis, Leucothoe Scarletta, oak-leaved hydrangeas, liquidambar, viburnums, etc.

Summing-up

● In the presence of light, the green parts of plants produce organic matter and oxygen from carbon dioxide;

● In the Autumn or fall, when the chlorophyll breaks down, the different shades of yellow, orange, red and purplish pigments are revealed.

Fascinating: How To Separate Pigment Molecules From The Leaves?

Kids, to understand it, you need to perform Chromatography, a chemist’s trick to separate molecules.

By this experiment, you can witness the presence of several colors on the strips of paper. For chromatography, you need a liquid (the solvent), which is “mounted” in the paper; now take it with the different colored pigments present in the leaves. These pigments are not going to climb at the same rate. So, you will see various shades of different colors. But, you also need to separate the colors, and then you will see colors appear that you could not see before. 

Hope you relished this nature’s science stuff and experience and also enjoyed the discussion about Why Leaves Change Colors! We will meet again with another fascinating post, till then keep exploring the science world with us! 

Interesting Nature / Plant Science Activities:

Respiration in Plants – Live Proof

Why Flowers Change Color

Spore Printing with Mushroom

Compare Different Seeds – Nature Science Study

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