Why Do Leaves Appear Green? Interesting Facts For Curious Kids | Kidadl


Why Do Leaves Appear Green? Interesting Facts For Curious Kids

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Have you ever wondered why the majority of plants are green in color? 

Every plant appears green because of the presence of a chemical called chlorophyll. Chlorophyll is a pigment in a plant cell that performs chemical reactions in plants and is especially known for making plants appear green.

Chlorophyll is a chemical molecule found in cells of plants called chloroplasts, which absorb light from the sun to convert it into sugars, or glucose, which nourish the trees. This process is called photosynthesis. The excess sugar is converted into starch and stored within the cells for future use. It absorbs red light and reflects green light, which gives the leaf its color. Stomata are parts of the leaf known as the ‘guard cells.’ Their important function is to control the moisture or water level inside the cell. The shape of the stomata is like two small kidney-shaped doors, which open and close like our eyes to contain or release the moisture within the cell as a response to external stimuli. Hence they have been named as guard cells of the plant. These eyes-shaped cells also protect the cells from bacteria, extreme conditions, and harmful light. Chlorophyll aids in the metabolism process of the plants, while stomata help in respiration.

After reading about why all plants in the world appear green, you may also like to know why do judges wear wigs and why do we say the pledge of allegiance.

What is the scientific reason behind the green color of leaves?

Plant leaves appear green mainly because they contain chlorophyll pigment in the cells called chloroplasts. These cells absorb sunlight. During the process called photosynthesis, plants absorb sunlight and convert it into energy and release oxygen. Chlorophyll plays a central role by letting in the right type of visible light, which is mainly blue light and red light, absorbing these short and long wavelengths of white light and reflecting the unnecessary green light, giving the leaf its green appearance.

Plants convert the energy from sunlight into sugar, glucose, or starch which serves as food for the plant and is essential for its nourishment. But this process can only take place when the sun is out, as sunlight is the most important element for the chemical process. During this process, the chlorophyll pigment in the leaves of a plant absorbs certain wavelengths of light while other wavelengths of light are reflected. As we know, visible light is made from a spectrum of seven colors, measured by its wavelengths. As we move from red to purple on the spectrum, the wavelengths reduce gradually. The plants mainly need the red wavelength of light, which is the longest, and expels the green light which it does not need. Green light is reflected from these pigments and absorbs other wavelengths, making the leaves appear green in color. Therefore, the green color of plants can be attributed to the process called photosynthesis. Chlorophyll is one of the main ingredients required for the photosynthesis process to be completed in a plant allowing the conversion of light into energy.

Are all leaves green in color?

Not all leaves are green. You've probably noticed some plants with red or yellow leaves around you. Even though the majority of plants have green leaves, it is not an absolutely necessary factor for every plant. Plants and their leaves come in diverse colors.

As we have already seen, leaves are the most essential part of the survival mechanism of a tree’s life. As winter gives way to spring, trees begin to grow green leaves with all their colors again. How and where do trees store the energy to grow new leaves after winter?

During autumn, a chemical process called abscission takes place in plants whereby the trees produce abscisic acid in a chemical reaction. In this process, the trees’ metabolism system is slowed down due to a lack of bright sunlight. The trees start shedding their leaves to conserve energy and water within their cells. Abscisic acid is released, which severs the hold between the leaves and branches, making the leaves fall. As the tree does not have to nourish its leaves anymore, the energy is saved. During winter, these cells work on a minimal level, only to keep the tree alive and healthy and stopping the growth process. When spring comes back with abundant sunlight, these cells reactivate and use whatever energy they had conserved before last fall season to grow leaves and fruits, and flowers until the next fall, when the cycle repeats.

How do birds and animals see plants?

Birds are known to be tetrachromats which allows them to view the ultraviolet colors along with the red, blue, and green light. Humans are trichromats which means we are able to sell only three colors, red, blue, and green. UV has no color of its own, but it does allow the birds to see a whole spectrum of colors that humans are unable to see. As such birds are able to see plants in a different color than what humans can do. This same ability extends to bees and butterflies as well.

But the vision of animals works in a different way. Cats, mice, rabbits, and dogs are able to see only blue and yellow along with some shades of grays. The same is the case with most mammals in the world. Most species of snakes like vipers can only use thermal sensing to view plants and other animals. As such, different animals will see light reflected from plants in different ways.

Why do leaves change color?

Nature view of tropical green palm leaves.

Did you know that plants turn the carbon dioxide in the air into oxygen through the process of photosynthesis?

Many trees tend to change colors from green and shed leaves in the autumn season. The main reason is inadequate sunlight. As the chemical reaction changes in the leaves, the amount of chlorophyll reduces, giving rise to other pigments like carotenoid or anthocyanin instead. These pigments are mainly responsible for coloring the plants red, orange, yellow, or purple as it reflects these colors.

During autumn or fall, the daytime is reduced drastically and nighttime increases as the sun sets earlier and rises later. This causes the plants to produce less food for themselves, further causing a reduction in photosynthesis and intake of carbon dioxide, which reduces the amount of chlorophyll pigment in the plant. This causes them to lose their green color and turn orange or yellow instead. Some trees may also take on red or purple colors. As the production of food stops, these trees slowly start to shed their leaves and that is why you see leaves change color in the fall.

Why are some trees evergreen?

Have you wondered during Christmas, when a number of trees are bare with no leaves on them, how do some trees keep their green leaves? One of the main reasons for trees staying evergreen is the needle-like leaves of trees like pine, cedar, and fir.

The loss of adequate sunlight equally affects coniferous trees, or these short needle-leaved trees, too. However, they do not completely lose their chlorophyll as much as other deciduous trees around us do. That’s because these trees have evolved in colder climates with high altitudes with less carbon dioxide, meaning less water and less sunlight to survive on. Getting less sunlight, these trees learned to survive by conserving these energy resources in their tightly woven needle-like leaves. During winter, the sunlight and water reserved in the chloroplasts of these trees help them to survive through long stretches of insufficient sunlight and maintain their colors. The waxy exterior of these leaves helps to keep the water molecules safely inside the cells until spring season comes. Nevertheless, if these trees fail to get bright sunlight or water for an extended period of time due to natural calamity or extremely bad conditions, they too start to lose their color and shed their leaves. 

Chlorophyll is an essential part of the process of photosynthesis, which absorbs sunlight for the plant’s nourishment through the production of glucose to give a plant the energy required. What if a plant does not have green chlorophyll pigment at all, for example, plants with a number of leaves that are purple or red in color most times of the year?

This question is what makes scientists still wonder. Some leaves which are visible as red, purple, or yellow still have some chlorophyll present in their systems, which absorbs light from the sun and produce sugars like glucose even though it may not be visible to the naked eye. This could be possible due to the presence of certain pigments other than chlorophyll. A pigment called carotenoids absorbs blue light instead of red and reflects yellow, orange, or red light. If this pigment is present in greater quantities than chlorophyll, the plants appear to be yellow, orange, or red respectively. In such cases, metabolism is usually not affected if these plants receive proper sunlight, as they have different chemical reactions compared to other plants. These plants have adapted to survive with less chlorophyll and more carotenoids, hence their growth may be affected in some ways but won't be completely hindered. But overall, chlorophyll is essential for the survival of plants.

Here at Kidadl, we have carefully created lots of interesting family-friendly facts for everyone to enjoy! If you liked our suggestions for why do leaves appear green, then why not take a look at why do we pay taxes or why do men grow beards?

Written By
Supriya Jain

<p>As a skilled member of the Kidadl team, Shruti brings extensive experience and expertise in professional content writing. With a Bachelor's degree in Commerce from Punjab University and an MBA in Business Administration from IMT Nagpur, Shruti has worked in diverse roles such as sales intern, content writer, executive trainee, and business development consultant. Her exceptional writing skills cover a wide range of areas, including SOP, SEO, B2B/B2C, and academic content.</p>

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