Why are leaves green? Chlorophyll in leaves

CachHayNhat - You don't know why the leaves are green? Or why do the leaves turn yellow in autumn? Leaves are usually green, but not many people know the reason why leaves are green. Now let's discover the answer with CachHayNhat.

Why are leaves green?
Why are leaves green?

Why are leaves green and not any other color? Why do leaves turn yellow in autumn? Does the color of green have any important role? Why are some plants without green leaves? All of the above interesting questions will be answered by us right now.


1. Why are leaves green?

2. Why is chlorophyll green?

3. Chlorophyll

3.1. What is chlorophyll?

3.2. Benefits of chlorophyll:

3.3. The role of chlorophyll in photosynthesis

3.4. Other pigments and photosynthesis

3.5. Chlorophyll biosynthesis 4. Why do leaves turn yellow?

5. Is green color related to photosynthesis?

6. Plants without green leaves

6.1. Seaweed

6.2. Begonias

6.3. Amaranth plant

6.4. Red maple


1. Why are leaves green?

Why are leaves green? Leaves are green because the leaves have organelles called chloroplasts. Chloroplasts contain chlorophyll that helps with photosynthesis. In fact, there are other substances in the leaves that are yellow, orange and red, but because of the secondary proportions, the green color of chlorophyll is still dominant.


However, to answer in a little more detail "Why are leaves green", we can simply understand that: Leaves are green because the cells of the leaves contain many chloroplasts. Each millimeter of leaf contains up to forty thousand chloroplasts. These chloroplasts contain a substance called chlorophyll, the green substance of the leaves. In addition to chlorophyll, leaves contain many other substances. They are orange, red, purple, yellow, etc. However, chlorophyll accounts for the largest percentage.

Green leaves

2. Why is chlorophyll green?

So to know why chlorophyll is green, we need to learn more about spectral physics. The colors that the human eye can see are the colors of substances and objects that cannot be absorbed by the bonded body.


The white light contained in the emitted rays of the sun has seven primary colors. These colors are most clearly distinguished by the naked eye when seeing a rainbow after rain, including: red, orange, yellow, green, blue, indigo, purple. The reason chlorophyll is green is because it absorbs light of other colors, especially red and blue-violet rays. In contrast, chlorophyll does not absorb green light. So green is reflected back to our eyes, so we see green leaves.


Regarding the name, in the Sino-Vietnamese dictionary, "diep" means "leaf", "green" means "green". Just hearing the name, we can already imagine the color of the leaves.


In the case that we shine the chlorophyll of a plant leaf with a red light source, this substance will pick up the red rays, but since there is no green light to reflect back, the result we look at the leaf plants only see a black color… So the green leaves are due to the chlorophyll in the leaves.

Green leaves

3. Chlorophyll

3.1. What is chlorophyll?

Chlorophyll is a green photosynthetic pigment found in plants, algae, and cyanobacteria. In addition to chlorophyll, carotenoids and xanthophylls are also photosensitive pigments found in plants and some other photosynthetic organisms. These pigments are fixed in the chloroplast membrane of the chloroplast.


Chlorophyll absorbs blue and red light most strongly, but poorly in the green part of the electromagnetic spectrum, so the color of chlorophyll-containing tissues is the same as that of leaves.


3.2. Benefits of chlorophyll:

For human health: Chlorophyll is one of the main sources of food and their energy is very good for health. Chlorophyll protects the body in many ways from cleansing the body of heavy metals and toxins to fighting infection.


3.3. The role of chlorophyll in photosynthesis

The overall balanced equation for photosynthesis is:

6CO2 + 6 H2O → C6H12O6 + 6O2

where carbon dioxide and water react to produce glucose and oxygen. However, the overall reaction does not indicate the complexity of the chemical reactions or the molecules involved.


Plants and other photosynthetic organisms use chlorophyll to absorb light (usually solar energy) and convert it into chemical energy. Chlorophyll strongly absorbs blue light and some red light. It poorly absorbs green (reflects it), which is why leaves and chlorophyll-rich algae appear green.


3.4. Other pigments and photosynthesis

Chlorophyll is the most widely recognized molecule used to gather light for photosynthesis, but it is not the only pigment serving this function. Chlorophyll belongs to a larger class of molecules called anthocyanins. Some anthocyanins work together with chlorophyll, while others absorb light independently or at another point in the organism's life cycle.


3.5. Chlorophyll biosynthesis

Plants make chlorophyll from the molecules glycine and succinyl-CoA. There is an intermediate molecule called protochlorophyllide, which is converted to chlorophyll. In angiosperms, this chemical reaction is light dependent. These plants will turn pale if they are grown in the dark because they cannot complete the reaction that produces chlorophyll. Algae and non-vascular plants do not need light to synthesize chlorophyll.

4. Why do leaves turn yellow?

Why do leaves turn yellow when each degree falls? What is the reason why the original green leaves turn yellow, even red, creating beautiful and romantic scenes in the autumn day.

yellow leaves
yellow leaves

Green leaves are due to a pigment called chlorophyll. This substance receives sunlight to create energy for the photosynthesis of plants. When summer ends, the amount of time the sun shines during the day is reduced, which makes it impossible for the leaves to continue to photosynthesize in the winter. Due to dry air conditions and lack of sunlight, the plant forms a wall at each leaf to separate the leaf from the plant. It then stops producing chlorophyll because the plant won't need it until next spring. When chlorophyll is gone, yellow and orange pigments have a chance to appear.

When leaves stop producing chlorophyll, which allows plants to capture light and generate energy, leaves change color very quickly to yellow, which comes from pigments called carotinoids. Some scientists think the leaves continue to make carotinoids after the chlorophyll has stopped working, because the yellow color helps them absorb a little more solar energy.


In addition to yellow, some tree species give red leaves, such as the maple tree - the symbol of Canada. This red color comes from anthocyanin pigments, which are a bit more complex than carotinoids. This has to do with the septum at each leaf. When this wall appears, the leaves will fall to conserve energy for the plant. Before the leaves fall, the plant will retain sugar and nutrients from the leaves, this is when anthocyanin pigments appear.


Explaining the fact that leaves turn red, it is explained that anthocyanin pigments act as a shield from sunlight, blocking harmful rays such as UV and avoiding light that is too strong. It also acts as an antifreeze, protecting plant cells from freezing, and as an antioxidant. In addition, red leaves are also a sign of illness and fatigue.


As for why some leaves turn yellow and some turn red, botanists say that plants that grow best in full light are often more colorful, because so in the fall they can live with the protection of yellow carotinoids. Plants that live in the shade or in poor soil often have more sophisticated mechanisms that require more protection, so their leaves produce more anthocyanins and become darker.

5. Is green color related to photosynthesis?

Leaves are green, so is green color related to the plant's photosynthetic function? We already know that leaves are green because the leaves contain chloroplasts. Which in chloroplast contains chlorophyll that helps the photosynthesis process of the plant.


Chlorophyll when photosynthesis will absorb sunlight to create organic products, and the most absorbed light is in the red-red and blue-violet regions. And green color absorbs very little and is reflected back to our eyes, so it makes our eyes see leaves as green.