Why are plants green?

The answer to why are plants green is because of the primary green pigment called chlorophyll and the function of chlorophyll is to help in photosynthesis. Plants are among those organisms that can convert the light energy of the sun into chemical energy. That is why these green plants are called the producers of the ecosystem. The green color of the plant is contributed by the pigment chlorophyll that is present in the chloroplasts. Chlorophyll is not only responsible for the green color of a plant but is also an essential facilitator of photosynthesis. In this article, we will study why are plants green, the functions of chlorophyll, chloroplasts, etc.,

Why are Plants Green?

Plants appear green in color due to the presence of the green pigment chlorophyll. Chlorophyll resides inside the chloroplast and absorbs light energy from the sun. It can absorb colors of light, particularly in the blue and red parts of the electromagnetic spectrum but it reflects or transmits green light, giving plants their characteristic green color. Chlorophyll is crucial to plants as it enables them to absorb the light energy of the sun and drive photosynthesis, the process by which plants use carbon dioxide, and water to synthesize their food in the form of glucose. This makes plants the producers of the ecosystem.

What is Chlorophyll?

The word chlorophyll originated from the Greek words khloros (green) and phyllon (leaves). Chlorophyll is a green pigment found in the chloroplasts of plant cells, as well as in the cells of algae and some other unicellular organisms like cyanobacteria and euglena.

• Chlorophyll serves as a photoreceptor. It is a pigment that helps with photosynthesis by absorbing light energy and use it in splitting up the water molecules that triggers further reaction. Chlorophyll absorbs only red and blue light while green light is not absorbed but reflected. This makes the leaves of the plants appear green.
• There are various types of chlorophyll pigments. These pigments are further distinguished according to their composition, functions, and other kind of characteristics. The chloroplasts are the organelles found in plant cells, that contain chlorophyll.

Chlorophyll Structure

• Chlorophyll contains a porphyrin ring. Within the center of the porphyrin ring, there is a single magnesium ion (Mg²⁺) that is coordinated by four nitrogen atoms from the pyrrole rings. This interaction gives the chlorophyll molecule its characteristic green color.
• Attached to the porphyrin ring is a long hydrocarbon tail known as the phytol tail. This tail consists of 20 carbon atoms and helps anchor the chlorophyll molecule into the thylakoid membrane within the chloroplast.
• Chlorophyll molecules also have side chains attached to the porphyrin ring, which can vary depending on the type of chlorophyll. These side chains may include methyl, vinyl, and aldehyde groups, among others.

Types of Chlorophyll in Plants

There are several types of chlorophyll like chlorophyll a, chlorophyll b, chlorophyll c, chlorophyll d, chlorophyll f, etc. found in plants and other photosynthetic organisms. The most common ones found in plants are chlorophyll a and chlorophyll b.

Chlorophyll a

Chlorophyll-a is the primary pigment involved in photosynthesis. It absorbs light most efficiently in the blue and red regions of the electromagnetic spectrum. It differs from chlorophyll b in structure of side chain.

Chlorophyll b

Chlorophyll-b acts as an accessory pigment in photosynthesis. It absorbs light energy and transfers it to chlorophyll-a, expanding the range of light wavelengths that can be utilized for photosynthesis. Chlorophyll-b is particularly efficient at absorbing light in the blue and orange regions of the spectrum.

Chloroplasts

A chloroplast is a kind of plastid having a double membrane that is helpful in the production and storage of food. It is found in the cells of plants as well as several protists, including cyanobacteria and algae. It is located in the mesophyll cells of the plants and its shape is oval or biconvex.

The chloroplast’s dimensions typically range from 1-3 µm in thickness to 4-6 µm in diameter. These are organelles with two membranes, an inner membrane, and an outer membrane. The organelles called chloroplasts contain chlorophyll which is responsible for converting light energy into chemical energy in the form of glucose so that cells may use it.

Chloroplast Structure

A chloroplast consists of two distinct components called the grana and the stroma.

Grana

Stacks of disc-shaped structures called thylakoids or lamellae comprise grana. The functional units of chloroplasts are called grana, and they are made of pigments called chlorophyll. It is responsible for converting light energy into chemical energy.

Stroma

The homogenous matrix is called the stroma. It surrounds the grana and is comparable to the cytoplasm of cells, containing different kinds of organelles. A variety of enzymes, DNA, ribosomes, and other materials are also present in the stroma. Stroma lamellae serve as links between grana or thylakoid sac stacks.

Membrane envelope

Chloroplasts consist of lipid bilayer membranes on the inside and outside. The stroma is separated from the intermembrane space through the inner membrane.

Intermembrane space

The area between the outer and inner membranes is the intermembrane space. It helps in the transport of ions, metabolites, etc between inner and outer membranes.

Thylakoids (Lamellae)

Within the stroma, the thylakoids are present. Thylakoids are the site for the light-dependent reactions of photosynthesis. Thylakoids are grouped into stacks called grana, with 10–20 thylakoids in each granum. The green color pigment known as chlorophyll is present in the membranes of thylakoids.

Photosynthesis as the Primary Function of Plant Pigments

Plant pigments are specialized molecules that absorb light energy, which is then converted into chemical energy through the process of photosynthesis. However, Chlorophyll is the primary pigment responsible for capturing light energy and initiating the photosynthetic process in plants.

Chlorophyll initiates photosynthesis by absorbing light energy, which excites electrons within its molecules. These excited electrons are passed through an electron transport chain in the thylakoid membrane. This transport of electron results in generation of ATP and NADPH while splitting water into oxygen and protons. The ATP and NADPH produced are used in the Calvin cycle to convert carbon dioxide into glucose.

Why are Some Plants not Green?

Plants contain various pigments other than chlorophyll, which gives them colors other than green. Some examples of plants that have colors other than green are listed below.

1. Coleus (Plectranthus scutellarioides): Leaves of Coleus have variegated patterns of green, red, pink, purple, and yellow. These color variations are due to the presence of anthocyanins and chlorophyll.
2. Japanese Maple (Acer palmatum): Leaves of Maple exhibit colors like red, orange , and yellow. These Colors are contributed by anthocyanins present in their leaves.
3. Croton (Codiaeum variegatum): Similar to Coleus, Croton also exhibits variegated paterns on their leaves contributed by uneven distribution of chlorophyll and anthocyanins in their leaves.
4. Purple Cabbage (Brassica olereaceae): As the name suggest, purple cabbage has purple leaves. The color of its leaves are due to the presence of anthocyanins that accumulate in its leaves.

There are more plants which exhibit different colors like, Rheo, Begonia, Red leaved banana, Black grass, etc.

Conclusion: Why are Plants Green?

The colour of the plants come from a green pigment known as chlorophyll. The functions of chlorophyll is to act as a photoreceptor and is found in an organelle known as chloroplasts. Chlorophyll absorbs the light energy of red and blue wavelengths. Conversely, green light is reflected and not absorbed. This makes plants appear to be green. Chlorophyll, the most significant and abundant pigment in plants, is essential for the biological process of photosynthesis as it converts light energy into chemical energy.

FAQs on Why are plants green?

Why are Plants Green in Colour Class 7?

Chlorophyll, the primary green pigment found in plants and cyanobacteria, is responsible for the vibrant green color of leaves and stems, playing a central role in photosynthesis.

What Gives a Green Color Appearance to the Plants?

The green color appearance of plants is primarily due to the presence of chlorophyll, a pigment involved in photosynthesis.

What is Photosynthesis?

Photosynthesis is the process through which green plants, algae, etc prepare their food making use of carbon dioxide and water in the presence of sunlight. This process forms glucose and releases oxygen.

Which Pigments are Used in Photosynthetic Processes?

There are different kinds of chlorophyll pigments. Chlorophyll a and b are regarded as the principal photosynthetic pigments found in plants.

How are Chloroplasts Different from Chlorophyll?

The green pigment found in all plants, algae, etc. is called chlorophyll. The chloroplasts are the cell organelles that are important to plant cells and are crucial for the process of photosynthesis.

Describe the Structure of Chlorophyll in Brief.

Chlorophyll is made up of porphyrin. The magnesium atom is present in the center of the structure of chlorophyll surrounding four nitrogen atoms. The four carbon atoms and four nitrogen atoms together form the pyrrole ring structure.

Why are Green Plants called Producers?

Green plants harness sunlight and atmospheric carbon dioxide to synthesize carbohydrates through the process of photosynthesis. As they produce their own food, plants are categorized as primary producers in ecosystems.

How many Types of Chlorophyll Pigments are there?

Plants have five types of chlorophyll: chlorophyll a, b, c, d, and e. Each plays a specific role in capturing different light wavelengths, and help in the process of photosynthesis.