Why are leaves green?

Leaves are the most crucial parts of a plant because they provide food and air for the plant to grow and stay healthy. They are the primary source of food in plants as the leaves are the site to perform photosynthesis. Photosynthesis is a process by which green plants, in presence of sunlight, take in carbon dioxide and water from the surroundings and synthesizes sugars and nutrients for the plants.

Plant roots may reach deep down to gather water which acts as raw material in the process of photosynthesis. Oxygen is released as the end-product of photosynthesis. This oxygen supports the life of all living organisms on the planet. 


Why are leaves green?

The color of the leaves comes from pigments called chlorophyll. This pigment gives the characteristic green color to the plant. It is the responsibility of the chlorophyll to perform photosynthesis and synthesize food for the plant during the daytime. The foods prepared by the plant are rich in sugar and starch. Now, we can understand how important leaves are for the survival of plants as well as living organisms.

The equation of photosynthesis can be represented as:

Sunlight + Carbon Dioxide + Water —> Sugar(glucose) + Water + Oxygen

What are the different processes performed by plants throughout the day?

Leaves perform various different actions during the day and night. Let’s dive into this topic in detail.

During Daytime:

1. Carbon dioxide in

During the daytime, plants perform photosynthesis. The pigment chlorophyll allows the green leaves to fix carbon dioxide from the surroundings while the plant roots draw water which is then used to perform photosynthesis. Various chemical reactions take place which helps in the generation of food and other by-products.

2. Oxygen out

The process of photosynthesis not only generates food but also releases oxygen into the atmosphere as one of its by-products. This oxygen helps in the survival of all the creatures. Glucose is also synthesized in the process which is stored within the plants for later use.

During Night

Carbon dioxide out

During the night, there is no sunlight to support the process of photosynthesis. As a result of which no food and oxygen are generated during the night. Plants perform respiration during the night where carbon dioxide is released into the surroundings.

Oxygen in

During the night, plants take in oxygen to break down the glucose stored in the plants during the daytime. This breakdown provides energy to the plants to perform different activities.

Losing Water

The surface of leaves has numerous tiny openings, called stomata. They open to act as a medium for the exchange of gases. Water escapes as a gas called water vapor. More water flows to the leaf to replace the water vapor. This keeps up the circulation of the water in the whole plant.


  1. Panda bears eat primarily bamboo leaves (99% of their diet). They consume 12-38 kg of these leaves every day.
  2. The plant with the largest leaves in the world is Raphia, a species of Raffia Palm belonging to the palm tree family.

Objective Questions:

  1. ____ + Carbon Dioxide + Water —> Sugar(glucose) + Water + Oxygen
    Which of the following elements is missing in photosynthesis?
    (a) Sunlight
    (b) Moonlight
    (c) Rain
    (d) Sea Water
  2. Which plant has the largest leaves in the world?
    (a) Cactus
    (b) Raphia
    (c) Spinach
    (d) None of these
  3. Which of the following acts as medium for the exchange of gases?
    (a) Stomata
    (b) Chlorophyll
    (c) Chloroplast
    (d) Carotenoids
  4. Which pigment provides the color to the leaves?
    (a) Stomata
    (b) Chlorophyll
    (c) Chloroplast
    (d) None of these


  1. Plants give out carbon dioxide in night. (T/F)
  2. Oxygen is released as the end-products of photosynthesis. (T/F)
  3. Glucose is not given out as an end-product. (T/F)
  4. Stomata keeps the circulation of water in the plant intact. (T/F)
  5. Leaves can be of any color like red, yellow, blue. (T/F)

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