Nutrition in Plants - Photosynthesis

Green plants synthesize their food themselves by the process of photosynthesis. Photosynthesis is a biochemical process by which green plants manufacture their own food using carbon dioxide and water as raw materials in the presence of sunlight and chlorophyll. Oxygen is released as a by-product in this process.

Photo: light; synthesis: make

Photosynthesis is the only process by which solar (sun’s) energy is converted into chemical energy. The overall equation of photosynthesis is:

Carbon dioxide + Water → Glucose + Water + Oxygen

6 CO2 + 12 H2O → C6H12O6 + 6 H2O + 6 O2 ↑

Essential Raw Materials for Photosynthesis

Chlorophyll

To carry out photosynthesis, plants require as raw materials, carbon dioxide (CO2), water (H2O), light and chlorophyll. Light gives energy for photosynthesis. Photosynthesis takes place in chloroplasts in the cells of leaves. The green colour of plants is due to chlorophyll. Chlorophyll is in the chloroplasts. It can trap light.

Sunlight

Sunlight is absorbed by chlorophyll as solar energy.

Carbon dioxide and water

Carbon dioxide and water are combined in the chloroplast with the help of a number of enzymes to yield sugar which is converted into starch. Oxygen formed during photosynthesis diffuses out into the atmosphere through the stomata.

 

Mechanism of Photosynthesis

Photosynthesis occurs in two steps: 

  1. the light reaction
  2. the dark reaction

In the light reaction, light is captured by chloroplast. The reaction occurs in the chloroplasts. In the dark reaction glucose is formed. Dark reaction occurs in chloroplasts. The dark reaction and light reaction occur simultaneously.

What happens to the end products of photosynthesis?

Glucose is formed in photosynthesis. It is either used up by the cells or is converted and stored in the form of starch. The other end product oxygen is released into the atmosphere. Energy is released during photosynthesis.

Significance of Photosynthesis

  1. Photosynthesis is responsible for providing food to all living beings.

  2. Carbon dioxide produced during respiration by all living beings is used up during photosynthesis and does not accumulate in the atmosphere.

  3. Oxygen released during photosynthesis is used for respiration by living beings.