Explain the process of ‘photosynthesis’ in plants

Explain the process of ‘photosynthesis’ in plants. List four factors which influence this process and describe how each of them affects the rate of the photosynthesis process.

Photosynthesis: It is defined as “the process by which plant cells prepare food (carbohydrates) from inorganic raw materials like carbon dioxide (CO2) and water in (H2O) in presence of sunlight and chlorophyll.”


The photosynthesis occurs in 2 phases:

  • Light reaction
  • Dark reaction.

Light Reaction: It needs light that is absorbed by chlorophyll molecules to split water (H2O) molecules into hydrogen and oxygen. The ATP and NADPH9 are produced during it. It takes place in thylakoid membrane of chloroplasts of cell.

Dark reaction: This does not need light energy. It takes place in stroma of the chloroplasts. The ATP and NADPH2 formed during light reaction are utilised and CO2 is reduced to synthesize carbohydrates.

The Four Affecting Rate of Photosynthesis:

  1. Sunlight: It provides energy needed for preparation of food by plants. In absence of sunlight, the photosynthesis does not occur.

  2. Carbon dioxide: C09 acts as substrate for photosynthesis. In it, carbon dioxide and water are converted into carbohydrates.

  3. Water: During photosynthesis, the water is photolysed into oxygen and hydrogen. This provides energy for photosynthesis.

  4. Chlorophyll: The chlorophyll is green pigment. It occurs in leaves that absorbs sunlight.