Question

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.

Answer 1

The process of photosynthesis occurs in two phases – the   light reactions   and the  dark reactions .

Light reactions –   As the name suggests, this reaction takes place in the presence of light. Light energy is absorbed by chlorophyll molecules and is utilized for splitting water molecules into hydrogen and oxygen. Additionally in this phase, assimilatory power in the form of ATP and NADPH 2  are produced.

Answer 2

Photosynthesis occurs in two phases—light reaction and dark reaction.

Light Reaction:

This phase occurs in the thylakoids of the chloroplast. Various events occurring in

photosynthesis:

 Absorption of light energy

 Splitting of water molecules into hydrogen and oxygen atoms

 Formation of ATP and NADPH2

Dark Reaction:

This phase occurs simultaneously with the light-dependent reaction. In this phase,

carbon dioxide is converted to glucose by using ATP and NADPH produced during

the light reaction.

Factors which affect the rate of photosynthesis:

Light:

 Rate of photosynthesis increases when light gets brighter.

 Rate of photosynthesis increases linearly with increasing light intensity.

Carbon dioxide concentration:

 Increase in the concentration of carbon dioxide increases the rate of

photosynthesis.

 Rate of photosynthesis increases linearly with increasing carbon dioxide

concentration.

 Increased carbon dioxide concentration is beneficial for greenhouse crops

such as tomatoes.

Temperature

 Higher the temperature, greater is the rate of photosynthesis.

 Rate of photosynthesis slows down when the temperature is more than 40°C

because the enzymes involved in the chemical reactions of photosynthesis

are temperature sensitive and are destroyed at higher temperatures.

Water

 Water stress causes leaves to wilt, thereby reducing their surface area and

metabolic activity.