Question

When the daylight hours are increased, the rate of photosynthesis
A) Increases
B) Decreases
C) Remains unchanged
D) None of the above

Answer 1

Hint: Photosynthesis is the process by which plants prepare their own food in the presence of sunlight and chlorophyll. It takes place in the chloroplast cell of the leaves.

Complete Answer:
- Photosynthesis is a light dependent reaction. It occurs in the chloroplast of the leaves. The chloroplast is activated by light. It is a chemical process in which carbon dioxide and water is converted to organic food and oxygen. The organic food is utilised by the plants for its growth and development.

The factors affecting the rate of photosynthesis are:
1) Light Intensity- Photosynthesis begins with low light intensity and is maximum at noon, that is the brightest part of the day.
2) Wavelength of light- Chlorophyll can absorb light in Red-Blue wavelength. The photosynthesis is maximum at this wavelength.
3) Availability of water- If water available is less, the stomata pores will not open as a result of which the rate of photosynthesis decreases.
4) Duration of light- The rate of photosynthesis is directly proportional to the duration of light. Longer the plant is exposed to sunlight, the higher will be the rate of photosynthesis.

Thus the correct answer is (A). The rate of photosynthesis increases with the increase in daylight hours.

Note: The photosynthesis is a light dependent biochemical reaction. It occurs only under favourable conditions of proper light, temperature, water, carbon dioxide concentration. If any of these are limited, the rate of photosynthesis will be reduced.