Light plays an important role in the life of all organisms. Name any three physiological processes in plants which are affected by light.

Three physiological processes in plants which are affected by light are:

a) Photosynthesis: The process of photosynthesis occurs when green plants use the light energy to convert carbon dioxide (CO₂) from air and water (H₂O) absorbed from the soil via roots into carbohydrates. Light energy is absorbed by chlorophyll which is a photosynthetic pigment of the plant.

b) Photoperiodism: In photoperiodism, flowering is regulated in response to the day length exposure time or photoperiod. Short Day Plants flower when day length is below a certain threshold level (as in rice), while in long day plants when day length is above a certain threshold level, only then can flowering occur (like in spinach).

Pfr: active form of phytochrome is Pfr or phytochrome far red.

Pr: inactive form of phytochrome is Pr or phytochrome red.

These forms are interconvertible between each other.

c) Phototropism: Phototropism is the growth of plant towards or away from light. Growth towards the light source is called positive phototropism, while away from the light source is called negative phototropism. In phototropism, plant usually bends or grows in response to the light. Shoot usually directs itself towards light while roots away from it.