The site of perception of light in plants during photoperiodism is

Concept:

• Photoperiodism is defined as the responses related to the lengths of dark and light periods.
• The hormone florigen, which is responsible for flowering, induces flowering as it migrates from leaves to shoot apices on induction of required photoperiods.
• Photoperiodism helps in studying the response of flowering in various crop plants with respect to the duration of exposure to light.

Explanation:

Option 1: 

• The site of perception of light in plants during photoperiodism is the leaf.
• The developmental responses of the plants to the relative lengths of the light and the dark periods are called photoperiodism.
• During the process of flowering, the photoperiodic stimulus is grasped by the leaves of the plants, and due to this, a floral hormone, florigen is produced in the leaves.

• This hormone is translocated to the apical tip, subsequently causing the initiation of floral primordial.

• Plants have been classified into three groups according to the photoperiods: the short-day plants, the long-day plants, and the day-neutral plants.

• Therefore the correct answer is option 1.

   

• The site of perception of low-temperature stimulus during vernalization is the shoot apex and embryo.

• Therefore this is the incorrect answer.

​Option 3: 

• Stems are not sites of perception of photoperiodism. 

• Therefore this is the incorrect answer.

​Option 4: 

• Axillary buds are not sites of perception of photoperiodism. 
• Axillary buds have the potential to form shoots and may be specialized in producing either the vegetative shoots or the reproductive shoots.

• Therefore this is the incorrect answer.