The site of perception of light in plants during photoperiodism is :

The correct option is Leaf.

Explanation:
Photoperiodism is the developmental response of plants to the relative lengths of light (day) and dark (night) periods. This response determines when a plant transitions from vegetative growth to flowering.
While the developmental changes and flowering occur at the shoot apex (meristem), the shoot apex itself is not the site that senses the light stimulus.

Scientific experiments have shown that the site of perception of the photoperiodic light stimulus is the leaf. When the leaves are exposed to the inductive photoperiod, a flowering hormone-like signal (florigen) is synthesized in the leaves and translocated to the shoot apex via the phloem, where it initiates floral development.