Question

What is the site of perception for photoperiodism induction in plants?

• A. Roots
• B. Leaves
• C. Stem apex
• D. Flowers

Hint:

Leaves perceive day length using phytochrome pigments and send flowering signals (florigen) to the shoot apex.

Answer 1

The Correct Option is B

Concept: Photoperiodism is the physiological response of plants to the relative length of day and night. It plays an important role in controlling processes such as flowering, dormancy, and seasonal growth patterns. Plants measure day length using specialized pigments called phytochromes.

Step 1: Understanding perception of photoperiod.
The perception of day length occurs primarily in the leaves. Leaves contain photoreceptors such as phytochrome that detect changes in light and darkness.

Step 2: Signal transmission.
Once the leaves perceive the appropriate photoperiod, they produce a chemical signal known as florigen. This signal travels from the leaves through the phloem to the shoot apical meristem. \[ \text{Leaves (perception)} \rightarrow \text{Florigen signal} \rightarrow \text{Shoot apex (flower formation)} \]

Step 3: Role of the shoot apex.
Although flowering occurs at the shoot apex, the detection of the photoperiod takes place in the leaves. Therefore, leaves act as the primary site of photoperiodic induction.