Question

Analyse the illustration given below and answer the following questions.
(a) Identify the pigment labelled as ‘X’.
(b) Which part of the plant produces this pigment?
(c) How does ‘X’ induce flowering?

Hint:

Phytochrome in leaves detects light duration and helps produce florigen, the hormone responsible for flowering.

Answer 1

Step 1: Understanding the diagram.
The diagram shows a pigment (X) converting into a signal which leads to flowering. This represents the concept of photoperiodism, where light-sensitive pigments control flowering in plants.
Step 2: Identification of pigment ‘X’.
The pigment labelled ‘X’ is Phytochrome. It is a light-sensitive pigment that detects changes in light duration.
Step 3: Site of production.
Phytochrome is produced in the leaves of the plant, which perceive light signals.
Step 4: Mechanism of inducing flowering.
Phytochrome exists in two forms (active and inactive) and responds to light and dark periods. Based on day length, it triggers the production of a flowering hormone (florigen), which acts as a signal.
Step 5: Final effect.
This signal (florigen) is transported to the shoot apex, where it induces flowering in the plant.