Question

Nicotiana tabacum, a Short Day Plant, when exposed to more than critical period of light fails to flower. Explain.

Answer 1

Photoperiodism:

Flowering in some plants depends on their exposure to light and dark periods. Photoperiodism is the response of plants to the relative length of day and night. These responses are in relation to a critical duration of light exposure (critical photoperiod) which varies from plant to plant.


Classification of plants on basis of photoperiodism:

Plants are classified under three groups according to the photoperiods:

• Long-day plants (LDP): The plants require a photoperiod longer than the critical photoperiod for flowering.
• Short-day plants (SDP): The plants requiring a photoperiod shorter than the critical photoperiod for flowering.
• Day-neutral plants: The plants flower without any correlation to the photoperiod.

Flowering in Nicotiana tabacum:

Nicotiana tabacum is a short-day plant and requires a photoperiod shorter than the critical photoperiod for flowering. When exposed to light for a longer period, it will not flower as its relative requirement for a dark period gets reduced.