State the role of photoperiod in crop production.
Answers
★ PHOTOPERIODISM:-
→ Some plants require a periodic exposure to light to induce flowering. Such plants are able to measure the duration of exposure to light.
→ Based on duration of light required, plants are 3 groups:
o Long day plants: They require the exposure to light for a period exceeding a well defined critical duration.
o Short day plants: They require the exposure to light for a period less than the critical duration before the flowering is initiated in thern.
o Day-neutral plants: They have no correlation between exposure to light duration and induction of flowering response.
→ Like the duration of light period, duration of dark period is also important.
→ The response of plants to periods of day/night is called photoperiodism.
→ While shoot apices modify into flowering apices prior to flowering, they by themselves cannot perceive photoperiods. The site of perception of light/dark duration is the leaves.
→ It has been hypothesised that there is a hormonal substance responsible for flowering. When the plants are exposed to the necessary photoperiod, the hormone migrates from leaves to shoot apices to induce flowering.