Question

Given figure shows the effect of interruption of skotoperiod (dark period) in a short day plant by light of different types.

Select the correct option for (i), (ii) and (iii).

	(i)	(ii)	(iii)
(a)$\,\,$	Flowering$\,\,$	Flowering$\,\,$	No Flowering
(b)$\,\,$	No Flowering$\,\,$	No Flowering$\,\,$	Flowering
(c)$\,\,$	No Flowering$\,\,$	Flowering$\,\,$	No Flowering
(d)$\,\,$	Flowering$\,\,$	No Flowering$\,\,$	No Flowering

• A. a
• B. b
• C. c
• D. d

Answer 1

Answer: (C)

Short day plants (or long night plants) require a continuous critical dark period, which must be exceeded for flowering. If the plant is exposed to even a flash of light (red, usually $660\, nm)$ before achieving a critical dark period, flowering is prevented. However, red light effect can be prevented by immediately providing far-red light. Red and farred exposure given in succession show that plant response is determined by the last exposure. Photoperiodic response is believed to be mediated by phytochrome pigment which shows reversible change at red $(660\, nm)$ and far-red $(730\, nm)$ wavelength.