In short day plants (SDP), flowering is induced by
Photoperiod less than 12 hrs
Photoperiod shorter than critical value and un-interrupted long night
Short photoperiod and interrupted long night
Correct answer: (c)
Solution: Short-day plants (also called as long-night plants) flower when the night length is equal to or greater than some critical period. Thus, short-day plants detect the lengthening nights of late summer or fall. There are two kinds of short day plants: qualitative and quantitative. In qualitative short-day plants, flowering occurs only in short days; in quantitative short day plants, flowering is accelerated by short days. The initiation of flowering in short-day plants is not due to the shorter period of day light but to the long, uninterrupted period of darkness. The minimum critical night length varies considerably from one plant species to another but falls between 12 and 14 hours for many. Examples of short-day plants are florists chrysanthemum, cocklebur and poinsettia, which typically flower in late summer or fall.