Question

Which one of the following is correct for the blooming of short- day plants?
(a) The long dark period is not critical.
(b) It is affected by the interruption of the long dark period by brief exposure of light.
(c) It is not affected by the interruption of the long dark period by brief exposure of light.
(d) It is affected if the continuous light period is interrupted.

Answer 1

Hint: These types of plants require a very little amount or no amount of light and a long period of darkness for the plants to flower. They only flower when the period of night is extended as they grow only in the dark.

Complete answer:
The short- day plants are those plants whose night time is extended more than their critical photoperiod for them to bloom and flower. They cannot bloom when the light is presented even for a light while. So, the exposure of light for a brief time will interrupt the period of darkness leading to the non- flowering of the plants.
- The Physiological process occurring in the plants and the animals according to the period of lightness and darkness.
- The process of development of plants based on the period of light and dark is known as photoperiodism.
- On the basis of photoperiods, plants are divided into three categories:
 Short- day plants
 Long-day plants
 Day- neutral plants
- Long-day plants occur when the night period is less than the critical photoperiod. These plants require larger day lengths and light and lesser dark or night periods to bloom. Example: Pea, Wheat, Braley, etc.
- Short-day plants occur when the night period is larger than the critical photoperiod. These plants require a large night or a large darker period and a smaller light period. The light produced by the moon is natural and very low so they will not interrupt the dark period of the plants. Example: Rice, Cotton, Soybeans, etc.
- Day-neutral plants do not depend upon photoperiodism. Their flowering occurs at a definite stage after their growth period. Example: Cucumbers, tomatoes, roses, etc.
So, the correct answer is ‘It is affected by the interruption of the long dark period by brief exposure of light’.

Note: The changes in photoperiod occur due to the presence of photoreceptors that act as the sensory reec[tors in plants and animals. These photoreceptors include phytochrome and cytochrome. They send signals to the plants as the night r day period changes. The process of photoperiodism was first discovered by Graner and Allard in 1912.