Page 8 - lesson notes-Plant Growth& Movement

Photoperiodism- the effect of photoperiods or day duration of light hours on the growth and

development of plant, especially flowering is called Photoperiodism. On the basis of

photoperiodic response, flowering plants have been divided into the following categories-

1. Short Day Plants- they flower when photoperiod is below a critical period (continuous
duration of light which must not be exceeded in short day plants and should always be

exceeded in long day plants in order to bring them flower). Example- Xanthium, Rice,

Sugarcane, Potato etc.
2. Long Day Plants- these plants flower when they receive long photoperiod of light,

greater than critical period. Example- Radish, Barley, Lettuce.

3. Day Neutral Plants – the plant can blossom throughout the year. Example- Bean, Wild

Kidney.

Vernalisation- is the process of shortening of the juvenile or vegetative phase and hastening

of flowering by cold treatment. The stimulus of Vernalisation is perceived by meristematic

cells.

Vernalisation helps in shortening of vegetative period of plant and brings about early
flowering.

It is applicable to temperate plants like Wheat, Rice, Millets, etc.

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