Name: Vernalisation- an overview
Uploaded: 2019-07-19
Duration: 7 min 50 s
Description: Vernalisation is the phenomenon of cold exposure that provides some plants with the ability to flower in the best season. Let’s learn about these cold memori...

Question

What is photoperiodism ? What do you mean by photoperiodic induction ? How plants are classified on the basis of photoperiodism ?

Accepted Answer

The cycle of day and night controls many physiological processes in plants. The regulation of physiology and development of plants in response to day length is called photoperiodism. A significant process influenced by photoperiodism is flowering. Flowering required a critical day length for every plant. Hence, photoperiodism is the effect of daily duration of light and dark period on the growth and development of the plant. Initiation of flowering is due to some hormone type chemical substances in the maturing leaves formed due to photoperiodic stimulus.

An appropriate photoperiod in 24 hours cycle constitutes one inductive cycle. For flowering, plants may require one or more inductive cycles. Flowering occurs in plants receiving inductive cycles after intervals of unfavourable photoperiods. It is called photoperiodic induction. Increasing the number of inductive cycles results in the early flowering of the plant. The light stimulus is perceived by the help of proteinaceous substances called phytochrome. The site of photoperiodic induction is leaves.

Plants are divided into three categories depending upon the duration of the photoperiod, which are short-day plants, long-day plants, and day-neutral plants.

Short day plants (SDP): These require a relatively short daylight period (about 8 to 10 hours) and a continuous dark period of about 14-16 hours for subsequent flowering. In these plants, the dark period is critical and must be continuous. In a short-day plant, if the dark period is interrupted with brief exposure to red light, the flowering will not occur. Most of the winter flowering plants belong to this category. Examples: Nicotiana tabacum (Tobacco), Glycine max (Soybeans), Solanum tuberosum (potato), etc.

Long day plants (LDP): These require longer daylight (usually 14-16 hours) in a 24 hours cycle for flowering. They need a day length longer than the critical value. These plants are also called short night plants. Long day plants require either a relatively small period of darkness or no darkness at all. Examples: Triticum aestivum, Avena sativa, Saccharum officinarum, etc.

Day neutral plants: They do not require specific day or night period for flowering are called day neutral plants. Interruption of day or night period has no effect on such plants. Examples of day-neutral plants are Cucumis sativus (cucumber) and Helianthus annuus (sunflower), Lycopersicum esculentum (tomato), etc.

What is photoperiodism ? What do you mean by photoperiodic induction ? How plants are classified on the basis of photoperiodism ?

Important Questions on Plant Growth and Development

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