Photoperiodism: Meaning, Process and Examples

Photoperiodism is a biological response of plants and animals to change in the proportion of dark and light. Garner and Allard first studied photoperiodism in plants in 1920. “Photo” means light and “period” means the length of time. Plants require light to bloom. The duration when the plant is required to bloom is known as critical photoperiod. Photoperiodism helps to determine the flowering season of different types of plants.

What is Photoperiodism?

Photoperiodism is defined as the response of animals and plants to the relative length of day and night. “Photo” means light and “period” means the length of time. Garner and Allard first studied photoperiodism in plants in 1920. It is the response of plants to the periods of day and night. Plants usually use this time to grow, develop, and reproduce. It is a fascinating process in which shoots modify themselves into flowering apices before flowering.

Role of Phytochromes

Phytochromes are the leaf pigments which are used to initiate photoperiodism in plants. The flowering plants uses the photoreceptor proteins which are usually present in the leaves to detect the period of darkness and light. Phytochromes are of two types: Active form and inactive forms. Active forms predominates during the day whereas the inactive form predominates during the night. In the absence of light the active form of phytochromes reverts to an inactive form.

Photoperiodism in Plants

They have main role in cross-breeding, hybridization experiments and others. Photoperiodism helps to determine the flowering season of different types of plants. Horticulturists uses photoperiodism in plants for obtaining high yields of rhizomes and tubers. It also encourages cross-breeding between the flowers which grows in different seasons. Flowering plants angiosperms shows photoperiodism.

Different types of Plants related to Photoperiodism

Plant require light to bloom. The duration when the plant required to bloom is known as critical photoperiod. Active form of phytochromes determine the critical photoperiod of different types of plant. Following are the types of plants:

• Short Day Plants (SDP): Short day plants requires continuous dark period of 14 to 16 hours for flowering. These plants require less exposure to lights. They bloom when the days are shorter. They are also known as long night plants. For example- tobacco, coffee, soybean and so on.
• Long Day Plants (LDP): Long day plants requires long exposure of light during the dark period. They flowers when the days are longer up to 14 to 16 hours. They are also known as short night plants. Example- spinach, sugarcane, radish and so on.
• Day neutral plants (DNP): These type of plants are neutral to the length of day or night. They don’t require critical photoperiod for flowering. These type of plants are perennial. Example – cucumbers, tomatoes, roses and so on.
• Intermediate plants (IP): These type of plants require definite range of light hours to flower and they do not flower above or below the defined range. Example – wild kidney beans.
• Short-Long day plants (S-LDP): They require shorter photoperiods for initiating flowering and long photoperiods for blossoming. They are long day plants. They flower between spring and summer. Example – rye.
• Long-Short day plants (L-SDP): They require short days to blossom and long photoperiods for floral initiation. They are short day plants and they flower between summer and autumn. Example – bryophyllum.

Photoperiodism in Animals

The animals who are living in the latitudes use photoperiodism to adjust themselves to some development strategies or seasonal behaviour. Photoperiodism in animals is a process in which some animals respond in a particular time of the year. It also affects the color of fur of some animals. For example – singing of birds, seasonal breeding occurs in many animals and so on.

FAQs on Photoperiodism

1. What do you mean by Photoperiodism ?

Answer:

Photoperiodism refers to the response of plants and animals to the relative length of day and night. “Photo” means light and “period” means the length of time.

2. Name the types of Phytochromes ?

Answer:

The two types of phytochromes are:

• Active form
• Inactive form

3. Write the importance of Photoperiodism ?

Answer:

The importance of Photoperiodism is Horticulturists uses photoperiodism in plants for obtaining high yields of rhizomes and tubers. It also encourages cross-breeding between the flowers which grows in different seasons.

4. What is the Significance of Photoperiodism?

Answer:

Floweing plant of different plant is determined by photoperiodism.