Photoperiodism: Plant Responses, Flowering, Light Signals

Photoperiodism Definition

Photoperiodism is the biological response of any living thing toward the comparative length of the light periods. It is a fundamental mechanism by which organisms synchronise their growth and development to environmental cycles resulting from seasonal changes. The photoperiodic control in plants mainly regulates flowering and is, therefore, referred to as photoperiodic flowering.

Photoperiodism In Plants

Plants have specialised photoreceptor proteins called phytochromes and cryptochromes which enable them to keep track of the periodic changes in duration of light and darkness. Three broad categories can thus be made based on their response to photoperiod:

Long-Day Plants (LDP)

• Flowering is induced with a longer exposure to light.

• Examples: Radish, Spinach, Sugar beet

Short-Day Plants (SDP)

• Flowering is induced with a shorter exposure to light.

• Examples: Sunflower, Rice, Soybeans, Tobacco

Day-Neutral Plants (DNP)

• Flower irrespective of day length.

• Flowering depends on other factors, such as age or an external stimulus

• Examples: Rose, Tomato, Cucumber

Mechanism of Photoperiodic Flowering

The mechanism of photoperiodic flowering involves the following process:

• Light/dark signal perception by photoreceptors

• Signaling to the leaves

• Synthesis of the floral stimulus florigen

• Transport of florigen to the shoot apical meristem

• The induction of flowering genes and the development of flowers

Photoperiodism In Animal

• In photoperiodism, seasonal changes induce modifications of behaviour and developmental strategies in many animals, especially at higher latitudes.

• Other animals turn on their behaviour according to the season for certain behaviours less obvious than in plants.

• Such animals include seasonally breeding animals, singing birds during longer days, and insects in a dormant state known as diapause.

Significance Of Photoperiodism

• Photoperiodism is therefore a process critical to an organism's very survival and adaptation to its environment.

• This gives plants the ability to flower at the appropriate time of the year so that successful reproduction and seed production occurs.

• In animals also, photoperiodism helps regulate behaviour where it will coincide activities such as migration, hibernation, and reproduction with seasons.

Conclusion:

One such phenomenon that serves to explain how well intricate the relationship between living organisms and their surrounding environment is photoperiodism. Mechanisms and implications of photoperiodism have brought insight into the progression of research in plant biology, agriculture, and animal behaviour studies.

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