Question

What do you understand by photoperiodism and vernalisation? Describe their significance.

Answer 1

Hint: Plants respond to their environment differently based on different periods of the day and temperature. Different plants require different periods of daylight for flowering. Some plants are also dependent on temperature changes for flowering.

Complete answer:
The response of a plant to the duration of daylight or the periods of day and night is known as photoperiodism. Based on their response to the duration of light, different plants may be classified as short-day plants, long-day plants, or day-neutral plants.
Vernalisation is the phenomenon of cold-induced flowering in plants. In plants like the winter varieties of wheat and rye and some biennials like carrot and cabbage, for flowering, exposure to low temperature is necessary. The winter varieties of crops like rye and wheat are planted in autumn and they remain in the seedling stage through the winters and flowers during the summers.
However, if these varieties of crops are sown in spring, flowering is not seen.
It is believed that the hormone responsible for flowering, hypothetically named as florigen is formed in the leaves, and subsequently migrates to the shoot apices, modifying them into flowering apices. Photoperiodism is the process that helps in studying the response of flowering in different plants with respect to the duration of exposure to light.

Note: -Short-day plants are the plants that flower when they are exposed to light for periods less than the critical period, for example-Chrysanthemum. Since they require daytime less than the critical period, they are also known as long-night plants.
-Long-day plants flower only when they are exposed to light for more than the critical period, for example-radish. They are also known as short-night plants.
-When there is no marked correlation between the duration of exposure to light and the flowering, the plants are called day-neutral plants. Example-Tomato.