Question 5 What do you understand by photoperiodism and vernalisation? Describe their significance.
Class XI Biology Chapter - Plant Growth and Development Page 254
Answers
★Effect of requirement of relative length of day (photoperiod) and night (dark phase) on flowering of plants is called as photoperiodism.
→On the basis of it's responses plants are classified in two catogeries :-
1) Short day plant
2) Long day plant.
→Photoperiodism helps in studying of the various crop plants.
★Concepts of hormone 'vernalin' in vernalisation was given by Melcher.This is actually a hypothetical plant hormone because has not been isolated.
Effect of low temperature on the initiation and development of Flowers is something called vernalisation.
It helps in better and early flowering and shortening the life span of the plant.
Answer:
Photoperiodism can be termed as the response of plants to periods of day/night. It is theorized that the hormonal substance that is responsible for flowering, is formed in the leaves which subsequently migrates to the shoot apices and alters them into flowering apices. This process of photoperiodism helps in studying the response of flowering in different crop plants when the duration of exposure of light is considered.
Vernalisation is the phenomena where the process of flowering in some plants is either quantitatively or qualitatively dependent on the exposure to lower temperatures. In particular, it refers to promoting the flowering process by a period of lower temperatures. The process prevents precocious reproductive development late in the growing season which thereby enables the plant to have sufficient time to attain maturity.