Write a short note on vernalisation.

(N/A) There are plants for which flowering is either quantitatively or qualitatively dependent on exposure to low temperature.
This phenomenon is termed vernalisation.
It prevents precocious reproductive development late in the growing season and enables the plant to have sufficient time to reach maturity.
Vernalisation refers specifically to the promotion of flowering by a period of low temperature.
- Some important food plants,such as wheat,barley,and rye,have two kinds of varieties: winter and spring varieties.
The 'spring' varieties are normally planted in the spring and come to flower and produce grain before the end of the growing season.
Winter varieties,however,if planted in spring,would normally fail to flower or produce mature grain within a single growing season.
Hence,they are planted in autumn.
They germinate,and over winter come out as small seedlings,resume growth in the spring,and are harvested usually around mid-summer.
Another example of vernalisation is seen in biennial plants.
Biennials are monocarpic plants that normally flower and die in the second season.
Sugarbeet,cabbages,and carrots are some of the common biennials.
- Subjecting the biennial plant to a cold treatment stimulates a subsequent photoperiodic flowering response.