Vernalization ; It is the treatment of low temperature for reducing vegetative phase and hastening the reproductive phase. It was first discovered by Lysenko.
Vernalisation refers specially to the promotion of flowering by a period of low temperature. For example - Subjecting the growing of a biennial plant to a cold treatment stimulates a subsequent photoperiodic flowering response.
Significance of vernalization :
1. The reproductive phase can be quickened.
2. The yield is increased.
3. The plants become more resistant towards diseases.
4. It prevents precocious reproductive development late in the growing season, and enables the plant to have sufficient time to reach maturity.
Auxin was isolated by F.W. Went from tips of coleoptiles of oat seedling.
Auxins are of two types :
(1) Natural auxins : These are naturally occuring auxins, isolated from plants and are regarded as phytohormones e.g. IAA. NAA etc.
(2) Synthetic auxins : These are synthesized by artificially e.g. IBA 2,4-D etc.