07 Plant Growth and Mineral Nutrition - part 15 - Vernalization

07 Plant Growth and Mineral Nutrition - part 15 - Vernalization


Vernalization (Yarovization) : 
  • Temperature as environmental factor influences several physiological processes including reproduction. 
  • Temperature as a factor has three cardinal points viz -  
  1. Minimum
  2. Optimum and 
  3. Maximum temperature. 
  • It is a low temperature (chilling) treatment that induces early flowering in plants as was evidenced by Klippart (1918). 
  • Chouard (1960) defines vernalization as accelaration of the ability to flower by chilling treatment. 
  • The term vernalization was coined by T.D Lysenko (1928) for the effect of low temperature on flowering in plants. 
  • It is an influence of temperature on development and flowering. 
  • Many plants such as cereals, crucifers require a period of cold treatment for flowering. 
  • It is the method of inducing early flowering in the plants by pretreatment to their seeds/ seedlings at low temperature (1-60C for one to one and half months' duration). 
  • Site of vernalization : Shoot apical meristem.  
  • Generally, vernalization is effective at seed stagein annual plants. 
  • Vernalization stimulus is also a chemical stimulus named as vernalin. This can be transferred through grafting (Melcher 1939). 
  • The reversion of vernalization by high temperature treatment is called devernalization. 
Advantages of vernalization : 
  1. Crops can be produced earlier. 
  2. Crops can be cultivated in regions where they do not grow naturally
Know the Scientist : 
  • The low temperature induces early flowering which was first noticed by Klippart (1957) while working on two varieties of wheat- `winter wheat' and `spring wheat'. 
  • The winter wheat sown in winter, produces flowers in the following summer. 
  • The spring wheat sown in the spring and produces flowers during summer. 
  • However, if winnter variety is sown in spring does not produce flowers during summer but does so in the next year's summer. 
  • Observation : If germinated seeds of `winter wheat' are treated with low temperature, it can behave as spring wheat. 
  • Conclusion : winter wheat requires low - temperature exposure before the onset of flowering. 

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