Growth and Development of Horticultural Crops (1+1)

Destruction / inactivation of auxin in plant

• Sufficient levels of auxin in plant required for regulation of plant growth are maintained not only by the synthesis of auxin, but also by its destruction or inactivation.
  
• Chief method for the destruction (degradation) of auxin in plant is its oxidation by O₂ in the presence of the enzyme IAA-oxidase or peroxidase. This oxidation involves removal of CO₂ from the carboxylic group of auxin (IAA) and results in the formation of a variety of compounds, but 3-methyl-oxindole is the major end product.
  
• Auxin may be temporarily inactivated in plants by its conversion into its bound form (bound auxin or conjugated auxin) in which auxin is conjugated to a variety of substances such as carbohydrates, amino acides, proteins or inositol etc.
  
• Rapid inactivation of auxin may occur by irradiation with X-rays and gamma rays, Ultra violet light is also known to reduce auxin levels in plants, Inactivation or decomposition of IAA by light has been called as Photo-oxidation/ oxidation by O₂.