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Biosynthesis of auxin[1]
This document summarizes information about the plant growth hormone auxin. It defines auxin as chemical substances that promote stem or root growth. The first known auxin is indole-3-acetic acid. There are two types of auxin: natural auxins produced by plants like IAA, and synthetic auxins created in labs. The document then describes the three step biosynthesis process of IAA from the amino acid tryptophan. Finally, it lists several physiological effects of auxins, including cell elongation, promotion of cell division, root growth, apical dominance, prevention of abscission, formation of seedless fruits, and regulation of plant growth movements.
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Biosynthesis of auxin[1]
- 1. Department of biochemistry Presentedby – Rajnish kumar Semester- 02 Roll no -02/16
- 2. Plant growth hormone(Auxin) •The term auxin includes all those chemical substances which promote growth of stem or coleoptile sections • It come as a first plant growth hormone from the work of Darwin (1881). • Naturally occurring auxin is indole-3-acetic acid.
- 3. Types of auxin •1) Natural auxin – these are naturally occurring auxin in plants and therefore regarded as phytohormones. The best known natural auxin is indole-3-acetic acid. • 2) Synthetic auxin – these are many chemicals synthesized in the laboratories that cause various physiological response similar to IAA. Synthetic auxins are not considered as phytohormones
- 4. Biosynthesis of Auxin 1)first of all the amino acid tryptophan donates its amino group to another alpha keto acid by transamination reaction to become indole pyruvic acid. The reaction is catalysed by tryptophan transaminase. 2)Then indolepyruvic acid undergoes decarboxylation in presence of enzyme indole pyruvate decarboxylase to become indole acetaldehyde
- 5. • 3) finallyindole acetaldehyde oxidizes to become indole-3-acetic acid. This reaction is catalysed by enzyme indole acetaldehyde dehydrogenase
- 7. Physiological effects ofauxins • 1) It helps in cell elongation • 2) It helps in promotion of cell division in cambium. • 3) It helps to promote root growth in low concentration. • 4) It influence the apical buds and suppress the growth of lateral buds this is called apical dominance.
- 8. • 5) Ithelps in prevention of abscission layer • 6) It also helps in the formation of seedless fruits without fertilization • 7) Auxin also regulate plant growth movement like phototropism and geotropism.
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