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Plant hormone biosysnthesis and function amjad


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This topic covers major plant hormones and their biosynthesis

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Plant hormone biosysnthesis and function amjad

  1. 1. Biosynthesis Of Plant Hormones Submitted To Dr. S.S. Gill Submitted By Mohammad Amjad
  2. 2. CONTENT 1. Introduction 2. Discoveries 3. Where produced or found in plants? 4. Biosynthesis of plant hormones
  3. 3. Introduction:- • Plant Hormones (Phytohormones)- Plant hormones are signal molecules produced within the plant , which is transmits its effects from one part of the plant to another. • Hormones- A compound produced in one area of an organism and has an affect on an another area. • The word hormone is derived from Greek, meaning set in motion.
  4. 4. Where produced or found in plants? 1. Auxin- Embryo of seed, meristem of apical bud, young leaves. 2. Gibberellins- Meristem of apical bud and roots, young leaves, embryo. 3. Cytokinins- Synthesized in roots and transported to other organ. 4. Abscisic acid- Leaves, stems, roots, green fruit. 5. Ethylene- Tissue of ripening fruit, nodes of stems, ageing of leaves and flowers .
  5. 5. AUXINS (Indole 3- acetic acid) •The Phototropism • Growth or movement of a organism toward or away from a source of light.
  6. 6. Charles Darwin- 1881 Peter Boysen- Jensen -1913 Darwin's study of phototropism. Boysen-Jensen showed a chemical messenger was being transported to the rest of the plant.
  7. 7. Frits Warmolt Went -1926 Arpad Paal- 1918 Went discoverd the signal that was transported from the tip to the rest of the plant and named the signal auxin Paal discovered that the chemical signal induced cell growth.
  8. 8. 1. Auxins Biosynthesis • Two major pathway of auxins biosynthesis:- 1. Try- dependent pathway  IPA pathway (Indole 3- pyruvic acid)  TAM pathway (Tryptamine)  IAN pathway (Indole 3- acetonitrile)  IAM pathway (Indole 3- acetamide) 2. Try- independent pathway • In trp- independent IAA biosynthesis, indole 3- glycerol phosphate or indole is the likely precursors.
  9. 9. Function • Cell elongation:- By increasing cell wall extensibility In stems and coleoptiles. • Cell differentiation:- Xylem and Phloem are regulated by auxin concentration. • Regulates development of fruits:- Auxin produces in the endosperm and embryo of developinng seed. • Function in phototropism. • Apical dominance. • Root growth.
  10. 10. 2. Gibberellins 1. Gibberellins were discovered by Eiichi Kurosawa in japan during worked on fungal disease(“Bakanae” or “Foolish Seedling” ) on rice. 2. This disease caused by “Gibberella fujikuroi” . 3. It was first isolated in 1935 byTeijiro Yabuta and Sumuki, from fungal strains (Gibberella fujikuroi) provided by Kurosawa. Yabuta named the isolate as gibberellin.
  11. 11. GIBBERELLIN BIOSYNTHESIS 1. gibberellins are synthesized via the terpenoid pathway. 2. Based on isoprene units: 3. Biosynthesis occur in 3 part of plant- Plastid, E.R., Cytosol
  12. 12. Functions • Stem elongation:- • Flowering and sex determination • Promotes seed and bud germination • Stimulates shoot elongation and leaf growth • Affect root growth and differentiation • Fruit set
  13. 13. 3. CYTOKININ • Cytokinins are adinine derivatives . • Carlos Miller (1955) – first cytokinin isolated from herring sperm, named kinetin. • Carlos Miller and Letham (1961) – first naturally occurring cytokinin found in plants, later called zeatin.
  14. 14. FUNCTIONS • Cell division • Morphogenesis • Apical dominance • Chloroplast muturation • Cell differentiation • Leaf senescence
  15. 15. ABSCISIC ACID • ABA plays the role of strees hormone. • Identified by Fredrick T. Addicott during studying on abscission of cotton fruits. • The discovery of ABA based on two different physiological function:- 1960 • 1. “abscisin “ cousing abscision of fruits • 2. “dormin” including the dormancy of bud • In 1965 abscisin and dormin are same substance and then term arise name abscisic acid.
  16. 16. The pathway of ABA synthesis beginning with zeaxanthin.
  17. 17. Functions • Roots and shoots growth • Dormancy and germination • Induces seeds to synthesize storage proteins. • Inhibits shoot growth. • Vivipary • Hydrolytic conductivity • NCED- 9-cis-epoxycarotenoid dioxygenase • SDR - short-chain dehydrogenase/reductase
  18. 18. ETHYLENE (gaseous hormone) 19th century – Tree defoliation- coal gas streetlamps – Ethylene - active component of coal gas 1910 – Herbert Henry Cousins - discharge of ethylene in store 1934 – R. Gane - natural product of plant metabolism
  19. 19. – Ethylene is the simplest known olefin (its molecular weight is 28), and it is lighter than air under physiological conditions – It is flammable and readily undergoes oxidation. – Ethylene can be oxidized to ethylene oxide: – and ethylene oxide can be hydrolyzed to ethylene glycol: – In most plant tissues, ethylene can be completely oxidized to CO2 Ethylene Ethylene oxide Oxalic acid
  20. 20.    CO2 (p. 572) Absorbent: alkaline KMnO4 GACC, 1-(-L-glutamylamino) cyclopropane-1-carboxylic acid Exogenous ACC, ethephon (p. 584) Major: Minor:
  21. 21. Functions • Promotes the ripening of some fruits:- the enzymatic breakdown of the cell wall; starch hydrolysis; sugar accumulation; organic acids and phenolic compounds (tannins) disappear; chlorophyll loss and anthocyanins and carotenoids accumulation; aroma and flavor components produced; drying for some fruits. • Leaf epinasty:- The downward bending of a leaf or other plant part • Abscission • Rooting • Fruit ripening • maintains the hooks of dark-growing seedling