Nutrients and functions cytokinin,ethylene & abscisic acid

Nutrients and functions cytokinin,ethylene & abscisic acid

1. Cytokinin , Ethylene & Abscisic Acid Lecture 20

2. CYTOKININ CELL KINESIS ( Division ) Cell Division Hormone

3. Cytokinin - Kinetin Skoog and Miller KINETIN Cell division Growth Substances Purine compound 6 Furfuryl amino purine Degradation product of DNA

4. 1. Zeatin Immature corn grains Zeatin Crystalline form Most important and active, natural Cytokinin Letham, 1963 Naturally occurring Cytokinins

5. Naturally occurring Cytokinins 2. Coconut milk Liquid endosperm Contain some growth factors Stimulate the growth

6. Synthetic Cytokinins Benzyl Adenine ( BA ) Benzyl Amino Purine ( BAP )

7. SITE OF SYNTHESIS Root and Shoot tips Translocated through Xylem Primarily in Root Tips

8. Biosynthesis Pathway Adenosine Mono Phosphate + IPP IP-AMP All Cytokinins IPT Iso pentenyl transferase Iso pentenyl pyrophosphate

9. Physiological effects / Roles 1. Induce Cell division 2. Induce Cell enlargement 3. Morphogenesis - Useful in Plant Tissue Culture 4. Delay of Senescence 6. Counteraction of Apical dominance 7. Dormancy breaker 5. Enhance Chloroplast development

10. Morphogenesis Depends upon Auxin and Cytokinin concentration High Auxin + Low Kinetin Low Auxin + High Kinetin Root growth Shoot growth Development and growth of different parts of the plant Mostly useful in Plant Tissue Culture

11. Delay of Senescence (Richmond –Lang) Ageing process in plants Loss of chlorophyll Yellowing of leaves Senescence By Cytokinin Treatment Senescence postponed Effect of Cytokinin in delaying the senescence is called as ‘Richmond Lang effect’

12. Tobacco and lettuce show poor germination in dark They germinate only after an exposure of light CK treated Tobacco seeds Light requirement is alleviated by Cytokinin Germinate in dark

13. Cytokinin – Induced Nutrient Mobilization Transport of many solutes from older part to CK treated zone Transport of Nutrients and Amino acids to site of CK application Enhancing sink efficiency – Increasing partition coefficient

14. Apical Bud Lateral Bud Cytokinin treatment Growth of Lateral buds Apical Dominance Counteraction of Apical Dominance

15. Ethylene

16. ‘Ripening Hormone’ Ethylene

17. 1. Unsaturated Hydrocarbon 2. Only gaseous hormone in plant system 4. Primarily produced in Fruits 5. Plucking, Cutting and Injury of Plant parts Increases the Ethylene production 6. Inhibit the stem Elongation 7. Acceleration of Abscission 3. Highly Volatile Substance

18. BIO SYNTHESIS -- ETHYLENE Methionine Adenosyl Methionine ACC Ethylene ACC Synthase ACC Oxidase O 2 Amino Cyclopropane Carboxylic acid

19. Wounding Chilling Water stress Pathogens Enhances the activity of ACC Synthase More Ethylene production

20. Physiological roles of Ethylene Flowering Sex expression Fruit Ripening Abscission & Senescence Triple Responses Leaf Epinasty Latex flow

21. Physiological roles of Ethylene 1. Promotion of Flowering in Pineapple 2. Induction of Femaleness in Cucurbits 3. Ethylene enhances abscission and senescence Ethylene promotes Abscission and Senescence

22. 4. Responsible for Fruit ripening Increases the cell Respiration Increases the cell Permeability Improves colour & Quality Climacteric Fruits are well respond to Ethylene Non Climacteric Fruits do not respond well to Ethylene

23. 5. Breaks the Dormancy – Stimulate seed germination 6. Induce root formation and cause apical dominance through auxin 7. Increases latex flow in rubber

24. 8. Triple Responses 1. Inhibition of Stem Elongation 2 . Stimulation of Radial swelling of Stem 3.Horizontal growth of stems with respect to gravity Dwarfing  

25. 9. Leaf Epinasty Migration of Auxin to upper side of the petiole More Auxin in upper side More cell elongation in the upper side More growth on upper side Bending Drooping of leaf Bending of leaves

26. Ethylene Compounds 1. Commercial form of Ethylene Ethephon or Ethrel ( 2 – Chloro ethyl Phosphonic acid ) 2. Acetylene and Propylene are also act like Ethylene But ethylene is more effective Ethephon Ethylene Hydrolysis

27. Ethylene biosynthesis Inhibitors AVG – Amino ethoxy Vinyl Glycine AOA – Amino Oxy Acetic acid Ethylene action Inhibitor STS – Silver Thio Sulphate KMnO 4 Ethylene Absorber

28. Abscisic Acid ‘ Stress Hormone’

29. Isolated substance causes Dormancy of Seeds 1. Cornforth (1964) Called as DORMIN 2. Addicott (1965) Isolated the substance from Cotton Fruit Called as Abscission ІІ Both are same. They were jointly given the name Abscisic acid (ABA)

30. ABSCISIC ACID 1. Terpenoid Compounds - Sesquiterpene 2. Close link to Carotenoids 3. Natural Growth Retarding Hormone 4. Synthesis from Mevalonic Acid and Xanthophyll

31. BIO SYNTHESIS Mevalonic acid Isopentanyl Pyro Phosphate Farnesyl Pyro Phosphate Abscisic Acid 1. From Mevalonic Acid

32. 2. From Carotenoids Vialoxanthin Xanthoxin ABA aldehydes ABA Oxidation Lipoxygenase Dehydrogenase

33. SITE OF SYNTHESIS Mostly – Chloroplasts of matured Leaves More ABA found in mature Fruits and Seeds Translocated to other parts of plant Through Phloem Matured seeds

34. Physiological Roles of ABA 1. Inhibit seed germination Inhibit the enzymes Amylase, Protease and Peptidase ABA inhibits GA induced enzyme production

35. 2. Inhibit the shoot growth By decreasing water potential 3. Counteraction of Auxins, GA and Cytokinin Specific antagonist to GA – ‘Anti Gibbrellin’ Stimulates root growth under stress

36. 4. ABA inhibits Vivipary Preharvest sprouting – Character of some grain crop – Mature in wet weather Synthesis of GA & Deficit of ABA

37. 5. ABA promotes seed storage & Desiccation tolerance Maturing seeds – Lose water – Can damage membrane Embryo accumulates sugars & proteins (LEA) High viscous – protect membrane – Desiccation tolerance ABA promotes synthesis of LEA proteins

38. 6. Induce Dormancy of Seeds and Buds Maintains the quality of Potato by inhibit sprouting Sprouting makes potato sweet Embryo dormancy High ABA Low GA Ratio of ABA to GA

39. 7. Accelerates Senescence & Abscission of Leaf, Flowers and Fruits Principle hormone responsible for senescence – ABA Principle hormone reason for abscission - Ethylene

40. 8. Favours Stomatal closure Reduce the TPN rate Regarded as good ‘Anti Transpirant’

41. Thanks Lot