Plant hormones or growth regulators
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This document provides an overview of plant hormones or phytohormones. It defines phytohormones as organic compounds synthesized in one part of the plant and translocated to another part. The document then classifies the main types of plant hormones and describes where they are produced and their key characteristics. It discusses the functions and physiological effects of the major hormone groups - auxins, gibberellins, cytokinins, abscisic acid, ethylene, and brassinosteroids. For each hormone, it covers aspects like site of production, transport, mode of action, and commercial uses.
Plant hormones or growth regulators
- 1. PHYTOHORMONES SEMESTER VI- BOTANY PLANT PHYSIOLOGY PAPER VI P.HARITHA DL BOTANY TTWRDC (M) SANGAREDDY
- 2. What do you observe and infer???
- 4. What are Plant Hormones? What are different types of hormones and where are they produced in plant?
- 5. Plant hormones are “Organic compounds synthesized in one part of the plant and translocated to another part”. Plant hormones are also termed as - Phytohormones - Plant growth bio regulators - Growth substances
- 6. Endogenously produced In less concentrations Highly diffusible Specific in function May be stimulatory or inhibitory in function Characteristics of Growth substances
- 7. Classification of growth substances Auxins Cytokinin Abscisic acid Gibberellins Ethylene Brassino- steroids
- 8. Classes of Plant growth regulators :It is accepted that there are two major classes of plant hormones: Auxins Cytokinin Gibberellins Brassinosteroids Promoters Ethylene ABA Inhibitors
- 10. Key features of each Growth substance Isolation Structure Mode of action Physiological aspects
- 11. Auxins F.W.Went was first to isolate Auxins from Avena, Wheat and Maize. Thimman defined Auxin as “ an organic substance which at low concentration promote growth along longitudinal axis”. Auxins occur in all groups of plants. Auxin is made in actively growing tissue which includes young leaves, fruits, and especially the shoot apex, legume root nodules, germinating pollen grains Made in cytosol of cells Transport of auxins is polar through phloem & parenchyma by active transport. Chemically Auxins are Indole 3 Acetic Acid (IAA) The Chemical formula: C10H9NO2 Molar mass: 175.187 g·mol−1y An Auxin is made of 1. Indole ring 2. a carboxyl group and 3. at least 1 carbon atom between ring and carboxyl group
- 12. Natural auxins Indole Acetaldehyde Indole Ethanol Indole Aceto Nitrate These get oxidized to IAA by various plant enzymes Synthetic Auxins Naphthalene Acetic Acid (NAA) Indole Butyric Acid (IBA) 2,4,Dichloro Phenoxy Acetic Acid (2,4- D) 2,4,5,Trichloro Phenoxy Acetic Acid (2,4,5- T) 2 Methyl 4 Chloro Phenoxy Acetic acid) (MCPA) Indole 3 Propionic Acid (IPA)IBA & IPA – used as Rooting hormones 2,4,D & 2,4,5-T used as selective herbicides NAA- used in horticulture practices
- 13. Cell enlargement Cell division Apical cell dominance and inhibition of lateral buds Root formation Tropisms Flower formation parthenocarpy Abscission of leaves and fruits Weed killers Sex expression Physiological effects of Auxins
- 15. Mode of action DNA replication, transcription and translation Through ARC complex – RNA synthesis Loosening of cell wall Nucleic acid synthesis
- 16. AUXINS IN AGRI AND HORTICULTURE Treating stem cuttings and scions for vegetative propagation. control of flowering Prevents sprouting of buds Defoliation of plants Prevent leaf fall Thinning of compact fruits Weedicide Development of parthenocarpic fruits Increasing fruit set Prevention of premature fruit drop
- 17. Gibberllins Gibberellins are 4 or 5 ringed diterpenoids which is made of gibbane carbon skeleton. Synthesis of gibberellins is by Mevalonic acid pathway along with terpenes, sterols and carotenoids. Formula: C19H22O6 Molar mass: 346.37 g/mol Discovered by Kurosawa in Rice which was affected by ‘Bakane’ disease caused by fungus Gibberella fujikuroi They are found in all parts of plant but abundant in seeds and young leaves. 50 kinds of Gibberellins are isolated till now, out of which GA1 & GA 3-9 common in all plants Where as GA2 found only in fungus. Movement of gibberellins is non polar By diffusion it moves through xylem and phloem
- 18. PHYSIOLOGICAL EFFECTS OF GIBBERELLINS Effect on dwarf mutants Bolting and flowering Substituting cold treatment Breaking of dormancy parthenocarpy Increase in size of leaves, flowers and fruits Seed germination Flowering and sex expression
- 21. COMMERCIAL USES OF GIBBERLLINS GA2, GA3,GA7 used for enhancing Grape cluster and size. Production of seedless grapes Gibberellins enhance α- amylase in barley, which is used in Beer industry. Promote internodal and stalk length, increase in sugar content in Sugar cane. Flower initiation in certain ornamentals like Poinsettia etc. Preharvest spray with gibberellins delays fruit ripening which help in increased storage period during transport of fruits.
- 22. CYTOKININS Cytokinins are 6 furfuryl aminopurine- a derivative of Adenine. Synthesis by t-RNA cytokinin synthesis/ free cytokinin synthesis/ T-DNA related CK synthesis Chemical formula C10H13N5O Molar weight 219.24 g/mol Haberlandt first identified a substance which would trigger cell divisions Miller isolated and named them Kinetin. They occur in all non vascular and vascular plants. Found in apical meristems, developing seeds, roots, fruit and cambial tissues. In few pathogenic bacteria and fungi, influence disease process in host-parasite relationship. Cytokinin occur naturally and synthetic made too Synthesized in young leaves, fruits, seeds, root tips and translocated by xylem and sieve tubes.
- 23. Cell division and morphogenesis Cell enlargement Breaking seed dormancy Counter action of apical dominance effect of enzymes Delay in senescence Resistance to adverse effects Stomatal movements Development of inflorescence/ enhance fruit set and size PHYSIOLOGICAL EFFECTS OF CYTOKININS
- 26. ABSCISIC ACID ABA is a Sesquiterpenoid, it contains an asymetric carbon atom which exists in (+) or (-) entaiomers. 2 CIS-ABA is active naturally occurring ABA. Formula: C15H20O4 Molar mass: 264.32 g/mol Addicot et al discovered ABA. It is a natural growth inhibiting phytohormone. ABA is naturally occurring as well as synthetic in form. ABA & phenolic compounds- natural inhibitor Malic hydrazide, AMO-1618, Morphactin, Chlorocholine chloride- synthetic inhibitors. ABA is found in all plant groups except Liverworts and few algae. In Liverworts ABA is substituted by Lunularic acid.
- 27. ABA as a growth inhibitor controls unending enlargement of internodes of stems, leaves or any part of the plant. From leaves it gets transported to shoot and root tips through xylem & phloem. Movement is Basipetal. ABA is also referred as Anti Auxin/ Anti Gibberellins/ Anti Cytokinin Biosynthesis is by 2 ways- Indirect Xanthophyll cleavage pathway- higher plants Direct pathway – Isoprenoid pathway- Fungi
- 28. PHYSIOLOGICAL EFFECTS OF ABA Growth inhibition Dormancy Abscission Seed development and germination Fruit growth and flowering Senescence Stomatal movements Root geotropism
- 31. ETHYLENE Formula: C2H4 Molar mass: 28.05 g/mol Auxins seem to regulate Ethylene production. Both auxins and ethylene found in similar parts of plant in high concentrations Discovered by Neljuibow A gaseous Phytohormone Found in all plants in traces Produced in more quantities in meristematic and growing regions and nodal parts, specially produced in large quantities in fruits Non polar transport by diffusion Biosynthetic pathway unclear But requires Methionine as a Precursor.
- 32. PHYSIOLOGICAL ASPECTS OF ETHYLENE Abscission Ripening Effect on growth Degreening Senescence Flowering Dormancy
- 35. PRACTICAL APPLICATIONS OF ETHYLENE ETHREL(2-chloroethyl-phosphonic acid) is a synthetic ethylene used commercially It helps in acceleration of fruit ripening- Banana, Apples Induce flowering in Pineapples Cause senescence in Tobacco leaves Prolongs storage life of fruits Regulate fruit or leaf fall in commercial plants at appropriate time
- 36. BRASSIONSTEROIDS Chemically Polyhydroxy steroids and has common 5 α-choleston skeleton and show structural variation in side chain. 2 Biosynthetic pathways-Early C6 and Late C6 oxidation Molecular Formula: C28H48O6 Molecular Weight: 480.7 g/mol Regarded as Sixth group of Plant growth regulators. First identified by Mitchell et al Discovered in Brassica napus and later identified in 44 plants (37 angiosperms, 5 gymnosperms and one each in algae and pteridophyte) Show growth promoting activity Found in very minute quantities Pollen grains and immature seeds have highest concentration of brassinosteroids. Used in improving yield and growth of many vegetable yielding plants.
- 37. PHYSIOLOGICAL EFFECTS OF BRASSIONSTEROIDS Growth Germination Flowering Senescence Stress tolerance to abiotic factors
- 38. Resistance to chilling Eg. Rice Low temperature stress Eg. Maize Tolerance to high temperatures Eg. Wheat DIFFERENT KINDS OF ABIOTIC STRESS COUNTERED BY BRASSIONSTREROIDS Resistance to drought stress Eg. Sugar beet Normal germination of seeds under saline conditions Eg. Eucalyptus Removal of salt stress Eg. Seedlings of Groundnut
- 41. POST GRADUATION ENTRANCE TEST AND HOW TO PREPARE????
- 48. BOOKS TO PREPARE FOR PG ENTRANCE EXAMS
- 49. Thank you Acknowlegdements I would like to give credit to authors and owners whose content I used in the presentation from the open free internet portal