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Plant growth regulators Cyto-ABA-Ethy.pptx
- 2. Discovery of Cytokinins Kinetin discovered : Skoog and Miller (1950) from Tobacco pith callus Chemical substance identified as --- 6-furfuryl aminopurine Specific effect on cytokenesis ( cell division) So called "cytokinins" because they stimulate cell division Term cytokinin proposed by Letham (1963) Fairley and Kingour (1966) used the term phytokinins bcoz of plant origin
- 3. Cytokinins can be extracted from: Coconut milk Tomato juice Flowers and Fruits Seven well established types of cytokinins have been reported from plants
- 4. Natural and Synthetic Cytokinins Natural: 1. Zeatin 2. Zeatin riboside 3. Isopententyl adenine (2iP) 4. Dihydrozeatin Synthetic 1. Kinetin 2. Benzyl aminopurine (BAP)
- 5. Site of synthesis and Transport Synthesis Root Apex i.e Root tip is important site of its synthesis - Also synthesized in developing seeds Transport Upward in Xylem stream, young leaves, developing fruits & seeds are the site of transport (Receiving points).
- 6. Responses/Role of Cytokinins in plants Stimulate Cell Division Most important biological effect is to induce cell division Counter-acts Apical Dominance External application of cytokinin promotes the growth of lateral buds and hence counteracts the effect of apical dominance
- 7. Dormancy Red light requirement for the germination of lettuce and tobacco seeds can be broken by kinetin treatment Cell enlargement Significant results observed on the leaves of Phaseolus vulgare Flower induction: induce flowering in short day plants (SDP)
- 8. Protein synthesis : -increased rate of protein synthesis is observed Effects on mobilization (Accumulation and Translocation of solutes) -Plants accumulate solutes actively with the help of Cytokinins -Also help in solute translocation in phloem
- 9. DELAY OF SENESCENCE ( Richmand Lang effect) Ageing process in plants breakdown of proteins and Loss of chlorophyll Thus Yellowing of leaves Senescence postponed by several days by Cytokinin Treatment Effect of Cytokinin in delaying the senescence is called as Richmand Lang effect Richmond and Lang working on leaves of xanthium found ability of kinetin to postpone senescence
- 10. MORPHOGENESIS Depends upon Auxin and Cytokinin concentration High Auxin + Low Kinetin = Root growth Low Auxin + High Kinetin= Shoot growth
- 11. Agricultural Uses Induction of Axillary Buds Roses, Chrysanthemum Micropropagation Shoot proliferation in Tissue Culture Cytokinin application is useful for the production of haploid plants through tissue culture. Such plants resulting in homozygous lines can be used for the hybridization programme. In tissue culture appropriate ratios of cytokinins and auxins are used for organ differentiation.
- 12. Control of Fruit shape: Promalin (Banzyl adenine + GA 4+7) used for controlling fruit shape in Delicious apple. Promalin is also used for increasing Lateral Branching in non bearing apple.
- 14. The Chinese may have been the first to observe the effects of ethylene when they noted that burning incense increased fruit ripening In 1864 leaks in gas lights in street lamps were reported to stunt plant growth and defoliate trees In 1901, D. Neljubow realized that his dark- grown pea seedlings were short, fat and negatively gravitropic (the triple response) because of a component in "laboratory air which he subsequently identified as ethylene Discovery of ethylene
- 15. Cousins (1910) first reported that ethylene occurred in plants. R. Gane (1934) clearly established that ethylene is actually a natural product of ripening fruits and is responsible for hastening ripening process.
- 16. C2H4 Gas at room temperature only natural plant hormone exists in gaseous form Bio-Synthesis Methionine (an amino acid) may be the precursor of ethylene Synthesis of ethylene is inhibited by carbon dioxide and requires oxygen. Ethylene bio synthesis exhibit autocatalytic effect i.e as synthesis starts it increses more additional ethylene synthesis itself Made by all parts of the plant Nodes make more ethylene than internodes
- 18. Functions of ethylene Gaseous in form and rapidly diffusing. Gas produced by one plant will affect nearby plants. Fruit ripening. Epinasty downward curvature of leaves. Encourages senescence and abscission. Flowering - Ethylene inhibits flowering in most species, but promotes it in a few plants such as pineapple and mango. Sex Expression - Cucumber buds treated with ethylene become carpellate (female) flowers, whereas those treated with gibberellins become staminate (male) flowers.
- 20. Abscission and senescence: Prevent opening of flowers Petals loose colour in roses orchards. Ethylene treatment promotes the activity of IAA oxidase enzymes thereby reduces the auxin content in leaf. It also promote the activity of enzyme cellulose and hence enhances the dissolution of cell wall & middle lamella in abscission zone cells. Fruit ripening: Climacteric fruits: rise rate of respiration indicate initiation of ripening completed fruit are harvested. Removal of natural produced ethylene delay ripening Immature climetric fruits will ripen if ethylene treatment given with high concentration.
- 22. Flowering : Universally inhibits all phases of flowering viz., initiation of flower primodia, flower development and opening. However, Ethylene application in Pineapple induce synchronized flowering. Sex Expression: In cucurbitaecea cucumber, bottle guard, ridge guard. Application of ethylene totally suppresses the formation of male flower and increase female flower. In dioecious male plant treated with ethylene produce female flower.
- 23. Relation of ethylene to auxin effects: IAA and all synthetic auxins increase ethylene production. increased femaleness (% female flower) in dioecious, all appears to be responses to ethylene rather than that of auxin.
- 24. Agricultural Uses Ethephon - breaks down to form ethylene 1. Fruit Ripening Tomato, Banana, Melon, etc. Pick unripe and firm for shipping Spray in store to "ripen" Color development and softening Field Spray Uniform and synchronous ripening
- 25. 2. Floral Development inducing flowering in pine apple Pineapple Uniform development of inflorescence 3. Sex Expression increase female Female Flowers Curcubits opposite of GA action 4. Degreening of Citrus Oranges, Lemons, Grapefruit Break down Chlorophyll Leaves Carotenoids
- 27. Abscisic acid In the early 1960s, Philip Wareing confirmed that application of a dormin to a bud would induce dormancy. F.T. Addicott (1965) discovered that some substance stimulated abscission of cotton fruit. he named this substance abscisin. Both substance were same and was named as Abscisic acid (ABA)
- 28. Natural Plant Growth Retardant Opposes action of GA and Auxin Synthesis synthesied in plastids Breakdown product of Carotenoids Synthesied in most of the tissues especially in leaves and seed Transport of ABA Xylem, phloem
- 29. Biosynthesis of ABA i) Isoprenoid pathway: Mevalonate Isopentyal pyrophoshate Geranyl pyrophosphate farnesylpyrophosphate ABA ii) Carotenoid pathway Xanthophyll (violaxanthin)
- 30. Physiological Role of ABA 1. It induces stomatal closure and reduce shoot : root ratio. 2. ABA as a possible defense against salt and cold stress. 3. It induce dormancy as increase its level. 4. It induce abscission (Detachment of plant parts) 5. Geotropism in roots The role of ABA in abscission is controversial because (i) Ethylene application is more effective than ABA (ii) ABA causes senescence in the organ that is shed, with parallel increase in ethylene. (iii) Ethylene is considered to be the actual initiator of abscission.
- 31. Responses Drought Resistance causes stomatal closure Also called as STRESS HORMONE: Helping the plants to cope up with the adverse environmental conditions.
- 32. Applications Bud Dormancy: Induces dormancy Senescence: promoted by ABA Abcission: Accelerate leaf abcission Flower initiation: In General ABA induces flowering in SDP and inhibits flowering in LDP Stomatal closure Counter acts GA: Stress Hormone