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Lecture 7 Growth and Development

Lecture 7 Growth and Development. Growth Irreversible change in Mass Development Irreversible change in State Embryogenesis Juvenile Adult Vegetative Adult Reproductive. Growth. Components 1. Cell Division 2. Cell Enlargement 3. Cell Differentiation. Cell Division.

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Lecture 7 Growth and Development

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  1. Lecture 7Growth and Development • Growth • Irreversible change in Mass • Development • Irreversible change in State • Embryogenesis • Juvenile • Adult Vegetative • Adult Reproductive

  2. Growth • Components • 1. Cell Division • 2. Cell Enlargement • 3. Cell Differentiation

  3. Cell Division • Meristematic Cells (Stem Cells) • Primary • Shoot Apical Meristem (SAM) • Root Apical Meristem (RAM) • Secondary • Axillary Buds • Vascular Cambium • Cork Cambium • Pericycle (root)

  4. Cell Enlargement • Adjacent to Meristems • Internode growth - Shoot • Zone of Elongation - Root • Turgor Pressure • H2O Uptake • Cell Wall Loosening • new cell walls

  5. Cell Differentiation • Cessation of Cell Enlargement • Secondary cell walls • Xylem - Vascular tissue • Fibers • Epidermal cells • root hairs • leaf hairs • guard cells • Leaves, Flowers • Fruit, Tubers, Bulbs, etc.

  6. Types of Growth • 1. Determinant Terminal shoot apex flowers • 2. Indeterminant Axillary buds flower Terminal buds vegetative • 3. Monocarpic Flower once then die • 4. Polycarpic Flower repeatedly over several seasons

  7. Types of Growth • 5. Annual Monocarpic Flower in one season and then die • 6. Biennial Monocarpic Flower in second season and then die

  8. Types of Growth • 7. Herbaceous Perennial • Polycarpic • Determinant Flower early and then go dormant Flower Bulbs • Indeterminant • Flower throughout season • Shoot dies in Fall

  9. Types of Growth • 8. Woody Perennial • Polycarpic • Indeterminant flower only once per year • Biennial Bearing flower and set fruit every other year • Mast Flowering more prolific in some years than in others

  10. Dormancy • Ecodormancy • Imposed by Environment • Temperature, Daylength, etc. • Paradormancy • Physiological Dormancy • Apical Dominance • Endodormancy • True Dormancy • Seeds, Terminal Buds

  11. PLANT GROWTH REGULATORS • 1. Endogenous • a. Substance produced by a plant that affects the pattern of growth and development. • b. Production by the plant is regulated by the environment. • 2. Exogenous • a. Substance applied to the plant that alters growth and development in the same way that endogenous substances do. • b. May be the same or different chemically from the endogenous substance

  12. PLANT GROWTH REGULATORS • 3. Hormone • a. Substance that acts in very low concentration (micro-molar or less) • b. Produced in one part of plant and act in another (translocatable) • c. Has the same response in many different plant species

  13. PLANT GROWTH REGULATORS • A. Primary • 1. Auxins • 2. Cytokinins • 3. Gibberellins • 4. Abscisic Acid • 5. Ethylene

  14. PLANT GROWTH REGULATORS • B. Secondary - newly discovered • 1. Jasmonic Acid • 2. Brassinosteroids • 3. Juglone • 4. Salicylic Acid • 5. Polyamines

  15. PLANT GROWTH REGULATORS • C. Others - not yet confirmed or understood • 1. Peptide Hormones animals maybe plants • 2. Oligosaccharides cell wall signaling • 3. Phospholipids inositol phosphates, diacylglycerides • 4. mRNA or Protein Florigen (floral induction)

  16. Natural Auxin • 1. Endogenous • Indole Acetic Acid

  17. Auxin Discovery

  18. Auxin Discovery

  19. Auxin Discovery

  20. Synthetic Auxins

  21. Auxin • Synthesis • a. Young developing leaves • b. Terminal buds, growing axillary buds • c. Seeds • Transport • a. Basipetal away from tip • b. Apoplastic outside cells • c. Symplastic through cells and plasmodesmata • d. Phloem – Conjugated Forms - Glycosides

  22. Auxin Action • Mechanism of Action • a. Bind Receptor Protein Plasma membrane • b. Transport into cell • c. Activate ATPase in Plasma membrane • d. H+ ion extrusion • e. acidify cell wall • f. break hemicellulose-pectin bonds • g. cellulose microfibrils slide apart • h. cell enlarges

  23. Auxin Polar Transport

  24. Auxin Cell Wall Loosening

  25. Auxin Responses • Cell Enlargement • Shoot Growth • Internodes • Tubers • Bulbs • Root Growth • Storage Roots • Adventicious Roots • Fruit Growth • Strawberry - Receptacle enlargement • Apical Dominance • Auxin:Cytokinin Ratio • High - Dormant Axillary Buds • Low - Axillary Bud Growth

  26. Auxin Agricultural Uses • Rooting of Cuttings Propagation Greenhouse and Nursery Crops Hormodin, Rootone, etc. Commercial preps of 2,4-D • Herbicide • High Concentration 2,4-D • Dicots more sensitive • Monocots less sensitive • Weed control in cereal crop production • Prevent Abscission of Leaves and Fruit • Older leaves • Ripe Fruit • Endogenous production of IAA stops • Replaced by exogenous NAA

  27. Auxin Agricultural Uses • Chemical Thinning • Differential sensitivity of developing fruit • High Concentration of NAA causes abscission • Induction of Ethylene Synthesis • Tissue Culture Propagation • Auxin:Cytokinin Ratio • High - Roots • Low - Shoots • Equal - Callus

  28. NH2 ATP N DNA N RNA N N NAD(P) (ribose) Adenine (Adenosine) CH3 N-CH2-C=C-CH2-OH N N N N (Ribose) Zeatin (Riboside) Cytokinins • Adenine + Ribose • Adenosine • ATP, ADP, AMP • DNA, RNA • Nucleotides • NAD, NADP, FAD • Cytokinins • Cis & Trans Zeatin • + Ribose • Zeatin Riboside

  29. CYTOKININS (IPA)

  30. Cytokinins • Synthesis • Root Apex • Transport • Upward in Xylem

  31. Cytokinins • Responses • Stimulate Cell Division • Apical Dominance • High Auxin in Shoot Apex • High Cytokinin in Root Apex • Gradient Between: • High Auxin:Cytokinin • Dormant Axillary Buds • Low Auxin:Cytokinin • Branch Growth

  32. Cytokinins • Synthetic Cytokinins • Kinetin DNA degredation • Benzyladenine (BA or 6-Benzyl amino purine) • Agricultural Uses • Limited • Induction of Axillary Buds Roses, Chrysanthemum • Micropropagation Shoot proliferation in Tissue Culture

  33. Gibberellins • Family of more than 70 structures like this • Synthesis • Fungal product • Gibberella fugikuroi • Many other pathogens • Plant Product • Normal growth and elongaton

  34. O C=O HO OH CH3 C CH2 HO O GA1 Gibberellins

  35. Gibberellins • Inactive Active

  36. Gibberellins • Synthesis • Starts in Plastids (Carotenoid Pathway) • Modified in ER • Completed in Cytoplasm • Tissue Localization • SAM, Young Leaves, Apical Internodes • Developing Fruit, Germinating Seed • Roots • Transport • Xylem and Phloem

  37. Gibberellins • Responses • Cell Elongation • Dwarf cultivars eg. Peas (Little Marvel) • Dwarfing rootstocks apples, pears, peaches height from roots fruit quality from scion • Seed Dormancy High ABA Reversed by GA application Synthesis of GA by embryo

  38. Gibberellins

  39. Gibberellins • Agricultural Uses • 1. Thompson Seedless Grapes Principal use Parthenocarpic Fruit • 2. Seed Germination Malting Barley Precocious germination • 3. Male Flower production Monoecious & Dioecious Plants • 4. Chilling Requirement Azaleas Biennials Biennial Bearing

  40. H H C = C H H Ethylene

  41. Ethylene • C2H4 • Gas at room temperature • Synthesis |Hemicellulose +ATP | Methionine ---> SAM ---> ACC ---> Ethylene ---> PG 1 2 | 3 |Galactose • 1. S-Adenosyl Methionine • 2. Amino Cyclo Propane • 3. Polygalacturonase

  42. Ethylene • Agricultural Uses • Ethaphon - 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 Canning Tomatoes Mechanical Harvest

  43. Ethylene • 2. Floral Development Bromeliads Pineapple Banana Uniform development of inflorescence • 3. Sex Expression Female Flowers Curcubits opposite of GA action • 4. Degreening of Citrus Oranges, Lemons, Grapefruit Break down Chlorophyll Leaves Carotenoids

  44. Ethylene • 5. Mechanical Harvesting Formation of Abscission Zone Stimulate Fruit Drop Cherries, Walnuts, Pecans • 6. Postharvest Shelf Life block ethylene synthesis AgNO3 or Silver Thiosulfate delay senescence Carnations

  45. O CH3 CH3 CH3 C OH OH O CH3 Abscisic Acid

  46. Abscisic Acid • Natural Plant Growth Retardant Opposes action of GA and Auxin • Synthesis Chloroplasts Breakdown product of Carotenoids

  47. Abscisic Acid • Responses • Dormancy Maintenance high levels in dormant seed and buds • Drought Resistance causes stomatal closure • Agricultural Uses None

  48. Synthetic Growth Retardants 1. Daminozide (Alar, B-9) Retard growth Stimulate Flowering Chrysanthemums, Azaleas Chemical Pruning Apple Enhance size and color • 2. Chlormequat (CCC, Cycocel) Promote branching Poinsettia, Geraniums, Bouganvillia Prevent Lodging of Wheat

  49. Synthetic Growth Retardants • 3. Ancymidol (A-Rest) Height Control of bulb produced plants Lily, Tulip • 4. Paclobutrazol (Bonzai) Micropropagation Stimulates Rooting

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