Plant growth regulators


Published on

Plant hormones (also known as plant growth regulators (PGRs) and phytohormones) are chemicals that regulate a plant's growth. Plant hormones on the other hand, are not like animal hormones, they are often not transported to other parts of the plant and production is not limited to specific locations. Plants lack tissues or organs specifically for the production of hormones; unlike animals, plants lack glands that produce and secrete hormones to be moved around the body. Plant hormones shape the plant, effecting seed growth, time of flowering, the sex of flowers, its longevity, senescence of leaves and fruits, they affect which tissues grow up and which grow downward, leaf formation and stem growth, fruit development and ripening, and even plant death. Hormones are vital to plant growth and lacking them plants would be mostly a mass of undifferentiated cells.

Published in: Technology, Business
  • Thanks in advance
    Are you sure you want to  Yes  No
    Your message goes here
  • I would be grateful if this presentation can be sent to my email.
    Are you sure you want to  Yes  No
    Your message goes here
  • please i need this presentation, thanks in advance. my email is
    Are you sure you want to  Yes  No
    Your message goes here
No Downloads
Total views
On SlideShare
From Embeds
Number of Embeds
Embeds 0
No embeds

No notes for slide

Plant growth regulators

  1. 1. Plant Growth Regulators Chemical Messengers Bio-Resource:
  2. 2. Hormones •In plants, many behavioral patterns and functions are controlled by hormones. These are “chemical messengers” influencing many patterns of plant development. oPlant hormones – a natural substance (produced by plant) that acts to control plant activities. Chemical
  3. 3. Hormones •Are produced in one part of a plant and then transported to other parts, where they initiate a response. •They are stored in regions where stimulus are and then released for transport through either phloem or mesophyll when the appropriate stimulus occurs.
  4. 4. Growth Regulators •Plant growth regulators – include plant hormones (natural & synthetic), but also include non-nutrient chemicals not found naturally in plants that when applied to plants, influence their growth and development.
  5. 5. Growth Regulators •5 recognized groups of natural plant hormones and growth regulators. o1. Auxins o2. Gibberellins o3. Cytokinins o4. Ethylene o5. Abscisic acid
  6. 6. Auxins •Influence plant growth – found in leaves and stems – growth regulators and hormones •Cell enlargement or elongation – located in meristems and shoot tips (terminal & lateral buds). Auxins move mainly from apex (top) down. •Lengthening of the internodes and influence the developing embryos in the
  7. 7. What happens when auxin is added to a stem. The stem will bend away from the auxin. It elongates faster on the extra auxin side.
  8. 8. Auxins •Apical dominance – high levels of auxin in the stem just above lateral buds block their growth (blockage of growth of lateral buds by presence of terminal buds). If shoot tip is removed. The auxin level behind the lateral buds is reduced and the lateral buds begin to grow. (the auxin which formed the blockage to keep lateral buds small is reduced so
  9. 9. Auxins •Photo (light) and geotropism (gravity) – involved in tropism responses – positive responses •Flower initiation and development •Root initiation and development (rootone) – used on cuttings to help stimulate root growth
  10. 10. Auxins (IAA) •Plant Growth Regulators - Indobutyric acid (IBA)(synthetic), napthaleneacetic acid (NAA)(synthetic), 2,4- dichlorophenoxyacetic acid (2-4D) (synthetic) •Hormone - indoleactic acid (IAA) (naturally occurring).
  11. 11. Auxin
  12. 12. Gibberellins (GA) •Gibberellic Acid •Have a regulatory function •Are produced in the shoot apex primarily in the leaf primordial (leaf bud) and root system •Stimulates stem growth dramatically
  13. 13. Gibberellins (GA) •Stimulates cell division, cell elongation (or both) and controls enzyme secretions. Ex: dwarf cultivars can be treated with GA and grow to normal heights – indicates dwarf species lack normal levels of GA
  14. 14. Gibberellins •Involved in overcoming dormancy in seeds and buds. •GA translocates easily in the plant (able to move freely) in both directions – because produced in not only shoot apex but also in the root structure.
  15. 15. Gibberellins •Used commercially in: oIncreasing fruit size of seedless grapes oStimulating seed germination & seedling growth
  16. 16. Gibberellins •Promoting male flowers in cucumbers for seed production. •Overcoming cold requirements – for some seed, application of GA foregoes the cold requirements (some seed require to be frozen or placed in the refrigerator for a period of time before they will germinate).
  17. 17. Cytokinins •Promotes cell division •Found in all tissues with considerable cell division. oEx: embryos (seeds) and germinating seeds, young developing fruits
  18. 18. Cytokinins •Roots supply cytokinins upward to the shoots. •Interact with auxins to influence differentiation of tissues (may be used to stimulate bud formation).
  19. 19. Cytokinins •As roots begin to grow actively in the spring, they produce large amounts of cytokinins that are transported to the shoot, where they cause the dormant buds to become active and expand.
  20. 20. Cytokinins •Tissue cultures use cytokinins to induce shoot development •Cytokinins may slow or prevent leaf senescence (leaf ageing or leaf fall).
  21. 21. Cytokinin
  22. 22. Ethylene •Gaseous hormone •Produced in the actively growing meristems of the plant, in senescing ripening or ageing fruits, in senescing (ageing or dying) flowers, in germinating seeds and in certain plant tissues as a response to bending, wounding or bruising. •Ethylene as a gas, diffuses readily throughout the plant.
  23. 23. Ethylene •May promote leaf senescing and abscission (leaf fall). •Increases female flowers in cucumbers (economically - will increase fruit production). •Degreening of oranges, lemons and grapefruit – ethylene gas breaks down chlorophyll and lets colors show through.
  24. 24. Inhibitors •Abscisic Acid (ABA) oWidespread in plant body – moves readily through plant oABA appears to be synthesized (made) by the leaves. oInteracts with other hormones in the plant, counteracting the growth – promoting the effects of auxins &
  25. 25. Abscisic Acid •Involved with leaf and fruit abscission (fall), onset of dormancy in seeds and onset of dormancy (rest period) in perennial flowers and shrubs •ABA is effective in inducing closure of stomata in leaves, indicating a role in the stress physiology in plants. (ex: increases in ABA following water, heat and high salinity stress to the plant)
  26. 26. Thank You.... Bio-Resource: