Plant Growth Regulator PPT.pptx

Plant growth regulators (PGRs) are chemicals used to modify plant growth such as increasing branching, suppressing shoot growth, increasing return bloom, removing excess fruit, or altering fruit maturity. Numerous factors affect PGR performance including how well the chemical is absorbed by the plant, tree vigour and age, dose, timing, cultivar, and weather conditions before, during, and after application.

Plant growth regulators can be grouped into five classes: compounds related to auxins, gibberellins and inhibitors of gibberellin biosynthesis, cytokinins, abscisic acid and compounds affecting the ethylene status. Products that block the biosynthesis of plant hormones are also available (Apogee, Retain)

The five groups of plant growth regulators used in fruit crops include:

Auxins: These are growth promoting substances that contribute to the elongation of shoots, but at high concentrations they can inhibit growth of lateral buds. In addition to being used as plant growth regulators, auxins can also be herbicides (2, 4-D etc.). In apple production napthaleneacetic acid (NAA) is a synthetic auxin that can be used to thin fruit and prevent fruit drop shortly before harvest. For more information on the use of products for thinning see Ontario.ca/apples and find Thinning of Tree Fruit.

Gibberellins: Gibberellins (GA) promote cell elongation, shoot growth, and are involved in regulating dormancy. Promalin®/Perlan® (containing GA4+7 and 6-benzyladenine) have been used to improve fruit size and reduce russetting in apples. ProGibb 40SB and Falgro (containing GA3) are used to delay ripening, improve fruit firmness and extend the harvest period in sweet cherries. Gibberellins are used in tart cherries to manage flowering to avoid over production. Apogee or Kudos 27.5 WDG® (Prohexidione-calcium) inhibits the biosynthesis of gibberellins. Apogee or Kudos 27.5 WDG are used to modify the morphology of trees (apple and cherries) and to control runner production in strawberries.

Cytokinins: Cytokinins promote cell division. Cytokinins are involved in branching and stimulating bud initiation. They are used as fruit thinners (Maxcel® or Cilis Plus® 6-BA) in apples. For more information on the use of these products for thinning see Ontario.ca/apples and find Thinning of Tree Fruit.

Absicisic Acid: Absicsic acid controls the dormancy of buds and seeds, inhibits shoot growth and is involved in regulating water loss from plants.

Ethylene: Ethylene promotes abscission of leaves and fruits, inhibits shoot elongation and inhibits lateral bud development. In apples and cherries, ethylene is involved in the transition of fruit from being physiologically mature to ripe. Ethephon (Ethrel®) is a synthetic compound that releases ethylene upon application. Retain interferes with ethylene biosynthesis and allows fruit to hang on trees longer and lengthens storage life.

1. Plant Growth Hormones Amrinder Singh Ph.D Scholar

2. Plant Growth and Development Hormones diffuse throughout the plant to promote growth and development.

3. What is a Plant Hormone? A naturally-occurring compound which regulates change in physiology , growth or development of the plant.

4. 5 Types of Plant Hormones Auxin Cytokinin Gibberellin Abscisic Acid Ethylene

5. Auxin Role of Hormone Cell elongation (increase cell size) Site of Production Shoot Tips Effect of Hormone Growth of plant in response to the environment, production of roots. Tropism : a plant’s response to environment Phototropism - response to light Geotropism -response to gravity Thigmotropism -response to touch

6. Auxin Growth Effects Stimulates Adventitious Root Formation . Adventitious roots grow from stems or leaves rather than from the original root system of the plants. This is especially useful when cutting and transplanting plants.

7. Auxin Growth Effects Thigmotropism-touch Phototropism-light Geotropism-gravity Tropisms- How a plant grows in response to the environment

8. Auxin How does this hormone stimulate tropism? Cell Elongation Auxin travels away from the sunlight and expands the cells

9. Cytokinin Role of Hormone Cell division (increase number of cells) Site of Production Root Tips Effect of Hormone Mitosis of new cells; Stimulates seed germination and new shoot growth

10. AUXIN stimulates the production of roots . CYTOKININ stimulates the production of shoots .

11. Gibberellin Role of Hormone Internode Elongation (height) Site of Production Root and Shoot Tips Effect of Hormone Controls yearly cycles (flowering/bolting, seeding and dormancy exiting) Rapid growth of stems and seeds.

12. Internode Elongation Internode: the part of the plant between two nodes or joints. Node : the part of the stem where stems leaves and buds emerge; point at which stems intersect and branch.

13. Gibberellin and Cycle Control How gibberellin in a plant recognizes seasonal changes Photoperiod : a plant’s recognition of daylight length in a 24 hour period. As daylight increases in the spring, the plant recognizes a longer photoperiod. Gibberellin triggers the plant to exit dormancy.

14. Why is it called Gibberellin? Japanese rice farmers discovered a fungus ( Gibberella fujikuroi ) that caused an increase in this hormone. From this, they learned that plants have a hormone that causes shoot and seed growth. They named this hormone, “ Gibberellin ”, after the fungus.

15. Gibberellin Growth Effects Increases plant height Increases fruit size

16. Abscisic Acid Role of Hormone Dormancy Site of Production Chloroplasts Effect of Hormone Enters dormancy: (leaves drop off trees, seeds fall, the stomata close to reduce water loss during drought stress)

17. Abscisic Acid Abscisic Acid in a plant recognizes seasonal changes Dormancy : a period of no growth As daylight decreases in the winter, the chloroplasts in the plant recognize a shorter photoperiod. Abscisic Acid triggers the plant to enter dormancy. The flowers, seeds and leaves fall from the trees

18. Ethylene Role of Hormone Ripening and Death Site of Production Ripening fruits, aging flowers, germinating seeds and wounded tissues Effect of Hormone Stimulates fruits to ripen, flowers to enter senescence (to grow old and die)

19. What causes my fruits and veggies to go bad? The answer is ETHYLENE! Ethylene is the only plant hormone that exists in a gas form. It can be synthesized from anywhere in the plant. It can even diffuse outside the origin plant and affect another plant nearby.

20. Is Ethylene good or bad? A gas that speeds up plant death?!! How is this good news?! Examples: flowers or fruit that are not “ripe” need ethylene to reach their peak

21. If the amount of Auxin is greater than Cytokinins… Auxin Cytokinis Shoots grow less rapidly, while root growth is dramatically increased How do these Hormones Work Together?

22. If the amount of Cytokinins is greater than Auxin … How do these Hormones Work Together? Shoot growth is dramatically increased, while roots grow is less rapidly.

23. If the amount of Cytokinins is greater than Auxin … Flowers are no longer blooming and leaves begin to fall from the trees. How do these Hormones Work Together?

24. If the amount of Cytokinins is greater than Auxin … Green leaves and flowers begin to regrow . This usually occurs in the spring time. How do these Hormones Work Together?

25. In summary… Auxin Produces Roots Cell elongation Acts through t ropism responses Cytokinin Produces new Shoots Mitosis of new cells Seed Germination Gibberellin Promotes Internode elongation Controls yearly cycles Abscisic Acid “Dormancy hormone” Causes leaves to drop and stomatas to close Ethylene “Death Hormone” Speeds up ripening and senescence

26. Thank You