1. Plant and Soil Science I Standard 5: Students will describe plant anatomy and physiology concepts Objective 7: Explain the management of plant growth and development

2. Objectives A.Describe the role of the apical meristem in plant growth. B.Identify plant hormones and explain their functions. C.Explain plant tropisms. D.Differentiate between synthetic growth regulators and plant hormones. E.Describe the benefits of using plant growth regulators.

3. A. Describe the role of the apical meristem in plant growth. Meristems; a plants fountain of youth! Meristem: the site of actively dividing cells resulting in plant growth Apical (or terminal) bud: located at the end of a stem or root and gives the plant height or length Axillary (or lateral) bud: located on side of a stem and give the plant girth Apical dominance: the apical tip grows taller and longer inhibiting the growth of lateral buds

4. A. Describe the role of the apical meristem in plant growth.

5. A. Describe the role of the apical meristem in plant growth. Meristems The meristimatic region on plants are found at tip of the outer cells on roots or shoots Changing the apical dominance is as simple as removing the top cells from a plant shoot

6. A. Describe the role of the apical meristem in plant growth. Ouch, that hurt aka ‘pinching plants’ Pinching plants is a form of pruning that encourages branching Pinching plants alters the apical dominance Pinching the plant forces the plant to focus on growing lost stems, rather than growing height

7. A. Describe the role of the apical meristem in plant growth. How to pinch plants 1.Find a node on the plant you want to pinch. 2.Using a knife, scissors, or your fingers remove (pinch) the lateral shoot above the node.

8. B. Identify plant hormones and explain their functions. What are hormones? What is a hormone? What do hormones do? Can you think of any examples? Chemical Messenger Causes a change in how the body works Travel in the blood, secreted by glands Control Growth, blood sugar, sex development, mood, metabolism. Insulin Testosterone Oestrogen Glucagon ADH HGH

9. B. Identify plant hormones and explain their functions. Hormones in plants What do hormones control in plants? Roots and shoots Seed germination Leaf fall Disease resistance Fruit formation and ripening Flowering time Bud formation Anything related to plant growth!

10. B. Identify plant hormones and explain their functions. Hormones Naturally produced in the plant Some are commercially important and can be used to to produce plants as ornaments or food Some have different effects on different tissues

11. B. Identify plant hormones and explain their functions. Two types of hormones Promoters vs. Inhibitors – Promoters- cause faster growth – Inhibitors- reduce growth Also called a growth retardant

12. B. Identify plant hormones and explain their functions. Hormones Auxins Gibberellins Cytokinins Ethylene Abscisic acid

13. B. Identify plant hormones and explain their functions. Hormones in a nutshell HormoneEffects Auxins Cell enlargement and differentiation Giberellins Cell enlargement and differentiation Cytokinins Cell division Abscisic Acid Dormancy Ethylene Ageing

14. B. Identify plant hormones and explain their functions. Auxins Promote cell elongation One of the first hormones discovered in science by Charles Darwin The primary auxin is indoleastic acid (IAA) There is a greater concentration of auxins in the apical meristems, hence apical dominance Passed from cell to cell through their cell walls Promoter

15. B. Identify plant hormones and explain their functions. Giberellins Induce cell elongation and cell division Produced in the stem and root apical meristems, seed embryos and young leaves Important for plant growth and development through flowering and/or seed germination Promoter

16. B. Identify plant hormones and explain their functions. Cytokinins Responsible for cell division and differentiation Produced in the roots and transported through xylem Aid in growth of lateral shoots Inhibit branching of roots Promoter

17. B. Identify plant hormones and explain their functions. Abscisic Acid Growth inhibiting hormone Plays a key role in seed dormancy Causes stomates to close in drought conditions to conserve water Growth retardant

18. B. Identify plant hormones and explain their functions. Ethylene Colorless gas that is emitted by aging plants It is produced in plant stems, ripening fruit and dying leaves Converts starch into sugar Growth retardant

19. C. Explain plant tropisms. Sensitivity – Responding to the environment Plants respond to stimuli in order to: Avoid stress Avoid being eaten Enhance survival Improve chances of having offspring The way a plant grows is controlled by hormones Plants response to external stimuli is known as a tropism

20. C. Explain plant tropisms. The ‘tropisms’ Phototropism Gravitropism or Geotropism Chemotropism Thigmitropism Hydrotropism

21. C. Explain plant tropisms. Stimulus vs. response Stimulus: something that influences an activity Response: any behavior that results from the stimulus Examples: StimulusResponse Lack of foodHungry No waterThirsty Lollipops, ponies, and Ferris wheels Happy

22. C. Explain plant tropisms. Step 1 – Make a copy of this table in your notes TropismStimulusResponse Phototropism Gravitropism Chemitropism Thigmitropism Hydrotropism

23. C. Explain plant tropisms. Step 2 – Observe the following pictures to complete the table TropismStimulusResponse Phototropism Gravitropism Chemitropism Thigmitropism Hydrotropism

24. C. Explain plant tropisms.

26. Important minerals in soil

27. C. Explain plant tropisms.

29. C. Explain plant tropisms. Step 3 – Review your observations TropismStimulusResponse Phototropism Light sourceStems bend or stretch (etiolation) towards light Gravitropism GravityStems curve upward on a plant that is laid on its side Chemitropism Nutrients in the soilRoots grow to nutrients in soil Thigmitropism Mechanical stimuliTendrils on a cucumber plant touching an object and curling around it for support Hydrotropism Water sourceRoots grow to water

30. C. Explain plant tropisms. What controls tropisms? The hormone auxin controls most tropisms Auxin promotes cell growth Phototropism – Sunlight breaks down auxin – Plant stems indirect sunlight will have the least amount of auxin – Area of the plant that is more shaded will have more auxin – More cell growth on shaded side – Plant bends towards light

31. Light directly over the plant Auxins are in equal quantity Cell elongation is equal on all sides of the cell Greater light on the right side of the plant Auxin quantity becomes greater on the left cell Auxins trigger cell elongation on the left side Plant ‘stretches’ to the light

32. C. Explain plant tropisms. What controls tropisms? The hormone auxin controls most tropisms Auxin promotes cell growth Gravitropism – The plant stem that was once upright is on its side – The auxin are settle on the bottom side of the stem – More auxin accumulate on the stems bottom side – More cell growth occurs on bottom side – Plant bends upward

33. D. Differentiate between synthetic growth regulators and plant hormones. What’s the difference? Plant growth regulators (PGR’s) modify the plants physiological processes Hormones modify the plants physiological processes One is created by the plant the other is created in a factory!

34. D. Differentiate between synthetic growth regulators and plant hormones. Natural vs. Synthetic Natural vs. Synthetic – Natural- found naturally in plants – Synthetic- human made Both groups regulate or influence: – Cell division – Cell differentiation – Root and shoot growth – Senescence (plant aging)

35. D. Differentiate between synthetic growth regulators and plant hormones. Types of PGR’s Promoters vs. Inhibitors – Promoters- cause faster growth – Inhibitors- reduce growth Used on florist crops such as poinsettia & chrysanthemum. – They slow elongation of stems, making sturdier, fuller plants PGR’s have been created to model plant hormones

36. D. Differentiate between synthetic growth regulators and plant hormones. PGR’s Growth retardants can be used on hedges and lawns to slow growth and decrease maintenance. TREATED UNTREATED

37. D. Differentiate between synthetic growth regulators and plant hormones. Synthetic and natural growth retardants Synthetic and natural growth retardants are sold under the trade names A-Rest ®, B-Nine ®, Bonzi ®, Sumagic ®, Cycocel ®, and others The different names are used on different horticulture plants

38. E. Describe the benefits of using plant growth regulators. Improve the quality and quantity Plant growth regulators improve the quality and quantity of agriculture commodity yields Most of the plant growth regulators are naturally produced by the plant

39. E. Describe the benefits of using plant growth regulators. Auxins Speed up the rooting of plant cuttings – Indoleacetic acid (IAA) – Indolebutyric acid (IBA) Prevent pre-harvest fruit drop on apples – Naphthaleneacetic acid (NAA)

40. E. Describe the benefits of using plant growth regulators. Gibberellins Induces flowering Growth stimulant to make larger stalks and fruit

41. E. Describe the benefits of using plant growth regulators. Ethylene Promotes fruit ripening Used for ripening fruit before it is placed on grocery shelves Pineapples will bloom when treated with ethylene. – In commercial greenhouses, the product used for ethylene generation is Florel ® or ethephon.

42. E. Describe the benefits of using plant growth regulators. Cytokinins Cytokinins promote cell division and enlargement to promote senescence Leaves grow themselves to death

43. E. Describe the benefits of using plant growth regulators. Plant growth regulators Prevents lodging in cereal crops Prevents pre-harvest fruit drop Synchronizes maturity to allow mechanical harvesting Harvesting maturity to decrease turnover time Historically common PGR’s – 2-4D – 2-4-5T (agent orange)

44. E. Describe the benefits of using plant growth regulators. Pinching agents Pinching agent chemicals are used commercially to kill terminal vegetative buds. – They promote branching & a more bushy, attractive plant. OffShoot-0 ® & Atrimmec ® are mainly used for this purpose.

45. E. Describe the benefits of using plant growth regulators. Vitamins Vitamins are sold occasionally as stimulants for plant growth and for use after transplanting Vitamin effectiveness has not been determined fully –Limited experiments Overall, it is very possible that vitamins do improve plant growth in some cases – They should never be used in place of fertilizers or proven-effective chemicals sold for use on plants