1. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Monocot or Dicot?

2. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Monocot or Dicot?

3. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Monocot or Dicot

4. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Monocot or Dicot?

5. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Monocot or Dicot?

6. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Monocot or Dicot?

7. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Monocot or Dicot?

8. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Monocot or Dicot? MonocotDicot

9. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Monocot or Dicot? DICOTMONOCOT

10. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Monocot or Dicot DICOTMONOCOT

11. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Monocot or Dicot? Dicot

12. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Monocot or Dicot? Dicot

13. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Monocot or Dicot? Dicot

14. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Monocot or Dicot? Monocot

15. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings PowerPoint Lectures for Biology, Seventh Edition Neil Campbell and Jane Reece Lectures by Chris Romero Chapter 39 Plant Responses to Internal and External Signals

16. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 39.2: Plant hormones help coordinate growth, development, and responses to stimuli Hormones are chemical signals that coordinate different parts of an organism

17. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Discovery of Plant Hormones Any response resulting in curvature of organs toward or away from a stimulus is called a tropism Tropisms are often caused by hormones

18. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings A Survey of Plant Hormones In general, hormones control plant growth and development by affecting the division, elongation, and differentiation of cells Plant hormones are produced in very low concentration, but a minute amount can greatly affect growth and development of a plant organ

19. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

20. Auxin—Made in the shoot tips sent to the roots. Stimulate cell elongation in the meristems. Auxin stimulates growth in the apical meristems but inhibits growth in the lateral (axillary). – Remember primary and secondary tumors… This is called apical dominance—but when you snip the apical meristems off a plant the lateral buds begin to grow—the auxin is no longer inhibiting the growth of the lateral meristems.

21. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

22. LE 39-9 Intact plant Plant with apical bud removed Lateral branches “Stump” after removal of apical bud Axillary buds

23. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

24. Cytokinins—made in root tips sent to shoots. Produced in the growing roots and in developing fruits and seeds. Stimulate cell division and interact with auxins to control the growth of the new organ in injured plants and to balance root and shoot growth.

25. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

26. Gibberellins Gibberellins have a variety of effects, such as stem elongation, fruit growth, and seed germination

27. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Stem Elongation Gibberellins stimulate growth of leaves and stems In stems, they stimulate cell elongation and cell division

28. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Fruit Growth In many plants, both auxin and gibberellins must be present for fruit to set Gibberellins are used in spraying of Thompson seedless grapes

29. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

32. Abscisic Acid Two of the many effects of abscisic acid (ABA): – Seed dormancy Inhibits growth once embryo is fully developed and awaiting environmental cues for completion. – Drought tolerance (stop growing until resources available)

33. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Drought Tolerance ABA is the primary internal signal that enables plants to withstand drought

34. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Ethylene Plants produce ethylene in response to stresses such as drought, flooding, mechanical pressure, injury, and infection

35. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Triple Response to Mechanical Stress Ethylene induces the triple response, which allows a growing shoot to avoid obstacles The triple response consists of a slowing of stem elongation, a thickening of the stem, and horizontal growth

36. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Apoptosis: Programmed Cell Death A burst of ethylene is associated with apoptosis, the programmed destruction of cells, organs, or whole plants

37. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Leaf Abscission Ethylene plays a role in causing plants to seal off the base of the structure and drop organs that are no longer needed. – Example—petals dropping after flowers have been pollinated – Leaves dropping in autumn – Fruit dropping after they’ve ripen

38. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

39. Fruit Ripening A burst of ethylene production in a fruit triggers the ripening process

40. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings TROPISM IN PLANTS Growth in response to light, gravity and touch. – Phototropism Growing toward light – Gravitropism Stems grow against gravity, roots with gravity – Thigmotropism Detect and wrap around objects using tendrils