2. Yes - By adjusting their pattern of growth and development. In DarkIn Light ???Question?? ? Do plants sense and respond to their environment ?

3. In Dark ???Question?? ? Plant in dark spends its energy by elongating its stems… to “get out of the dark”

4. ???Question?? ? In the light, leaves grow, roots elongate, and the shoot produces chlorophyll (takes a lot of energy… but it will be photosynthesizing!!) In Light

5. THOUGHT….. Animals respond to stimuli by changing behaviorAnimals respond to stimuli by changing behavior

6. Hobby Comment: Plants can’t “move” away from a stimulus, but can change their growth response. Result – plant bodies are more “flexible” in morphology than animals. Plants respond to stimuli by changing growth patternsPlants respond to stimuli by changing growth patterns

7. Classical Example Phototropism - plant growth response to unilateral light.Phototropism - plant growth response to unilateral light. Observation – plants bend or grow towards the light.Observation – plants bend or grow towards the light.

8. What mechanism causes this response? Signal Transduction PathwaySignal Transduction Pathway

9. what is going on with the plant cells?

11. The tip of the coleoptile senses light

12. positive phototropism

13. without the tip, no sense of light

14. cover the tip, no sense of light

15. cover the tip with transparent cap, senses light positive phototropism

18. can’t diffuse down, no sense of light

19. cells on the dark side - elongate faster than cells on the light

20. Went Experiments

21. Plant Hormones Auxins Cytokinins Gibberellins Brassinosteriods Abscisic Acid Ethylene

23. Promotes cell elongation and growth of stems & roots shoot tip base

24. Cause of Phototropism - this is how auxin works causes pH to lower enzymes Enzymes called expansins break the H-bonds between cellulose / loosen the cell wall.

25. this is how auxin works

26. Monocots can inactivate SYNTHETIC auxins… Eudicots cannot… GREAT BROADLEAF WEED KILLER IN YOUR LAWN!!

27. Question What is the adaptive value of phototropism ? It tilts the leaves toward the light source for more efficient photosynthesis.

28. GEOTROPISM Auxin causes:

32. Promotes cell elongation and growth of stems & roots @ meristem regions

33. Auxin Causes Mimosa Rapid Leaf Movement Auxin causes:

34. Grape tendrils Auxin causes:

35. stimulate cell division / mitosis

36. works together with AUXIN

37. Promotes growth of root low [cyto] high [auxin]

38. Promotes growth of shoot high [cyto] high [cyto] low [auxin] low [auxin]

39. Promotes apical dominance

40. Promotesanti-aging

41. Stem elongation

42. have GA3 lack GA3

43. have GA3 promotes internode elongation

44. Fruit growth Extra GA3 No GA3

45. seed germinatio n

46. Slows down the dr op pi ng of leaves

47. promotes seed dormancy

48. "Stress" hormone produced under unfavorable conditions. Closes stomates quickly "Stress" hormone produced under unfavorable conditions.

49. Stimulates fruit ripening

50. fruit ripening One rotten apple DOES spoil the whole bunch!

51. fruit ripening Put an apple in w/ your green banannas

52. apoptosis Death of flower after pollination,

53. apoptosis death of xylem cells, leaves falling off the trees

54. Flowering Types: 1.Short - Day Plants (long-night plants) 2. Long - Day Plants (short-night plants) 3. Day - Neutral Plants

55. Night Length Actually controls flowering response, not day length. Proof – experiments show that if you interrupt the dark period, you reset the “clock”.

56. Short-Day Plants Flower when days are shorter than a critical period (long nights). Ex: Mums Poinsettias

57. Long-Day Plants Flower when days are longer than a critical period (short nights). Ex: Spinach Iris Lettuce

58. Day-Neutral Plants Flower whenever they have enough energy. Ex: Roses African Violets

59. Anatomy of a twig