1 / 81

Chapter 39: Control Systems in Plants

Chapter 39: Control Systems in Plants. Question. Do plants sense and respond to their environment ? Yes - By adjusting their pattern of growth and development. In Dark. In Light. Comment. Plants can’t “move” away from a stimulus, but can change their growth response.

upton-hanson
Download Presentation

Chapter 39: Control Systems in Plants

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Chapter 39:Control Systems in Plants

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

  3. 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.

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

  5. Phototropism Experimenters • Darwins: late 1800's. • Boysen & Jenson: early 1900's. • F.W. Went: 1926

  6. Went Experiments

  7. Mechanism of Phototropism • Cells on the dark side elongate faster than the cells on the light side. • The uneven growth rate causes the bending of the stem toward the light.

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

  9. Cause of Phototropism • Chemical messenger from the tip caused the growth response in the stem. • The distribution of the chemical changes in the unequal light, resulting in unequal cell elongation.

  10. Hormone • Chemical signal produced in one location, transported, has effect in another location. • Phototropism is caused by a plant hormone.

  11. Plant Hormones • Are produced in small quantities. • Effects may reflect balance between several hormones.

  12. Mechanism

  13. Plant Hormones 1. Auxins 2. Cytokinins 3. Gibberellins 4. Abscisic Acid 5. Ethylene

  14. Auxins • Named by Went in 1926. • First plant hormone described. • Ex: IAA (natural) 2,4-D (synthetic)

  15. Major Functions • Stimulates cell elongation. • Fruit development. • Apical Dominance. • Tropism responses.

  16. Apical Dominance

  17. Where Produced • Apical Meristems. • Young leaves. • Embryos.

  18. Cytokinins • Isolated from coconut "milk" (endosperm) in the 1940’s. • Named because they stimulate cell division. • Ex: Zeatin

  19. Major Effects • Stimulates cell division. • Delays senescence. • Root growth and differentiation. • Where Produced - roots

  20. Control shoot or root differentiation in tissue cultures. Auxin/Cytokinin Ratios

  21. Gibberellins • Found from the "Foolish Seedling" disease in rice. • Ex: GA3 70 types known

  22. Foolish Seedlings

  23. Internode elongation. Seed/Bud germination. Flowering (some species). Fruit development. Major Effects Extra GA3 No GA3

  24. Have GA3 Lack GA3

  25. Where Produced • Apical Meristems. • Young leaves. • Embryos.

  26. Abscisic Acid • Slows or inhibits plant growth. • "Stress" hormone produced under unfavorable conditions.

  27. Major Effects • Inhibits growth • Seed/Bud dormancy. • Stomata closure. • Leaf drop – produces abscission layer.

  28. Abscission Layer

  29. Where Produced • Leaves • Stems • Green fruit

  30. Ethylene • Gaseous hormone (fast diffusion rates). • Often interacts with Auxin.

  31. Major Effects • Fruit ripening. • Accelerates Senescence. • Stem/Root Elongation (+ or -).

  32. Where Produced • Ripening fruits. • Senescent tissue. • Nodes.

  33. New Hormones • Oligosaccharins – short chains of sugars released from the cell wall. • Function: • Pathogen responses • Cell differentiation • Flowering

  34. New Hormones • Brassinosteroids – steroid hormones similar to animal sex hormones. • Function: • Needed for normal growth and development.

  35. Commercial Applications of Plant Hormones • Weed killers • Seedless fruit • Rooting of cuttings • Tissue culture

  36. Plant Movements 1. Tropisms 2. Circadian Rhythms

  37. Tropisms • Growth responses in response to external stimuli. • + toward a stimulus • - away from stimulus

  38. Examples 1. Phototropism 2. Gravitropism

  39. Phototropism • Response to light (blue).

  40. Movie

  41. Gravitropism • Response to gravity. • Stems are – gravitropic and roots are + gravitropic.

  42. Statolith movement may be the receptor for the stimulus. Gravitropism - mechanism

  43. Thigmotropism • Response to touch. • A series of 5 genes are involved. • Ex: Tendrils Climbing stems Wind direction response of stems.

  44. Turgor Movements • Movement caused by turgor pressure differences in certain cells.

  45. 1. Rapid Leaf Movement Ex: Mimosa 2. Sleep Movements Ex: Bean Leaves Prayer Plant Types Sleep Movements Day Night

  46. Mimosa Rapid Leaf Movement

  47. Circadian Rhythms • A physiological cycle about 24 hours long. • Ex: Stomata opening Sleep movements

More Related