Biology - Chp 23-25 - Selected Plant Topics - PowerPoint

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Biology - Chp 23-25 - Selected Plant Topics - PowerPoint

  1. 1. Selected Plant Topics Chapters 23 – 25
  2. 2. Specialized Tissues in Plants 23 -1
  3. 3. Seed Plant Structure• Three of the principal organs of seed plants are roots, stems, and leaves
  4. 4. Roots• Absorb water and dissolved nutrients• Anchor plants in the ground• Hold soil into place and prevent erosion
  5. 5. Stems• Support above ground parts of plant• Transports nutrients
  6. 6. Leaves• Main photosynthetic systems• Let in oxygen and carbon dioxide
  7. 7. Vascular Tissue• Forms a transport system that moves water and nutrients throughout the plant
  8. 8. Types of vascular tissue• Xylem – brings water and nutrients up from the roots• Phloem – brings food down from the leaves
  9. 9. Leaf Structures and Functions• Mesophyll – where photosynthesis happens• Palisade mesophyll – closely packed, lots of chloroplasts• Spongy mesophyll – loose tissue with many airspaces
  10. 10. • Stomata – pore-like openings in the underside of the leaf• Allow CO2 and O2 to diffuse in and out of the leaf
  11. 11. Guard Cells• Control the opening and closing of the stomata by responding to changes in water pressure
  12. 12. Transpiration• The loss of water through its leaves
  13. 13. Gas Exchange• If stomata were kept open all the time, water loss due to transpiration would so great that few plants would be able to take in enough water to survive.• Plants keep their stomata open just enough to allow photosynthesis to take place but not so much that they lose too much water.• The stomata open and close in response to changes in water pressure in the guard cells
  14. 14. • When pressure is high – stomata open• When pressure is low – stomata closeQ: What time of day do you think stomata are open and why?A: Daytime, cause that’s when photosynthesis happens
  15. 15. 24 – 1 Reproduction with Cones and Flowers
  16. 16. Life Cycle of Gymnosperms• Reproduction in gymnosperms takes place in cones• Male cones produce – pollen grains• Female cones produce – ovules
  17. 17. Structure of Flowers• Flowers are reproductive organs that are composed of 4 kinds of specialized leaves
  18. 18. Sepals• Enclose the bud before it opens, leaf- like
  19. 19. Petals• Brightly colored, attract insects to flower
  20. 20. Stamen• Male reproductive structure of flower, Anther made of 2 parts• Filament – long, thin, stalk that supports the anther• Anther – makes Filament pollen grains Anther + Filament = Stamen
  21. 21. Pistil• Female reproductive structure, made of 3 parts
  22. 22. Stigma• where pollen grains land, sticky
  23. 23. Style• Connects stigma to ovary Style
  24. 24. Ovary• swollen base of the pistil where ovules are formed Ovary
  25. 25. Pollination• Most gymnosperms and some angiosperms are wind pollinated, whereas most angiosperms are pollinated by animals• Insect pollination is beneficial to insects and other animals because it provides them with food• Plants also benefit because this method of pollination is more efficient
  26. 26. Q: What kind of symbioticrelationship is this?A: Mutualism
  27. 27. 25 – 1 Hormones and Plant Growth• In plants, the division, maturation, and development of cells are controlled by a group of chemicals called hormones
  28. 28. Hormones• A substance that is produced in one part of the organism and affects another part of the same organism
  29. 29. Target Cell• The portion of an organism affected by a particular hormone
  30. 30. Auxins• Discovered by Charles Darwin and his son• They were trying to explain phototropism
  31. 31. Phototropism• The tendency for plants to grow toward light
  32. 32. • Auxins are produced in the apical meristem and are transported downward into the rest of the plant• They stimulate cell elongation
  33. 33. Gravitropism• The response of a plant to gravity
  34. 34. Auxin Like Weed Killers• High concentrations of auxins can inhibit growth, so scientists have produced many auxin like compounds to be used as herbicide• Ex.) Agent Orange
  35. 35. Cytokins• Plant hormones that stimulate cell division, the growth of lateral buds and cause dormant seeds to sprout• Cytokins often produce effects opposite to those of auxins
  36. 36. Gibberellins• Promote growth, particularly in stems and fruits
  37. 37. Ethylene• Stimulate fruits to ripen
  38. 38. 25 – 2 Plant Responses
  39. 39. tropisms• The response of plants to external stimuli• Ex.) gravitropism and photoperiodism
  40. 40. Thigmotropism• Growth in response to touch
  41. 41. Rapid Responses• Some plant responses do not involve growth, they are so rapid it would be a mistake to call them tropisms• Ex.) sensitive plant, venus fly trap
  42. 42. Sensitive Plant
  43. 43. Venus Fly trap
  44. 44. Photoperiodism• The way a plant responds to periods of light and darkness• Short day plants – flower when days are short• Long day plants – flower when days are long• Photoperiodism in plants is responsible for the timing of seasonal activities of plants
  45. 45. Dormancy• The period during which an organism’s growth and activity decrease or stop• As cold weather approaches deciduous plants turn off photosynthetic pathways, transport materials from leaves to roots, and seal leaves from the rest of the plant

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