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Coniferophyta

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Coniferophyta

  1. 1. Coniferophyta http://www2.mcdaniel.edu/Biology/botf99/gynopsperms/conifers.html
  2. 2. General Considerations: <ul><li>The most widespread of the gymnosperms are the conifers: 50 genera and over 550 species. </li></ul><ul><li>They can be found world-wide under varying conditions. </li></ul><ul><li>In the Americas they dominate the forests of the US West and Canada, then drop down the eastern coast dominating in the early successional stages; they continue and dominate the coastal and dry sandy forests of the SE. </li></ul>
  3. 3. Continue… <ul><li>Typically they are found under what we would consider the less productive conditions of either long cold seasons, dry areas or nutrient deficient soils ( sandy, less mature soils of the west or acidic swampy mucks). </li></ul><ul><li>Their history extends back to the late Carboniferous ( 300 MYA) where their drought resistant features might have been critical during their evolution during the Permian when the earth turned cold and dry. </li></ul>
  4. 4. Leaf and Wood Structure <ul><li>Although pine trees come to mind for most, when referring to gymnosperms, not all gymnosperms have needles as we'll see later with the ginkgo and gnetums. </li></ul><ul><li>Those that do have needles hold onto them year round, and can do so because the trees have tracheids , (as opposed to the vessels of angiosperms), </li></ul>
  5. 5. Continue… <ul><li>long, slender cells with tapered, overlapping ends; </li></ul><ul><li>water moves upward from tracheid to tracheid through pit pairs, thus preventing large gas bubbles from forming and thus no cavitations during freezing/defrosting periods. Water can move through the plant with little seasonal disruption. </li></ul>
  6. 6. Continue…
  7. 7. Continue… Note in the images on the left: on right..the wood cut is parallel to the tracheids.. the &quot;dots&quot; are the contiguous pores. On the left is a cross-section cutting through the tracheids - to the left of the image are the thinner walled cells that form in the spring and to the right, the heavier walled cells laid in the summer when less water is available. The big 'hole' at about 2 o'clock is a resin canal.
  8. 8. Continue… <ul><li>Gymnosperm wood is generally softer than angiosperms because it has l ess lignification . In the summer, angiosperms wood has more cell walls that also contribute to its ability to withstand more of &quot;a beating&quot;. </li></ul><ul><li>Resin is the antimicrobial material that seals wounds from insects and protects the tree from being eaten due to its foul taste. It is also flammable and thus it turns over the nutrients faster and clears the underbrush so that it makes sure to have enough water available for survival by eliminating the competition. The gymnosperms do not burn due to their often 1 ft thick cork that is fire resistant and helps to insulate the phloem against freezing in the winter. Resin is made of turpentine + wax (rosin). </li></ul>
  9. 9. Continue… <ul><li>Majority of conifers retain their needles for anywhere from 2-5 years, with a total dropping of needles every 5 years. </li></ul><ul><li>The bristlecone variety of gymnosperms however is an exception to this rule as it can hold its needles for up to 40 years ( ?) ( answer they live under such lousy conditions.. dry and low nutrient they don't have the reserves to build up a new stock every few years.. </li></ul>
  10. 10. Needles <ul><li>thick cuticle covers the epidermis beneath which 1+ layers of hypodermis - thick walled cells. </li></ul><ul><li>The stomata are sunken </li></ul><ul><li>The mesophyll cells have projections to increase surface area and generally contain 2+ resin canals </li></ul>
  11. 11. Continue… <ul><li>1-2 vascular bundles are found in the center surrounded by transfusion tissue to conduct materials between vascular and mesophyll cells </li></ul><ul><li>there are dead tracheids in the middle to support the structure </li></ul><ul><li>the endodermis surrounds the vascular tissue preventing water loss. </li></ul>
  12. 12. Continue…
  13. 13. Life Cycle
  14. 14. GYMNOSPERMS VS. ANGIOSPERMS <ul><li>POLLINATION: </li></ul><ul><ul><li>Angiosperms rely on plants and animals-this helped with the evolution of flowers to entice the insects and animals to spread their pollen </li></ul></ul><ul><ul><li>Gymnosperms rely on wind as their main source of pollination, which leads to trees with very similar genotypes in a very concentrated area (think of dense pine forests) </li></ul></ul><ul><li>TIME FROM POLLINATION TO FERTILIZATION </li></ul><ul><ul><li>Angiosperms pollinate and fertilize almost simultaneously </li></ul></ul><ul><ul><li>Gymnosperms -pollen can often sit for a period of up to 15 months or more before fertilization occurs. The pollen grains sit within the cone for this time. </li></ul></ul>
  15. 15. Continue… <ul><li>DOUBLE FERTILIZATION </li></ul><ul><ul><li>Angiosperms- one sperm fertilizes the egg while the other combines to form an endosperm </li></ul></ul><ul><ul><li>Gymnosperms- No double fertilization </li></ul></ul><ul><li>FRUIT </li></ul><ul><ul><li>Angiosperms- produce fruit-evolve with mammals to entice animals to spread pollen </li></ul></ul><ul><ul><li>Gymnosperms- seeds without fruit </li></ul></ul>
  16. 16. Some Pictures Cluster of microsporangiate strobili of Pinus resinosa Longitudinal section through a microsporangiate cone of pine consisting of microsporophylls spirally arranged around the central axis bearing microsporophylls.
  17. 17. Continue…   Detail showing microsporangia on lower surface of microsporophylls of pine Longitudinal section of a megasporangiate cone of pine consisting of seed-scale complexes spirally arranged around a central axis.
  18. 18. Continue…
  19. 19. Continue…
  20. 20. Araucariaceae Agathis A. robusta
  21. 21. Agathis australis A robusta leaves DW
  22. 22. Bough ovulate cones DW Large trunk AF Ovulate cone AF
  23. 23. Continue… Young ovulate cone
  24. 24. Bark AF Habit DW Older bark AF
  25. 25. Trunk DW
  26. 26. Wollemia Adult juvinal foliage JP
  27. 27. Colony KH Female cone KH
  28. 28. Fossil detail KH
  29. 29. Collecting seeds Crown male cones
  30. 30. Fossil
  31. 31. Male cone
  32. 32. Araucaria Branches leaves
  33. 33. Older male cones DW
  34. 34. Trunk RK Young male cones DW
  35. 35. Mature tree DW Older ovulate cones AF
  36. 36. Young female cones DW
  37. 37. Young tree RK
  38. 38. A heterophylla Branch RK Microsporangiate cone AF
  39. 39. Tree AF Habit ovulate cones AF
  40. 40. Terminal ovulate cones AF Tree RK
  41. 41. A cunninghamii Female cones DW Trunk DW
  42. 42. Tree DW Vegetative branch DW
  43. 43. Araucaria bidwillii Bough DW
  44. 44. Needles DW
  45. 45. Seed scale complex AF
  46. 46. Young growth AF Lateral branches DW
  47. 47. Older branch with needles DW
  48. 48. Tree AF Young tree DW

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