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Exploring Cycads: Ancient Plants of the Earth

Discover the fascinating world of cycads, ancient seed-bearing plants with unique characteristics. From their tropical distribution to reproductive structures, learn about cycad species like Dioon and Encephalartos. Explore the diverse vegetation of Cycads, including their distinct stems, leaves, and coralloid roots. Uncover how Cycads produce pollen and seeds in cones, and how they are pollinated by insects. Delve into the intriguing Gnetophytes like Ephedra, Gnetum, and Welwitschia, each with its own desert or tropical habitat. Lastly, uncover the Maidenhair Tree, Ginkgo biloba, renowned for its distinctive features and historical cultivation. Journey into the world of these unique plant species with this informative guide.

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Exploring Cycads: Ancient Plants of the Earth

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  1. 0 Seed-bearingPlants

  2. 0

  3. 0 Land Plants fall into two major groups • Non vascular • Vascular

  4. 0 Vascular Plants • Some are seedless • Others produce seed

  5. 0 Seed-bearing Vascular Plants fall into two major categories Angiosperms Gymnosperms

  6. 0 Seed-bearing Vascular Plants fall into two major categories • Gymnosperm – seeds naked on surface of sporophyll • Angiosperm – seeds enclosed in a ripened ovary

  7. 0 Seed-bearing plants also produce pollen

  8. 0 Living Gymnosperms Cycads Conifers Ginkgoes Gnetophytes

  9. 0 Cycads Appeared on Earth 250 MYA • Reached their greatest abundance and diversity during the Jurassic • Declined sharply during the Cretaceous radiation of the angiosperms.

  10. Global Distribution of Cycads is Tropical

  11. 0 Mexican Cycads Dioon Ceratozamia

  12. 0 Australian Cycads Macrozamia Macrozamia

  13. 0 African Cycads Encephalartos Stangeria

  14. 0 Only Cycad Native to the US Zamia pumila

  15. 0 Cycads – Vegetative Characteristics Encephalartos in Africa

  16. 0 Cycad Stems • Columnar • Little branching • Not very woody

  17. Produced in crowns at tip of stem Pinnately compound 0 Cycad Leaves

  18. 0 Certain roots in Cycads grow toward the soil surface Corraloid Roots

  19. 0 A Closer Look at Coralloid Roots • Grow upward near soil surface • Branch to form masses • Root cortex inhabited by Cyanobacteria(carry out nitrogen fixation)

  20. 0 Cycads – Reproductive Structures

  21. Cycads produce pollen and seeds in cones • Cones develop at apex of stem

  22. 0 All Cycads are Dioecious • Individual plants produce either pollen cones or seed cones Pollen Cone Seed Cone Cycas revoluta

  23. 0 Many Cycads are Pollinated by Insects • Only a few cycad species studied • Weevils and oldest known bee genus (Trigona) • Usually pollinators mate and lay eggs within female cone • All cones except Stangeria produce heat. Thought to volatilize pollinator attractants • Hence insect pollination may predate flowering plants Trigona weevils

  24. The Gnetophytes Ephedra Gnetum Welwitschia

  25. 0 Ephedra is a desert shrub

  26. Ephedra is distributed in arid regions of the world 50 species 39 species monotypic

  27. Ephedra contains Ephedrine http://www.anephedraattorneyforyou.com/

  28. Pseudoephedrine is a Synthetic Version of Ephedrine

  29. Gnetum is a tropical vine or small tree

  30. Gnetum occurs in the tropics 50 species 39 species monotypic

  31. Welwitschia is a bizarre plant of an extremely arid environment

  32. Welwitschia occurs only in the Namib Desert in South-West Africa 50 species 39 species monotypic

  33. Welwitschia forms a short stem and deep tap root

  34. Welwitschia produces only two adult leaves

  35. Welwitschia leaves grow from the base – leaves fray as they grow

  36. Ginkgo – The Maiden Hair Tree

  37. Today represented by a single species Once occurred in North American Forests Presently occurs naturally only in China 0 Ginkgo was a common forest tree in the geological past

  38. “Natural” trees may actually be plants cultivated at ancient Monasteries 0 Present Distribution of Ginkgo biloba

  39. Ginkgo is also widely cultivated

  40. 0 Ginkgo – Vegetative Characteristics

  41. Ginkgo is Deciduous

  42. Ginkgo is Deciduous

  43. Extensive branching Very woody 0 Ginkgo Stems

  44. 0 Ginkgo Stems long shoot spur shoot

  45. 0 Ginkgo Stems spur shoot long shoot

  46. Fan shaped Dichotomous branching veins 0 Ginkgo Leaves

  47. Leaf shape ranges from entire to bilobed

  48. Individual plants produce either pollen “cones” or seed “cones” Produced on spur shoots 0 All Ginkgo trees are Dioecious C Pollen “Cone” Seed “Cone”

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