The Diversity of Plants

1. The Diversity of Plants

2. The huge, foul-smelling flower of the stinking corpse lily Parasite

3. What Is the Evolutionary Origin of Plants? • Photosynthetic protists • Probably similar to today’s algae • Lacked true roots, stems, leaves, and complex reproductive structures such as flowers or cones • Evolutionary tree of some major plant groups

4. Tracheophytes維管植物(vascular plants) Bryophytes苔蘚類(non-vasvular plants) seed plants Liverworts Mosses Ferns Gymnosperms Angiosperms 無種子維管束植物: 維管束植物中，有些植物不產生種子，如蕨類，它們會產生風媒孢子來散播。 • 維管束植物: 蕨類、裸子和被子植物都具有維管束，因此具有真正的根、莖和葉等構造。 • 維管束植物體內的維管束組織貫穿根、莖和葉等器官，使植物體內的水分和養分的輸送加快，並且可支持植物體，使其直立。因此，維管束植物長得比蘚苔植物高大。 • 種子植物: 裸子植物和被子植物靠種子繁殖 • 乾燥的種子不但可以長期保存，抵抗乾燥，而且在適宜環境下萌芽時，種子內儲藏的養分可以供給其內的胚發育，增加種子植物繁殖和擴張生長範圍的能力。 • 因此，種子植物在現今地球陸地上占了大部分的生長面積 無維管束植物: 僅蘚苔植物不具維管束(為輸導組織)，沒有真正的根、莖和葉等構造 Ancestral green alga

5. Green algae gave rise to plants • Green algae, closest living relatives • DNA comparisons • same type of chlorophyll and accessory pigments for photosynthesis • Food storage • starch • Cellulose cell walls • The ancestors of plants lived in fresh water • Highly variable • Temperature • Chemicals in water • Periods of dryness

6. Key Features of Plants • Multicellular • Photosynthetic • Plants are adapted to life on land • Alternating generations of diploid and haploid stage (reference)

7. MITOSIS gametophyte (n) MITOSIS sperm n n egg n n n n spores FERTILIZATION MEIOSIS spore mother cell 2n zygote 2n 2n embryo sporophyte (2n) Haploid Diploid haploid diploid

8. Environmental challenges of plants living on land • No supportive buoyancy of water • Not bathed in a nutrient solution • Air is a drying medium • Gametes and zygotes cannot be carried by water currents or propelled by flagella

9. Plant Bodies Resist Gravity and Drying • Roots/root-like structures – anchor and get water and nutrients; all land plants • Waxy cuticle – limits water loss; all land plants • Stomata: gas exchange and limit water loss; all land plants • Conducting vessels – transport water and mineral in the plant; vascular plants • Lignin – increases rigidity, thereby increasing sun exposure; vascular plants

10. Plant Embryos Are Protected and Plant Sex Cells May Disperse Without Water • Well-protected and well-provisioned embryos • Seeds • wind • Fruit • Animal forager and dispersed the indigestible seeds • Waterless dispersal of sex cells • Pollens • wind • Flowers • Animal pollinators

11. What Are the Major Groups of Plants?

12. Two major groups of land plants • Nonvascular plants (moss…) • Lack Conducting Structures • Requires a moist environment ot reproduce • Straddles the boundary between aquatic and terrestrial life • Vascular plants (ferns, gymnosperms, flower plants)

13. Non-vascular plants Bryophytes • Lack true roots, leaves, and stems • Rootlike anchoring structure--- rhizoids • Bring water and nutrients into the plant body • Lack well-developed structures for conducting water and nutrients • Nonvascular • Diffusion or poorly developed conducing tissues to distribute water and other nutrients • Body size is limited • No supporting tissues in their bodies • Body size is less than 1 inch (2.5cm)

14. Liverworts grow in moist, shaded areas. This female plant bears umbrella-like archegonia 造卵器, which hold the eggs. Sperm must swim up the stalks through a film of water to fertilize the eggs. 苔蘚類植物具有直立的假莖，其上著生假葉，並有假根固著在土壤內。

15. Moss plants, showing the stalks that carry spore-bearing capsules. 苔蘚類植物，植物體平鋪於地面上，腹部的假根則固著在土壤內，以吸收水分 Most mosses are confined to a wet environment -though some mosses have a waterproof covering that retains moisture preventing water loss and can survive in deserts (on bare rock) or in far northern and southern latitudes where humidity is low and water is scarce for much of the year

16. The leafy green gametophyte (lower right) is the haploid generation that produces sperm and eggs. emerging gametophyte Egg producing organ Sperm producing organ leafy gametophyte haploid diploid

17. capsules MEIOSIS emerging sporophyte capsules Sporophyte develops within gametophyte The sporophyte is topped by a brown capsule in which haploid spores are produced by meiosis. FERTILIZATION

18. capsules MEIOSIS emerging sporophyte capsules FERTILIZATION emerging gametophyte leafy gametophyte haploid diploid Life cycle of a moss haploid spores

19. Haploid Gametophyte stage of their alternation of generations is the most prominent phase

20. Bryophytes lack conducting structures • Rhizoids • Limited size – lack of vascular tissue and lignin • Sexual Reproductive structures (gametes) • a. Archegonia – produce eggs • b. Antheridia – produced swimming sperm • Gametophyte stage of their alternation of generations is the most prominent phase

21. Vascular plants • Vessels • A specialized groups of conducting cells • Allow water and nutrients absorbed by the roots to move to the upper portions of the plant • That are impregnated with the stiffening substance Lignin • adds extra support, • Vascular plants grow taller than nonvascular plants

22. 苔蘚類植物

23. The seedless vascular plants • include the ferns, club mosses, and horsetails • Produce swimming sperm, so water is essential for reproduction • Do not produce seeds, they propagate by spores • Diminished in size compared to their ancestors • Dominated the landscape hundreds of millions of years ago

24. The club mosses grow in temperate forests (few inches in height, ground pine) deer fern The giant horsetail (scouring rush)

25. Ferns • 1200 species • most diverse seedless vascular plants • Ferns are the only seedless vascular plants that have Broad leaves • Sporangia produce spores on specialleaves of sporophyte • Spores are dispersed by the wind • give rise to tiny, haploid gametophyte which produce sperm and eggs

26. Sexual reproduction in ferns • Retains two traits that are reminiscent of the bryophytes 1. a small independently living gamete production plant body (gametophytes) exists 2. as in bryophytes, the sperm must swim through water to reach the egg

27. haploid diploid sporophyte masses of sporangia sporangium leaf MEIOSIS stem root Haploid spores, formed in sporangia located on the underside of certain leaves, are dispersed by the wind to germinate on the moist forest floor into inconspicuous haploid gametophyte plants. The dominant plant body is the diploid sporophyte.

28. FERTILIZATION archegonium gametophyte sperm antheridium haploid sheetlike gametophytes, male antheridia and female archegonia produce sperm and eggs. The sperm must swim to the egg, which remains in the archegonium. The zygote develops into the large sporophyte plant. diploid

29. sporophyte masses of sporangia sporangium leaf MEIOSIS root stem FERTILIZATION gametophyte haploid diploid

31. The seed plants • dominate the land • Distinguished from bryophytes and seedless vascular plants by pollen and seeds • pollen • Pollen grains – tiny structures that carry sperm-producing cells • transport the sperm without water; dispersed by wind or animals • Seeds –consists of an embryonic plant, a supply of food for embryo, and protective coat • Seed coat – protects embryo and maintains dormancy • Stored food used by embryo until it does its own photosynthesis • Dispersed by wind, water, or animals

32. embryo stored food seed coat Pine seed (gymnosperm) Bean seed (angiosperm)

33. Gametophytes of seed plants • are microscopic • Female gametophyte is a small group of haploid cells • Male gametophyte is the pollen grain

34. Two major groups of seed plants • Gymnosperms ---- Lack flowers • Angiosperms ---- flowering plants

35. Gymnosperms • Are Non-flowering Seed Plants • Evolved earlier than the flowering plants • Conifer • 500 species • Pines, firs, spruce hemlocks and cypresses • Habitats: in the Cold latitudes of the Far north and At high elevations where conditions are dry

36. Three ways of conifers to adapt the cold and dry environment • 1.retain green leaves through out the year, enabling these plats to continue photosynthesizing and growing slowly • Evergreens • 2. leaves are covered with a thick waterproof surface that minimizes evaporation • 3. produce an antifreeze in their sap that enables them to continue transporting nutrients in below-freezing temperature • Give their fragrant piney scent

37. E. Gymnosperms 裸子植物are nonflowering seed plants • 1. Conifers – adapted to dry, cold conditions • b. Male cones produce pollen dispersed by the wind • c. Female cones produce female gametophytes that develop and produce eggs • c. Embryos are enclosed in (naked) seeds dispersed when the scales of the female cone open

38. Reproduction of conifers • The tree is the diploid sporophyte • Develops both male and female cones • Male cones are relatively small (2 cm or less) • Release clouds of pollen during the reproductive season and then disintegrate • Female cones consists of a series of woody scales • Within which diploid cells undergo meiosis to produce haploid female gametophytes then develop and produce egg cells

39. Life cycle of the pine scale of female cone male cone female cone ovule scale of male cone spore-forming cell mature sporophyte MEIOSIS MEIOSIS seedlings female gametophyte Male gametophyte (pollen) seed egg cell pollen Tube (14 months) embryo haploid FERTILIZATION diploid

40. Ginkgo biloba Ginkgos 銀杏probably the first modern-day seed plants to evolve And widespread during the Jurassic period (208 million yrs ago)

41. Cycads蘇鐵probably evolved from ferns 160 species in tropic and subtropic lands

42. Angiosperms /flowering plants • are modern flowering seed plants • Dominated Earth for more than 100 million yrs • Highly diverse : 230,000 species • Duckweed浮萍 • Eucalyptus tree尤加利樹 • Grass • Cactus • Rule over the plant kingdom

43. Flowers attract pollinators • Flower develop on the dominant sporophyte plant • May have evolved when gymnosperm ancestors formed an association with animals that carried their pollen from plant to plant • Less pollen produced

46. Life cycle of angiosperm • Flowers are the structures in which both male and female gametophytes are formed • Female gametophytes develop from an ovule in the ovary of a flower • Male gametophytes (pollen) are formed inside a structure called the anther • Pollen tubes transport sperm from the flower stigma to the egg in the ovary • Plant embryo enclosed in a seed formed from the ovule

47. seedling flower stigma anther mature sporophyte food source embryo ovule seed coat ovule spore-forming cell seed anther contains cells that form pollen each seed developed from one ovule MEIOSIS MEIOSIS

48. pollen grain stigma pollen (male gametophytes) pollen tube spore FERTILIZATION sperm nuclei haploid female gametophyte diploid egg cell

49. seedling flower stigma anther mature sporophyte food source embryo ovule seed coat ovule spore- forming cell seed anther contains cells that form pollen each seed developed from one ovule MEIOSIS MEIOSIS pollen grain stigma pollen (male gametophytes) pollen tube spore FERTILIZATION sperm nuclei haploid diploid female gametophyte egg cell

50. The ovary surrounding the seed matures into a fruit Help to disperse the seed Edibility seeds are undigested and dispersed Clinging to animal fur Form wings to fly in air seed pollen grain stigma pollen tube FERTILIZATION sperm nuclei female gametophyte egg cell Fruits encourage seed dispersal each seed developed from one ovule