1. Seedless Plants Chapter 30

2. Origin of Land Plants All green algae and the land plants shared a common ancestor a little over 1 BYA –Kingdom Viridiplantae –Not all photoautotrophs are plants Red and brown algae are excluded A single species of freshwater green algae gave rise to the entire terrestrial plant lineage 2

3. The green algae split into two major clades –Chlorophytes – Never made it to land –Charophytes – Sister to all land plants Land plants … –Have multicellular haploid and diploid stages –Trend toward more diploid embryo protection –Trend toward smaller haploid stage 3

4. 4 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Ancestral alga ChlorophytesCharophytesLiverwortsHornwortsMossesLycophytesGymnospermsAngiosperms Seed plants Euphyllophytes Bryophytes Land plants Streptophyta Green plants Green algae Red Algae Tracheophytes Ferns + Allies

5. Adaptations to terrestrial life –Protection from desiccation Waxy cuticle and stomata –Moving water using tracheids Tracheophytes have tracheids –Xylem and phloem to conduct water and food –Dealing with UV radiation caused mutations Shift to a dominant diploid generation –Haplodiplontic life cycle Mulitcellular haploid and diploid life stages Humans are diplontic 5

6. Haplodiplontic Life Cycle Multicellular diploid stage – sporophyte –Produces haploid spores by meiosis –Diploid spore mother cells (sporocytes) undergo meiosis in sporangia Produce 4 haploid spores First cells of gametophyte generation Multicellular haploid stage – gametophyte –Spores divide by mitosis –Produces gametes by mitosis –Gametes fuse to form diploid zygote First cell of next sporophyte generation 6

7. 7 Spore n n n n Spore mother cell 2n2n Sporangia Sporophyte (2n) 2n2n 2n2n Zygote Embryo Egg Sperm MEIOSIS MITOSIS FERTILIZATION n 2n2n Gametophyte (n)

8. All land plants are haplodiplontic Relative sizes of generations vary Moss –Large gametophyte –Small, dependent sporophyte Angiosperm –Small, dependent gametophyte –Large sporophyte 8

9. Bryophytes Closest living descendants of the first land plants Called nontracheophytes because they lack tracheids –Do have other conducting cells 9 Mycorrhizal associations important in enhancing water uptake –Symbiotic relationship between fungi and plants Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Charophytes Liverworts Mosses Hornworts Tracheophytes

10. Simple, but highly adapted to diverse terrestrial environments 24,700 species in 3 clades –Liverworts –Mosses –Hornworts Gametophyte – conspicuous and photosynthetic –Sporophytes – small and dependent Require water for sexual reproduction 10

11. 11 Liverworts (phylum Hepaticophyta) Have flattened gametophytes with liverlike lobes –80% look like mosses Form gametangia in umbrella-shaped structures Also undergo asexual reproduction Female gametophyte © David Sieren/Visuals Unlimited

12. Mosses (phylum Bryophyta) Gametophytes consist of small, leaflike structures around a stemlike axis –Not true leaves – no vascular tissue Anchored to substrate by rhizoids Multicellular gametangia form at the tips of gametophytes –Archegonia – Female gametangia –Antheridia – Male gametangia Flagellated sperm must swim in water 12

13. 13 Sporophyte Gametophyte Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. n 2n2n 2n2n 2n2n 1n1n 1n1n Sperm Sporangium Antheridia Egg Archegonia Gametophytes Spores Rhizoids Female Male Zygote MITOSIS FERTILIZATION Mature sporophyte Developing sporophyte in archegonium Parent gametophyte MITOSIS MIEIOSIS Germinating spores

14. Hornworts (phylum Anthocerotophyta) Origin is puzzling – no fossils until Cretaceous Sporophyte is photosynthetic Sporophyte embedded in gametophyte tissue Cells have a single large chloroplast 14 Photosynthetic sporophyte

15. Tracheophyte Plants Cooksonia, the first vascular land plant –Appeared about 420 MYA –Phylum Rhyniophyta Only a few centimeters tall –No roots or leaves –Homosporous – only 1 type of spore 15 Sporangia

16. Vascular tissues Xylem –Conducts water and dissolved minerals upward from the roots Phloem –Conducts sucrose and hormones throughout the plant Enable enhanced height and size in the tracheophytes Develops in sporophyte but not gametophyte Cuticle and stomata also found in land plants 16

17. Tracheophytes Vascular plants include seven extant phyla grouped in three clades 1.Lycophytes (club mosses) 2.Pterophytes (ferns, whisk ferns, and horsetails) 3.Seed plants Gametophyte has been reduced in size relative to the sporophyte during the evolution of tracheophytes Similar reduction in multicellular gametangia has occurred as well 17

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19. Stems –Early fossils reveal stems but no roots or leaves –Lack of roots limited early tracheophytes Roots –Provide transport and support –Lycophytes diverged before true roots appeared Leaves –Increase surface area for photosynthesis –Evolved twice Euphylls (true leaves) found in ferns and seed plants Lycophylls found in seed plants 19

20. 20 Euphyll Origins Lycophyll Origins Stem with vascular tissue Stem, leafy tissue without vascular tissue Stem, leafy tissue with vascular tissue Single vascular strand (vein) Branched vascular strands (veins) Photosynthetic tissue “webs” branches Branches in single planes Unequal branching Branching stems with vascular tissue

21. 400 million years between appearance of vascular tissue and true leaves –Natural selection favored plants with higher stomatal densities in low-CO 2 atmosphere –Higher stomatal densities favored larger leaves with a photosynthetic advantage that did not overheat Seeds –Highly resistant –Contain food supply for young plant –Lycophytes and pterophytes do not have seeds 21

22. Fruits in the flowering plants (angiosperms) add a layer of protection to seeds and attract animals that assist in seed dispersal, expanding the potential range of the species 22 Ancestral alga ChlorophytesCharophytesLiverwortsHornwortsMossesLycophytesGymnospermsAngiosperms Chlorophyll a and b Plasmodesmata Cuticle Antheridia and archegonia Multicellular embryo Stomata Euphylls Seeds Flowers Fruits Dominant sporophyte Stems, roots, leaves Ferns + Allies Vascular tissue

23. Lycophytes Worldwide distribution – abundant in tropics Lack seeds Superficially resemble true mosses Sporophyte dominant 23 HornwortsLycophytesSeed Plants Ferns and Allies

24. Princess Pine Dendrolycopodium obscurum 24

25. Shining Club Moss Lycopodium lucidulum 25

26. 26 Ground Pine

27. Pterophytes Phylogenetic relationships among ferns and their relatives is still being sorted out Common ancestor gave rise to 2 clades All form antheridia and archegonia All require free water for flagellated sperm 27 Lycophytes FernsHorsetail FernsFernsWhisk Ferns Seed Plants

28. Whisk ferns Found in tropics Sporophyte consists of evenly forking green stems without true leaves or roots Some gametophytes develop elements of vascular tissue –Only one known to do so 28

29. Horsetails All 15 living species are homosporous Constitute a single species, Equisetum Sporophyte consists of ribbed, jointed photosynthetic stems that arise from branching rhizomes with roots at nodes Silica deposits in cells – scouring rush 29

30. Ferns

31. Most abundant group of seedless vascular plants –About 11,000 species Coal formed from forests 300 MYA Conspicuous sporophyte and much smaller gametophyte are both photosynthetic 31

32. Fern life cycle differs from that of a moss Much greater development, independence, and dominance of the fern’s sporophyte Gametophyte lacks vascular tissue 32 MEIOSIS n 2n2n Archegonium Antheridium Egg Sperm Embryo 1n1n Gametophyte Rhizome Sporangium Spores Rhizoids Gametophyte MITOSIS Underside of leaf frond Mature sporangium Sorus (cluster of sporangia) Adult sporophyte Mature frond Leaf of young sporophyte MITOSIS Zygote 2n FERTILIZATION

33. Fern morphology –Sporophytes have rhizomes –Fronds (leaves) develop at the tip of the rhizome as tightly rolled-up coils (“fiddleheads”) 33 Tightly Coiled FernUncoiling Fern (left): © Mike Zens/Corbis; (right): © Ed Reschke Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

34. Fern reproduction Produce distinctive sporangia in clusters called sori on the back of the fronds Diploid spore mother cells in sporangia produce haploid spores by meiosis Spores germinate into gametophyte –Rhizoids but not true roots – no vascular tissue Flagellated sperm 34

42. rhizome fiddlehead/crozier sterile frond fertile frond

44. Ferns

50. Pinnate Pinnatifid

52. Not everything that looks like a fern is one!

53. …and not everything that is a fern looks like one!

54. 54 Ostrich Fern Matteuccia struthiopteris separate fertile and vegetative fronds

55. 55

56. 56 Sensitive Fern Onoclea sensibilis

57. 57 Hay-scented Fern Dennstaedtia punctilobula