Plant Diversity I How Plants Colonized Land

1. Chapter 29 Plant Diversity IHow Plants Colonized Land

2. Land plants evolved from Charophytes (Chara) green algae 4 key traits plants share with Charophytes (Morphological and Biochemical Evidence): 1. Rose-shaped complexes for cellulose synthesis 2. Peroxisome enzymes 3. Structure of flagellated sperm 4. Formation of a phragmoplast Plants vs. Algae

3. 5 key traits in nearly all land plants but are absent in the charophytes: 1. apical meristems 2. multicellular dependent embryos 3. alternation of generations 4. walled spores produced in sporangia 5. multicellular gametangia females – archegonia & males – antheridia

4. Apical meristems Developing leaves Apical meristem of shoot Fig. 29-5e Apical meristem of root Shoot Root 100 µm 100 µm

5. Embryo Fig. 29-5b 2 µm Maternal tissue Wall ingrowths 10 µm Placental transfer cell (outlined in blue) Embryo (LM) and placental transfer cell (TEM) of Marchantia (a liverwort)

6. Gamete from another plant Gametophyte (n) Mitosis Mitosis n n n n Spore Gamete Fig. 29-5a MEIOSIS FERTILIZATION Zygote 2n Mitosis Sporophyte (2n) Alternation of generations

7. Spores Sporangium Fig. 29-5c Longitudinal section of Sphagnum sporangium (LM) Sporophyte Gametophyte Sporophytes and sporangia of Sphagnum (a moss)

8. Archegonium with egg Female gametophyte Fig. 29-5d Antheridium with sperm Male gametophyte Archegonia and antheridia of Marchantia (a liverwort)

9. Origin of land plants (about 475 mya) 1 Origin of vascular plants (about 420 mya) 2 Origin of extant seed plants (about 305 mya) 3 Liverworts Nonvascular plants (bryophytes) Land plants Fig. 29-7 Hornworts ANCES- TRAL GREEN ALGA 1 Mosses Lycophytes (club mosses, spike mosses, quillworts) Seedless vascular plants Vascular plants 2 Pterophytes (ferns, horsetails, whisk ferns) Gymnosperms 3 Seed plants Angiosperms 50 500 450 400 0 350 300 Millions of years ago (mya)

10. Characteristics of all land plants: • eukaryotic, multicellular, autotrophic • cell walls made mostly of cellulose • chlorophylls a & b • Domain Eukarya, Kingdom Plantae In many plants, additional terrestrial adaptations, such as vascular tissues and secondary compounds, also evolved.

11. Nonvascular plants 1. Represented by three phyla: a. phylum Hepatophyta – liverworts b. phylum Anthocerophyta – hornworts c. phylum Bryophyta - mosses Liverworts Hornworts Moss

12. Gametophore of female gametophyte Thallus Sporophyte Fig. 29-9a Foot Seta Capsule (sporangium) Marchantia polymorpha, a “thalloid” liverwort 500 µm Marchantia sporophyte (LM)

13. gametophyte - mass of green, branched, one-cell-thick filaments sporophytes are smaller; only present part of the time spores germinate in favorable habitats • The gametophyte is the dominant generation in the life cycle sporophyte sporophyte gametophyte gametophyte

14. Raindrop Sperm “Bud” Antheridia Male gametophyte (n) Key Haploid (n) Protonemata (n) Diploid (2n) Fig. 29-8 The life cycle of a moss. “Bud” Egg Gametophore Spores Archegonia Female gametophyte (n) Spore dispersal Rhizoid Peristome FERTILIZATION Sporangium (within archegonium) MEIOSIS Seta Zygote (2n) Capsule (sporangium) Mature sporophytes Foot Embryo Archegonium Young sporophyte (2n) 2 mm Female gametophytes Capsule with peristome (SEM)

15. 3. Bryophyte sporophytes disperse enormous numbers of spores • sporophytes remain attached to gametophyte throughout the lifetime • depends on the gametophyte for sugars, amino acids, minerals and water. • sporangium (site of meiosis and spore production) can generate over 50 million spores.

16. 4. Bryophytes provide many ecological and economic benefits • distributed worldwide • common and diverse in moist forests and wetlands • Some common in extreme environments (mountaintops, tundra, and deserts)

17. Sphagnum, a wetland moss, is especially abundant and widespread. forms extensive deposits of undecayed organic material, called peat Wet regions dominated by Sphagnum or peat moss are known as peat bogs

18. Fig. 29-11 (a) Peat being harvested (b) “Tollund Man,” a bog mummy

19. Bog People

20. THE ORIGIN OF VASCULAR PLANTS 1. Two conducting tissues of the vascular system A. Xylem – Dead tissue, water-conducting B. Phloem – Living tissue, food-transporting 2. Water-conducting cells are strengthened by lignin and provide structural support 3. Sporophyte generation is dominant in vascular plants.

21. Seedless vascular plants 4. Two modern phyla: a. phylum Lycophyta – club mosses b. phylum Pterophyta - ferns, whisk ferns, and horsetails Club moss Whisk fern Horsetail Fern

22. Lycophytes (Phylum Lycophyta) 2.5cm Isoetes gunnii, a quillwort Strobili (clusters of sporophylls) Fig. 29-15a Selaginella apoda, a spike moss 1cm Diphasiastrum tristachyum, a club moss

23. Pterophytes(Phylum Pterophyta) Fig. 29-15e Athyrium filix-femina, lady fern Psilotum nudum, a whisk fern Equisetum arvense, field horsetail Vegetative stem Strobilus on fertile stem 25 cm 1.5 cm 2.5 cm

24. 5. Most seedless vascular plants are homosporous, producing one type of spore that develops into a bisexual gametophyte • both archegonia (female sex organs) and antheridia (male sex organs) • Eg., ferns eggs Single type of spore Bisexual gametophyte sporophyte sperm

25. Key Haploid (n) Diploid (2n) Antheridium Spore (n) Young gametophyte Spore dispersal MEIOSIS Fig. 29-13 The life cycle of a fern. Sporangium Mature gametophyte (n) Sperm Archegonium Egg Mature sporophyte (2n) New sporophyte Sporangium Zygote (2n) FERTILIZATION Sorus Gametophyte Fiddlehead

26. 6. seedless vascular plants are most common in damp habitats 7. ferns produce clusters of sporangia, called sori, on the back of leaves

27. Seedless vascular plants formed vast “coal forests” during the Carboniferous period • These plants left not only living representatives and fossils, but also fossil fuel in the form of coal.