Rosette cellulose-synthesizing complexes Found only in land plants and charophycean green algae Figure 29.2 Rosette cellulose-synthesizing complexes 30 nm

Three Clades are candidates for Plant Kingdom Red algae ANCESTRAL ALGA Chlorophytes Viridiplantae Charophytes Figure 29.4 Three possible “plant” kingdoms Streptophyta Embryophytes Plantae

Alternation of generations = Derived traits of land plants Land Plants Life Cycle Gamete from another plant Gametophyte (n) Mitosis Mitosis n n n n Spore Gamete MEIOSIS FERTILIZATION Zygote 2n Figure 29.5 Derived traits of land plants Mitosis Sporophyte (2n) Alternation of generations = Derived traits of land plants

Derived Traits of Land Plants Multicellular Dependent Embryos Maternal tissue Figure 29.5 Derived traits of land plants Wall ingrowths 10 µm Placental transfer cell (outlined in blue) Embryo (LM) and placental transfer cell (TEM) of Marchantia (a liverwort)

Sporophyte 2n Gametophyte n Spores Sporangium Longitudinal section of Derived Traits of Land Plants: Walled Spores Produced in Sporangia: Spores Sporangium Longitudinal section of Sphagnum sporangium (LM) Figure 29.5 Derived traits of land plants Sporophyte 2n Gametophyte n Sporophytes and sporangia of Sphagnum (a moss)

Archegonia and Antheridia of Marchantia (a liverwort) Derived Traits of Land Plants: Multicellular Gametangia - ‘sex organs’ Archegonium with egg Female gametophyte Antheridium with sperm Figure 29.5 Derived traits of land plants Male gametophyte Archegonia and Antheridia of Marchantia (a liverwort)

Derived Traits of Land Plants Apical Meristems - Allow for Growth in Length throughout Plant’s Lifetime. Apical meristem of shoot Developing leaves Apical meristems Figure 29.5 Derived traits of land plants Apical meristem of root Shoot Root 100 µm 100 µm Derived Traits of Land Plants

NonVascular and Vascular Plants Table 29.1

Highlights of Plant Evolution 1 Origin of land plants (about 475 mya) 2 Origin of vascular plants (about 420 mya) 3 Origin of extant seed plants (about 305 mya) Liverworts Nonvascular plants (bryophytes) Land plants ANCES- TRAL GREEN ALGA 1 Hornworts Mosses Lycophytes (club mosses, spike mosses, quillworts) Seedless vascular plants 2 Vascular plants Pterophytes (ferns, horsetails, whisk ferns) Figure 29.7 Highlights of plant evolution Gymnosperms 3 Seed plants Angiosperms 500 450 400 350 300 50 Millions of years ago (mya)

Life Cycle of a Bryophyte > Moss Gametophyte is the Dominant Generation Raindrop Sperm “Bud” Antheridia Male gametophyte (n) Key Haploid (n) Protonema (n) Diploid (2n) “Bud” Egg Spores Gametophore Archegonia Spore dispersal Female gametophyte (n) Rhizoid Peristome Sporangium FERTILIZATION Figure 29.8 The life cycle of a moss MEIOSIS (within archegonium) Seta Zygote (2n) Capsule (sporangium) Mature sporophytes Foot Embryo Archegonium Young sporophyte (2n) 2 mm Capsule with peristome (SEM) Female gametophytes

Bryophyte Structures Sporophyte Gametophore of female gametophyte Thallus Sporophyte Foot Seta Figure 29.9 Bryophyte diversity Capsule (sporangium) Marchantia polymorpha, a “thalloid” liverwort 500 µm Marchantia sporophyte (LM)

Annual nitrogen loss (kg/ha) Bryophytes / Moss may help retain Nitrogen in the soil, an Ecological Advantage RESULTS 6 5 4 Annual nitrogen loss (kg/ha) 3 2 Figure 29.10 Can bryophytes reduce the rate at which key nutrients are lost from soils? 1 With moss Without moss

Sphagnum, or peat moss: economic and archaeological significance (a) Peat being harvested from a peat bog. Figure 29.11 Sphagnum, or peat moss: a bryophyte with economic, ecological, and archaeological significance (b) “Tollund Man,” a bog mummy: The acidic, oxygen poor conditions can preserve bodies.

Life Cycle of a Seedless Vascular Plant - Fern Dominant Sporophyte Key Haploid (n) Diploid (2n) Spore (n) Antheridium Young gametophyte Spore dispersal MEIOSIS Sporangium Mature gametophyte (n) Sperm Archegonium Egg Mature sporophyte (2n) Sporangium New sporophyte Zygote (2n) FERTILIZATION Sorus Figure 29.13 The life cycle of a fern Gametophyte Fiddlehead

Hypotheses for Evolution of Leaves Overtopping growth Megaphyll Vascular tissue Sporangia Microphyll Other stems become re- duced and flattened. Webbing develops. Figure 29.14 Hypotheses for the evolution of leaves (a) Microphylls - single veined leaves (b) Megaphylls - branching leaf veins

Homosporous spore production Typically a bisexual gametophyte Eggs Sporangium on sporophyll Single type of spore Sperm Heterosporous spore production Megasporangium on megasporophyll Female gametophyte Megaspore Eggs Microsporangium on microsporophyll Microspore Male gametophyte Sperm

Seedless Vascular Plants Lycophytes (Phylum Lycophyta) 2.5 cm Isoetes gunnii, a quillwort Strobili (clusters of sporophylls) Selaginella apoda, a spike moss Figure 29.15 Seedless vascular plant diversity 1 cm Diphasiastrum tristachyum, a club moss

Seedless Vascular Plants Pterophytes (Phylum Pterophyta) Athyrium filix-femina, lady fern Equisetum arvense, field horsetail Psilotum nudum, a whisk fern Vegetative stem Strobilus on fertile stem Figure 29.15 Seedless vascular plant diversity 25 cm 1.5 cm 2.5 cm

Artist’s depiction of a Carboniferous forest based on fossil evidence Figure 29.16 Artist’s conception of a Carboniferous forest based on fossil evidence

Derived Traits of Plants Apical meristem of shoot Developing leaves Gametophyte Mitosis Mitosis n n n n Spore Gamete MEIOSIS FERTILIZATION 2n Zygote Mitosis Haploid Sporophyte Diploid 1 Alternation of generations 2 Apical meristems Archegonium with egg Antheridium with sperm Sporangium Spores 3 Multicellular gametangia 4 Walled spores in sporangia

You should now be able to: Describe four shared characteristics and four distinct characteristics between charophytes and land plants. Diagram and label the life cycle of a bryophyte Explain why most bryophytes grow close to the ground and are restricted to periodically moist environments. Describe three traits that characterize modern vascular plants and explain how these traits have contributed to success on land.

Explain how vascular plants differ from bryophytes. Distinguish between the following pairs of terms: homosporous and heterosporous. Diagram and label the life cycle of a seedless vascular plant.