Introduction to Plants

Figure 29.1 Figure 29.1 How did plants change the world?

Charophytes

Relationship between algae and land plants Red algae ANCESTRAL ALGA Chlorophytes Viridiplantae Figure 29.2 Three possible “plant” kingdoms Charophytes Streptophyta Plantae Embryophytes Figure 29.2

Green Algae & Plants: shared traits Chlorophyll A & B Cell walls of cellulos Starch as polysaccharide for storage

Charophytes as closest relatives Shared traits w/ land plants Protien rings on cell membrane to make cellulose Similar sperm (assymetrical arranged flagella) Phragmoplasts (microtubule arrangement during mitosis) Nuclear and chloroplast DNA similarities Some charophytes protect zygote w/ in gametophyte 30 nm

Derived Traits of Plants Five key traits appear in nearly all land plants but are absent in the charophytes Alternation of (heteromophic) generations Multicellular, dependent embryos Walled spores produced in sporangia Multicellular gametangia Apical meristems Cuticle Stomata (except liverworts)

Alternation of generations Figure 29.3a Alternation of generations Gametophyte (n) Gamete from another plant Mitosis Mitosis n n n n Spore Gamete MEIOSIS FERTILIZATION Zygote Figure 29.3a Exploring derived traits of land plants (part 1: alternation of generations) 2n Key Sporophyte (2n) Haploid (n) Mitosis Diploid (2n)

Multicellular, dependent embryos Figure 29.3b Multicellular, dependent embryos Embryo (LM) and placental transfer cell (TEM) of Marchantia (a liverwort) Embryo Maternal tissue Figure 29.3b Exploring derived traits of land plants (part 2: multicellular, dependent embryos) Wall ingrowths 2 µm 10 µm Placental transfer cell (blue outline)

Walled spores produced in sporangia Figure 29.3c Walled spores produced in sporangia Spores Sporangium Longitudinal section of Sphagnum sporangium (LM) Figure 29.3c Exploring derived traits of land plants (part 3: walled spores produced in sporangia) Sporophyte Gametophyte Sporophytes and sporangia of Sphagnum (a moss)

Multicellular gametangia Figure 29.3d Multicellular gametangia Female gametophyte Archegonia, each with an egg (yellow) Antheridia (brown), containing sperm Figure 29.3d Exploring derived traits of land plants (part 4: multicellular gametangia) Male gametophyte Archegonia and antheridia of Marchantia (a liverwort)

Apical meristems Apical meristem of shoot Developing leaves Figure 29.3e Apical meristems Apical meristem of shoot Developing leaves Apical meristem of root Figure 29.3e Exploring derived traits of land plants (part 5: apical meristems) Root Shoot 100 µm 100 µm Apical meristems of plant roots and shoots

- flowering plants (seed + flowers) Figure 29.5 Plant Diversity: - non-vascular - seedless vascular - seed (but no flowers) - flowering plants (seed + flowers) ANCESTRAL GREEN ALGA Liverworts Nonvascular plants (bryophytes) Origin of land plants Land plants 1 Mosses Hornworts Lycophytes (club mosses, spike mosses, quillworts) Seedless vascular plants Origin of vascular plants 2 Monilophytes (ferns, horsetails, whisk ferns) Vascular plants Figure 29.5 Highlights of plant evolution Gymnosperms Origin of extant seed plants Seed plants 3 Angiosperms 500 450 400 350 300 50 0 Millions of years ago (mya)

Table 29.1 Table 29.1 Ten phyla of extant plants

Challenges of dry land Dryness/relative lack of water Gravity (need for support)

Nonvascular plants (24,000 species) Liverworts, hornworts, & mosses

Nonvascular plants Gameptophyte dominant Dependent sporophyte Flagellated sperm Consequences on reproduction? Environment found? Non vascular tissue Size?

Protonemata (n) Zygote (2n) Mature sporophytes Figure 29.6 “Bud” Sperm Protonemata (n) Antheridia Key Male gametophyte (n) Haploid (n) Diploid (2n) “Bud” Egg Spores Gametophore Spore dispersal Archegonia Female gametophyte (n) Rhizoid Peristome Sporangium Seta FERTILIZATION Figure 29.6 The life cycle of a moss MEIOSIS Capsule (sporangium) (within archegonium) Zygote (2n) Mature sporophytes Foot Embryo Archegonium 2 mm Young sporophyte (2n) Capsule with peristome (LM) Female gametophyte

Animation: Moss Life Cycle

Capsule with peristome (LM) Figure 29.6a Figure 29.6a The life cycle of a moss (part 1: LM) 2 mm Capsule with peristome (LM)

(a) Peat being harvested from a peatland Figure 29.9 Figure 29.9 Sphagnum, or peat moss: a bryophyte with economic, ecological, and archaeological significance (a) Peat being harvested from a peatland (b) “Tollund Man,” a bog mummy dating from 405–100 B.C.E.

Seedless Vascular Plants Ferns, club mosses, horsetails, wiskferns, etc.. Monilophytes (Phylum Monilophyta) Strobilus on fertile stem Vegetative stem 3 cm 25 cm 4 cm Athyrium filix-femina, lady fern Equisetum telmateia, giant horsetail Psilotum nudum, a whisk fern

Seedless Vascular Plants: Lycophytes (Phylum Lycophyta) Figure 29.13a Seedless Vascular Plants: Lycophytes (Phylum Lycophyta) 2.5 cm Strobili (clusters of sporophylls) Isoetes gunnii, a quillwort Selaginella moellendorffii, a spike moss Figure 29.13a Exploring seedless vascular plant diversity (part 1: lycophytes) 1 cm Diphasiastrum tristachyum, a club moss

Seedless Vascular Plants Sprophyte dominant Independent gametophyte Flagellated sperm Impact on reproduction Vascular Tissue Transport Support Promotes increase in size

Vascular Tissue Xylem Phloem Transports water and minerals (nutrients from soil) Provides support Phloem Transports sugars

True roots, stems, & leaves Length via apical meristem Contain vascular tissues Anchor and absorb Leaves Specialized for photosynthesis Microphylls—single vein (of vascular tissue) Megaphylls—multiple veins (of vascular tissue) Sporophylls—leaves that create/house sporangia

Figure 29.14 Horsetail Fern Figure 29.14 Artist’s conception of a Carboniferous forest based on fossil evidence

Seed plants: gymnosperms + angiosperms

Seed plant developments Pollen Distribution (w/o water) and protection of sperm Non-flagellated sperm Ovule = megasporangium Contains egg Retained w/ in parent tissue After fertilization develops into seed

Seed From ovule Contains embryo (young sporophyte) Nutrients for embryo Protects and disperses embryo Important food source for animals, supported evolution of faster, larger, more intelligent organisms.

Figure 30.3-3 Immature ovulate cone Integument (2n) Female gametophyte (n) Seed coat Megaspore (n) Spore wall Egg nucleus (n) Spore wall Food supply (n) Discharged sperm nucleus (n) Megasporangium (2n) Figure 30.3-3 From ovule to seed in a gymnosperm (step 3) Pollen grain (n) Male gametophyte (n) Pollen tube Embryo (2n) Micropyle (a) Unfertilized ovule (b) Fertilized ovule (c) Gymnosperm seed

Figure 30.UN05 Five Derived Traits of Seed Plants Reduced gametophytes Microscopic male and female gametophytes (n) are nourished and protected by the sporophyte (2n) Male gametophyte Female gametophyte Heterospory Microspore (gives rise to a male gametophyte) Megaspore (gives rise to a female gametophyte) Ovules Integument (2n) Ovule (gymnosperm) Megaspore (n) Megasporangium (2n) Figure 30.UN05 Summary of key concepts: seed plant traits Pollen Pollen grains make water unnecessary for fertilization Seeds Seeds: survive better than unprotected spores, can be transported long distances Seed coat Food supply Embryo

Flowering Plants (angiosperms) Figure 30.17db Exploring angiosperm diversity (part 4b: eudicots) Dog rose (Rosa canina), a wild rose

Angiosperm developments Flowers Promote effective, targeted reproduction Transfer of sperm to egg Attract w/ sight and smell Reward w/ food (pollen and/or nectar) Fruit Protects and disperses seed more effectively

Tomato Ruby grapefruit Nectarine Hazelnut Milkweed ▼ ▼ ▼ ▼ ▼ Figure 30.10 Some variations in fruit structure ▼ Milkweed

Figure 30.11c The barbs of cockleburs facilitate Figure 30.11c Fruit adaptations that enhance seed dispersal (part 3: berries and other edible fruits) Seeds within berries and other edible fruits are often dispersed in animal feces. The barbs of cockleburs facilitate seed dispersal by allowing the fruits to “hitchhike” on animals. Figure 30.11c

Angiosperm Diversity: monocots v. dicots Embryos Leaf venation Stems Roots Pollen Flowers Monocot Characteristics Root system usually fibrous (no main root) Floral organs usually in multiples of three One cotyledon Veins usually parallel Vascular tissue scattered Pollen grain with one opening Eudicot Characteristics Figure 30.16 Characteristics of monocots and eudicots Vascular tissue usually arranged in ring Floral organs usually in multiples of four or five Two cotyledons Veins usually netlike Taproot (main root) usually present Pollen grain with three openings

Figure 30.2 PLANT GROUP Ferns and other seedless vascular plants Mosses and other nonvascular plants Seed plants (gymnosperms and angiosperms) Reduced, Independent (photosynthetic and free-living) Reduced (usually microscopic), dependent on surrounding sporophyte tissue for nutrition Gametophyte Dominant Reduced, dependent on gametophyte for nutrition Sporophyte Dominant Dominant Gymnosperm Angiosperm Sporophyte (2n) Microscopic female gametophytes (n) inside ovulate cone Microscopic female gametophytes (n) inside these parts of flowers Sporophyte (2n) Gametophyte (n) Microscopic male gametophytes (n) inside these parts of flowers Example Figure 30.2 Gametophyte-sporophyte relationships in different plant groups Microscopic male gametophytes (n) inside pollen cone Sporophyte (2n) Sporophyte (2n) Gametophyte (n)