The Wonderful World of Green Plant Diversity and

The Wonderful World of Green Plant Diversity and Evolution Biol 366 Spring 2014

Tree of Life: The Big Picture now Bacteria Archaea Eukaryotes >2 bya >3. 5 bya ca. 4 bya membrane-bound nucleus, organelles, etc.

Fig. 1. 1 from Simpson

Green plants share: • Chlorophylls a (ancestral) and b • Starch storage • Stellate flagellar structure • Certain gene transfers from the chloroplast to the nucleus • And other features (see Ch. 3)

Green plant diversity: • Ca. 350, 000 species • Two major groups: 1) chlorophytes (marine and other green algae) and 2) streptophytes [freshwater green algae and embryophytes (= land plants)] • A major branch (clade) in the eukaryotic Tree of Life

Fig. 3. 1 from Simpson

Some definitions • Clade = branch on an evolutionary tree, a lineage, includes an ancestor and all its descendants. Ex. : Green plants, chlorophytes, land plants. • Paraphyletic group = a group that includes an ancestor and some (but not all) of its descendants, indicated by double quotation marks. Ex. : “Green algae”

Chlorophytes

Fig. 3. 1 from Simpson

Spirogyra Chara Nitella (Judd et al. 2008) Basal streptophytes desmids

haploid body Conjugation in Spirogyra Haplontic life cycle (haploid dominant or zygotic meiosis) The only diploid cell Is the zygote (2 n)

biology. unm. edu ♀ Charales Haplontic but some have multicellular gametangia (gamete-producing structures) ♂ mason. gmu. edu

gametangia X X gametophyte Generalized charophyte life cycle: Alternation of generations

Embryophytes (land plants) share: • Cuticle • Alternation of generations (multicellular sporophyte and multicellular gametophyte) • Multicellular gametangia (gamete-producing structures) • Multicellular sporangium (spore-producing structure) • Embryo (young sporophyte) • Parenchyma? (more likely ancestral)

Generalized embryophyte life cycle: Alternation of generations

Bryophytes • Hornworts, liverworts, mosses • Gametophyte-dominant • No vascular tissue (except conducting cells in a few mosses) • Separate male and female gametophytes • Sperm must swim to the egg, therefore need water for fertilization and therefore must remain small

liverworts mosses hornworts

Plant Tree of Life: Embryophtes “Bryophytes” now Liverworts ca. 450 mya Hornworts Mosses Tracheophytes (vascular plants)

Liverwort gametophyte

Liverwort thallus showing air pores

Liverwort Multicellular gametangia (male = antheridia)

Liverwort Multicellular gametangia (female = archegonia) Oogamy Retention of zygote within the female gametophyte Multicellular embryo

G S Hornworts

Moss male gametangia (= antheridia) Capsule = sporangium of the sporophyte

Generalized embryophyte life cycle: Alternation of generations

Tracheophytes (vascular plants) • Vascular tissue (tracheids) present • Include lycophytes (quillworts, clubmosses, spikemosses), monilophytes (ferns, horsetails, whisk ferns), and spermatophytes (seed plants)

Fig. 4. 1 from Simpson

Lycophytes & Monilophytes • Quillworts, clubmosses & spikemosses (= lycophytes); ferns, whisk-ferns, & horsetails (= monilophytes); • Independent gametophytes and sporophytes • Sperm must still swim to the egg • Most are homosporous; a few evolved heterospory • Many homosporous ferns have means of avoiding self-fertilization

Lycophytes Isoetes (quillwort) Selaginella (spikemoss) Lycopodium and friends (clubmosses)

Monilophytes (ferns, horsetails, whisk ferns) horsetails Whisk-fern (Psilotum) Ferns (Leptosporangia)

Nutritionally independent sporophytes and 2 n gametophytes sporophyte 2 n gametophyte 1 n 1 n spores 2 n 2 n

Fern Life Cycle, Fig. 4. 32, Simpson

Lignophytes (woody plants) & Spermatophytes (seed plants) • Secondary xylem (wood) & bark, heterospory, seeds, eustele, pollen (also pollen tube, pollination droplet) • Includes gymnosperms and angiosperms

Fig. 5. 1 from Simpson

Gymnosperms • Conifers, gingko, cycads, Gnetales • Molecular data support this group as having a single common ancestor • No obvious defining character (see characters for Lignophytes & Spermatophytes)

Female cone with each scale bearing usually two ovules; directly exposed to pollen Male cones with each scale bearing two or more microsporangia

male pine pollen pine microsporangia biology. ualberta. edu female

Fig. 5. 7 from Simpson

Angiosperms • • • “Dicotyledons”, monocotyledons Heterosporous (ancestral) Sporophyte-dominant (ancestral) Pollen = male gametophyte (ancestral) Archegonia lost; embryo sac = female gametophyte; ovules enclosed in carpels (indirect pollination) • Double fertilization produces zygote + primary endosperm nucleus

Flower = a short, determinate shoot bearing highly modified leaves, some of which are fertile (i. e. , bearing either microsporangia or megasporangia), with the megasporangia in carpels

Animal pollination syndromes

Wind pollination

A wide range of fruit types…

Fig. 5. 7 from Simpson

http: //www. mun. ca/biology/scarr/Angiospermae. html

The wonderful world of land plant diversity over 300, 000 species of angiosperms