Lecture Ch. 29 Date _______ Plant Diversity I: The Colonization of Land

Plant Evolution bryophytes (mosses), pteridophytes (ferns), gymnosperms (pines and conifers); angiosperms (flowering plants) Plants: multicellular, eukaryotic, photosynthetic autotrophs Terrestrial colonization: Vascular tissue The seed The flower Nonvascular plants -Bryophytes Bryophytes differ from algae-have multicellular embryo attached to and nourished by parent plant. Vascular plants-have xylem and phloem Pteriodophtes-ferns called seedless plants-lack a seed stage

Nonvascular vs. Vascular plants Nonvascular-Bryophytes Vascular Pteridophytes Gymnosperms Angiosperms

Plant origins Charophytes: green algae (closest plant ancestor) Similarities: 1-Homologous chloroplasts: chlorophyll a & b 2- Biochemical similarity cellulose composition; peroxisomes 3- Cell division similarity mitosis; cytokinesis 4- Sperm similarity ultrastructure 5- Genetic relationship nuclear genes; rRNA Cellulose in cell walls found in many algae groups including dinoflagellates and brown algae Chlorophyll a and b found in euglenoids and some dinoflagellates. Only charophyte algae and land plants have the same enzyme in peroxisomes -function antiphotorespiration Cell division similarity in cell plate formation-phragmoplast which is an alignment of cyoskeletal elements and Golgi derived vesicles across the midline of the dividing cell.

Characteristics that separate plants from algae ancestors Apical meristems: localized regions of cell division Multicellular, dependent embryos (embryophytes) Alternation of generations Walled spores produced in sporangia Multicellular gametangia Apical meristem-localized regions of cell division at tips of shoots and roots. Multicellular plant embryos develop from zygotes retained within tissue of female parents. Parent provides nutrients for embryo uses placental transfer cells- analogous to mother -embryo (placental) in mammals. Embryophytes- land plants Sporangia are multicellular organs found on the sporophyte generation that produces the spores. Spore mother cell w/in sporangia goes through meiosis to make spores. Sporangia holds the spores until they are ready to be released. Multicellular gametangia- produces the gametes. Gametangia is found in the gametophyte body. Archegonia-female gametangia is vase-shaped organ that produces a single egg cell and retains the egg in base of organ. Antheridia-mlae gametangia produces the sperm.

Other terrestrial adaptations Cuticle Stomata Xylem and phloem Secondary compounds Adaptions for Water conservation-- cuticle and stomata Adaptions for water transport --xylem and phloem Secondary compounds-alkaloids, terpenes, tannins-have bitter tastes, strong odors or toxic effects Defend plants against herbivores Flavonoids absorb harmful UV radiation flavonoids

Bryophytes Mosses, liverworts, and hornworts 1st to exhibit the embryonic condition (male = antheridium; female = archegonium) Flagellated (water) sperm No vascular tissue (imbibe water) No lignin (short stature) Haploid gametophyte is the dominant generation

Protonema-mass of green filaments that develop from germinating spores. Rhizoids-root like structures Sporophytes remain attached to gametophyte body Usually photosynthetic when young. Depend on the parent gametophyte for nutrition. Transferred by placental nutritive cells

Mosses

Parts of a Moss Plant Sporangium-or capsule holds the spores on sporophyte body Seta- stalk or stem of sporophyte body Foot- obtains nutrients from gameotphyte body Calyptra- protective covering over immature capsule Peristome- upper part of capsule specialized for gradual spore Protonema-mass of green filaments that grow from germinating spore. Rhizoids-act as roots to anchor the gametophyte body.

Three variations on gametophyte/sporophyte relations Page 598 Bryophytes Sporophyte dependent on gametophyte Gametophyte-dominant life cycle, the dependent sporophyte is nourished by the gametophyte as it grows out of the archegonium

Pteridophytes: seedless vascular plants Ferns, club ‘moss’, horsetails True roots and leaves Roots have lignified vascular tissue Sporophyte-dominant life cycle Homosporous plants: a single type of spore…. Sporophyte---->Single type of spore ---->Bisexual gametophyte ---->Eggs; sperm (flagellated; damp locations) Carboniferous period plants

Pteridophytes P. 598 Large sporophyte and small independent gametophyte (fern) Sporophyte is dominant generation Gametophyte is small, photosynthetic and free-living (not dependent on the sporophyte for their nutrition.

Life Cycle of a Fern

Fern Frond