General Biology/Classification of Living Things/Eukaryotes/Plants

Multicellular Photosynthetic Autotrophs Plants Multicellular Cellulose cell walls Chlorophylls a and b Develop from embryophyte Alternation of generations Major food source for terrestrial life Atmospheric O2 and CO2 balance Coal deposits Intimate association with mycorrhizal fungi >250,000 species (~500,000?) Taxonomy State of flux DNA sequencing Developmental studies Division (old literature) = phylum (new literature) ~12 phyla, 9 of which are vascular plants Plant phyla Phyla are 12 groupings Plant evolution Evolved from green algae, likely related to charophytes Evidence DNA sequences homologous chloroplasts: chlorophyll b and beta-carotene; thylakoids in grana; Cellulose in both groups; also peroxisomes Mitosis and cytokinesis similar Sperm ultrastructure Terrestrial adaptations Stomata: pores in leaves for exchange of gases; prevent desiccation Secondary metabolites: cuticle: waxy coating to prevent H2O loss lignin: hardens wood sporopollenin: resistant polymer; coats pollen predator defenses Embryonic development gametangia in early plants spores; seeds Mycorrhizae Water/food conducting systems Plant phylogeny Plant life cycles Alternation of generations Sporophyte diploid produces spores in sporangia Gametophyte develops from spore haploid produces gametes in gametangia Haplodiplontic life cycle Moss life cycle Moss has no vascular tissues or flowers. It is a thallus plant (it does not have true roots,stem and leaves). It does not produce seeds like the angiosperm. Vascular plants Most have roots Aerial shoot systems Vascular tissue xylem: water, mineral transport phloem: food transport Lignin Branched sporophyte is dominant stage amplified production of spores evolution of complex plant bodies Dominated Carboniferous (360 my) Vascular plant life cycles Homosporous (single type of spore) Heterosporous (two types of spore) Pterophyta (ferns) Non-seed plant Sporophyte conspicuous (vascular tissue) Rhizome: ground stem, roots Fronds: leaves Sori: clusters of sporangia Motile sperm require external water for fertilization Originated in Devonian, 350 my Tree fern Fern life cycle Non-seed plants, continued Lycophyta: club mosses E.g., Lycopodium (“ground pine”) Many species became extinct 270 my, once dominant (coal formations) Gametophyte non-photosynthetic, nourished by fungi Arthrophyta: horsetails Equisitum Some fossil forms (300 my) were tree-size (coal) Photosynthetic stems, no leaves Silica deposits in epidermal cells Seed plants 1st appeared in Devonian, 360 my Seed develops from ovule, protects embryo withstands drought dispersal is enhanced no immediate need for water for germination Heterosporous male gametophyte: arise from microspores female gametophyte: arise from megaspores in ovule in ovary Two groups gymnosperms angiosperms plant Sporophyte/gametophyte Megasporangium (nucellus) Key to seed development Nucellus: solid, fleshy, surrounded by integuments derived from sporophyte (seed coat) Entire structure called ovule Flower may have many ovules Pollen Develop from microspores, become male gametophyte Protected by sporopellenin In most plants, sperm lack flagella (loss) Many mechanisms to transport pollen wind insects, birds, Gymnosperms “naked seed” ovule not fully enclosed by sporophyte at time of pollination Conifers, cycads, gnetophytes, Ginkgo Small, inconspicuous plants to giants like sequoia Conifers: to carry cones fv male cones, Female conesvv evergreen Pine life cycle Other Coniferophyta Cycadophyta: cycads tropical, subtropical flagellated sperm Gnetophyta e.g., Ephedra, Mormon Tea Ginkgophyta: Ginkgo only one surviving species diecious (separate % and &trees) Other gymnosperms Angiosperms Flowering plants, Anthophyta monocots- single seed leaf (grasses, lilies, etc.) dicots- two seed leaves (roses, pulses, maples) More specialized xylem (water transport) vessel elements fiber cells Fossils date to 130 my Animal (e.g., insect) coevolution Monocots vs dicots Earliest angiosperm What is earliest angiosperm? Recent analysis of nucleotide and amino acid sequences suggests that Amborella, a tropical plant found only on the island of New Caledonia, is closest relative to flowering plants Angiosperm flower Angiosperm life cycle This text is based on notes very generously donated by Paul Doerder, Ph.D., of the Cleveland State University.