Plants The Producers Photosynthesis Ecological classification • Produce the food (photosynthesis) • Condition the environment • Glucose for energy fuel, organic chemical • Create shelter monomers, structural polymers. and habitat • Oxygen for aerobic respiration. Ecological communities are often named for the dominant producers Photosynthetic bacteria Cyanobacteria — “blue-green algae” use chlorophyll Halophilic archaea — “purple bacteria” • Not all producers are plants use bacteriorhodopsin Photosynthetic Protists Plants Cells Phytoplankton [ecological classification] — earth’s dominant producers! • Diatoms • Dinoflagellates Heyer 1 Plants Plant Cells / Tissues / Organs Alternation of Generations in Plant Reproduction Alternation of Generations in the Green Algae (Chlorophyte) Ulva Changing definitions of the MITOSIS Kingdom Plantae MITOSIS MALE & FEMALE 1. Classical: everything photosynthetic FLAGELLATED ZOOSPORES (1N) / not an animal 2. Whitaker’s 5-kingdom model: all eukaryotic multicellular photosynthetic organisms 3. Phylogenetic: “land plants” — exclude the algae = Embryophyta: dependent embryo, meristem growth & differentiation, cuticle MITOSIS MALE & FEMALE FLAGELLATED GAMETES (1N) 4. Cladistic: Viridiplantae (“green plants”) — ZYGOTE (2N) embryophyta + chlorophyta (“green algae”) Changing definitions of the Kingdom Plantae Plants ? • Algae — green alga, brown alga, red alga ? • Bryophytes — mosses, liverworts, hornworts • Pteridophytes — ferns and horsetails — conifers and cycads • Gymnosperms • Angiosperms — flowering plants Embryophyta Viridiplantae Plantae (eukaryotic photoautotrophs) Heyer 2 Plants (Macro-)Algae — Aquatic Plants • Three Divisions (Phyla) Kelp Chlorophyta Life “Green Algae” Rhodophyta Cycle “Red Algae” Phaeophyta “Brown Algae” { including the “kelp” family } • Not directly related to each other, “Dependent embryo” nor to terrestrial vascular plants. — analogous to embryophytes • Accessory pigments allow greater light sensitivity at depth. Contrast between terrestrial vascular plant form and aquatic algal form. Bryophytes: Mosses • Land plants – Photosynthesis and gas exchange in leaves. – Nutrient and water uptake from soil by roots. – Vascular system transports between leaves & roots. – Woody tissues provide erect support. – Waxy cuticle resists drying. • Algae – Bathed in medium providing water, nutrients, and dissolved gases — roots, stomata, cuticle, and vascular • Haploid gametophytes are the dominant, conspicuous phase systems not needed – Photosynthesis occurs all over plant • Sperm “swim” to female gametophyte; require moist habitat body — no leaf specialization – Water environment provides • Spores may be dispersed by wind buoyancy / woody tissue not needed Vascular Plants (Tracheophytes) Pterophytes: Ferns Xylem - up! Phloem - down! • Diploid sporophyte is the dominant, conspicuous phase • Sperm “swim” to female gametophyte; require moist habitat • Spores are dispersed by wind Heyer 3 Plants Fern Life Cycle Fern frond x-sect w/ sorus http://www.flickr.com/photos/72616463@N00/4202468205/ Seed-bearing plants (Spermatophytes) Gametophytes & Sporophytes Two Clades: • The visible plant body is the diploid sporophyte • Gymnosperms “naked seeds” • The gametophytes are transient – Division: Conifers “cone microscopic structures bearers” – Female gametophyte within the ovule – Male gametophyte within the pollen grain • Pollen grains resist desiccation • Angiosperms “vessel seeds” — allow transport of sperm – Division: Anthophytes independent of water “flowering • After fertilization, ovule plants” develops into seed bearing the embryo Gymnosperms “naked seeds” Angiosperms — the flowering plants Conifers “cone bearers” >250,000 known living species = 90% of all plant species World’s largest biome: boreal coniferous forest [taiga] World’s largest organisms: sequoia & coast redwood Heyer 4 Plants Vascular Plants Xylem - up! Phloem - down! Vascular-plant structure Tracheophytes • 3 major tissue types 1. Vascular 2. Dermal 3. Ground Yet more surprising analogy between Rhizoids land plants and kelps • Non-vascular plants increase surface area • Dependent embryos for absorption & attachment with rhizoids • Meristematic growth • Differentiated tissues • Vascular tissue – Phloem-like sieve vessels • Trumpet-filaments joined by sieve plates in medulla Green algae Moss Fern prothallium cross section of a giant kelp stipe Non-vascular Rhizoids ! Vascular Root Roots • Taproot: from enlargement and Fern sporophyte branching of the seminal (seed) root. – Extends deeply – Starch storage • Fibrous root: thin roots originating from base of stem around seminal Fern prothallium root. – Dense network near soil surface • Adventitious root: fibrous-like roots rhizoids originating from additional stem nodes. – Extend fibrous root area – Asexual propagation – Prop roots root – Climbing anchors Heyer 5 Plants (dicot) Stele Gas exchange in vascular plants (vascular cylinder) • CO2 taken in and O2 given out by leaves for/from photosynthesis. • Dissolved O2 taken in with H2O from soil by roots for tissue (monocot) respiration. • During daylight: O2 out > O2 in • In dark of night: O2 out < O2 in Root Anatomy Leaves & Stems Leaves & Stems Alternate, simple leaves Opposite, compound leaves Leaf Anatomy Stomata — “little mouths” — adjustable openings for gas exchange on the undersides of leaves O2 bubbles forming from stomata Heyer 6 Plants Developmental Phase Changes of Meristem Two main classes of angiosperms: and • Monocots — grasses & grains (~70,000 spp.) Determinate Development of Leaves • Dicots —non-grasses (~180,000 spp.) Horizontal Stems • Stolon: above the surface • Rhizome: below the surface Adventitious Roots Vascular Bundles Vascular bundles of xylem & phloem Xylem - up! Phloem - down! in stem and leaf of monocot stem root Heyer 7 Plants Secondary xylem & Secondary xylem & phloem in plants phloem in woody plants Support (Dicot Angiosperms) Fibers (Dicot Angiosperms) [Gymnosperms are similar] [Gymnosperms are similar] Ray Secondary phloem Support Fibers Secondary xylem Ray Dialated phloem ray Annual growth rings in woody plants Seed-plant reproduction Spermatophytes Gymnosperm (“naked seed”) vs. Gymnosperms “naked seeds” Angiosperm (“vessel seed”) Conifers “cone bearers” Conifers: cones as sex organs • Seed develops from megasporangium: integument + nucellus with megasporocyte • In angiosperms, megasporangium develops within ovary (the “vessel”) Heyer 8 Plants Gymnosperm Gymnosperm Life Cycle Conifers: cones as sex organs • Sporophylls Conifers: • “spore leaves” with cones as sex organs • sporangia • Pollen cones [male] • Microsporophylls • Microsporangia • Microspores (n) • Ovulate cones [female] • Megasporophylls • Megasporangia • Megaspores (n) Gymnosperm Seed Development Angiosperms — the flowering plants Anthophytes: flowers as the sex organs • Non-reproductive perianth Style – Sepals form calyx – Petals form corolla • Male organ: Stamen – Filament & Anther – Anther produces pollen • Female organ: Carpel – Stigma, Style & Ovary – Stigma collects pollen Receptacle – Ovary produces ovules Reproductive Phase Changes of Meristem Angiosperm Gametophyte Development and Floristic Development • Meristem identity genes: leaf primordia → floral primordia • Organ identity genes: which floral primordia becomes which floral component – The ABC hypothesis Heyer 9 Plants Angiosperm Gametophyte Development Angiosperm Life Cycle Double Fertilization in Angiosperms Dicot- Angiosperm Seed Development Germinating pollen grains Angiosperm “vessel seeds” A fruit is a structure to protect and walls of ovary thicken to form fruit to carry the seeds disperse the embryos within the seeds More on fruits later! • Simple fruits develop from a single ovary of a single flower • Compound fruits develop from the fusion of many ovaries or many flowers Heyer 10 Plants Seed Development Seed Development Germination Sporophyte embryo: • Leaves [cotyledons] • Shoot [hypocotyl] • Root [radicle] Hypocotyl Avery GSJ (1933) Structure and germination of tobacco seed and the developmental anatomy of the seedling plant. American Journal of Botany 20: 309-327 Seed Development Monocots vs. Dicots Anthophyte Diversity (2) (1) Flowers & Fruits Flower Morphology Floral Anatomy regular / radial symmetry irregular / bilateral symmetry Heyer 11 Plants Flowers Flower Morphology and Ovary Position • Complete flower – calyx+corolla+stamens+carpels • Hermaphroditic: – Both male + female organs in same flower Hypogynous flower Perigynous flower Epigynous flower with superior ovary with superior ovary with inferior ovary • Monoecious: Lily [note non-green sepals!] – Separate male flowers & female • Hypogynous (flower “below ovary”): ovary positioned on the peak of the flowers on the same plant receptacle (torus). Other flower parts arise below the base of the carpels. E.g., Pea. • Perigynous (flower “around ovary”): ovary positioned in cup-like torus. Other • Dioecious: flower parts arise from edge of the cup. E.g., Rose. – Separate male flowers & female • Epigynous (flower “above ovary”): ovary completely embedded and fused within the receptacle. Other flower parts arise from the top of the ovary. E.g., Apple. flowers on separate plants Staminate Carpellate flower flower Begonias Bracts Inflorescence Multiple flowers (florets)) growing • Specialized leaves associated with as a distinct cluster flowers or cones • Most commonly with an inflorescence Protective bracts Bract convergence with flower parts • Petal-like bracts of poinsettias & bouganvillas Enclosing