Plant Diversity What is a Plant?
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Biology 1030 Winter 2009 Plant Diversity Chapter 29 (573-588) Chapter 30 (591-606) Scott circa 2009 What is a Plant? • Plants are characterized by multiple traits: – Autotrophic – Cell walls – Storage material is starch – Bodies made of three organ types – Haplodiplontic life cycle • – Two multicellular stages They have tissues which develop from apical meristems Scott circa 2009 1 Biology 1030 Winter 2009 Plant Phyla • ~300,000 species • 10 phyla exist • Three major groups – Bryophytes • Bryophyta – mosses – Seedless vascular plants • Pterophyta – ferns – Seed plants • Coniferophyta – conifers • Anthophyta – flowering plants Scott circa 2009 Phyla You Don’t Need to Know • You are not responsible to know these phyla – – – – – – Hepatophyta p p y Anthocerophyta Lycophyta Cycadophyta Ginkophyta Gnetophyta Scott circa 2009 2 Biology 1030 Winter 2009 Alternation of Generations • Two multicellular stages – Gametes (n) – Zygote Gametophyte Mitosis n n • Mitosis n Spore – Sporophyte • Meiosis Mitosis MEIOSIS n Gamete FERTILIZATION – Spores • Mitosis 2n – Gametophyte – Gametes Zygote Mitosis Sporophyte Scott circa 2009 Sporophytes • Multicellular, diploid – Grow from zygote – May have vascular tissue • Function – Sporangia (sporangium) Spores – Sporocytes Spores Sporangium Scott circa 2009 3 Biology 1030 Winter 2009 Gametophytes • Multicellular, haploid – Grow from spores – Never have vascular tissue • Function – Gametangia • Archegonia (female) • Antheridia (male) Eggs Sperm (inside) Scott circa 2009 Basic Plant Body • Three organs Apical bud ground • Below g 1. Roots • Above ground 2. Stems (shoots) 3. Leaves Shoot system Vegetative shoot Leaf St Stem • Vascular tissue • Waxy cuticle Root system Scott circa 2009 4 Biology 1030 Winter 2009 Evolution of Land Plants 1. 2. Green algae ancestor Non-vascular plants – 3 3. • Apparent trends – – – – Bryophytes V Vascular l plants l t – – Non-seed plants Seed plants True organs Dominant generation Dependency on water Size and complexity Liverworts GREEN ALGA 1 Hornworts Mosses Lycophytes (club mosses, spike mosses, quillworts) 2 Pterophytes (ferns, horsetails, whisk ferns) Gymnosperms 3 Angiosperms Scott circa 2009 500 450 400 350 300 Millions of years ago (mya) 50 0 Phylum Bryophyta • Perennial gametophyte – Protonema(ta) – Gametophores – Apical meristem • Dioecious gametophytes – Male & female – Gametangia on mature plants Scott circa 2009 5 Biology 1030 Winter 2009 Bryophyta Body Plans • Gametophyte – No xylem or phloem • Non-vascular • Impact on size – No true organs • Thin ‘leaves’ • Simple ‘stems’ • Small ‘rhizoids’ – No cuticle • Impact on environment = A thallus Scott circa 2009 Bryophyta Body Plans • Sporophyte – Dependent on the gametophyte • Grows on • Fed by – Foot – Seta – Sporangium • Homosporous Scott circa 2009 6 Biology 1030 Winter 2009 Moss Water Loss • All habitats • Desiccation can occur in many Scott circa 2009 Life on Dry Land • Evolution of specific structures: – Epidermal secretions • Cuticle – Transport tissue • Xylem & Phloem Vascular tissue Scott circa 2009 7 Biology 1030 Winter 2009 Vascular Plants • Sporophyte dominant – Long-lived Long lived – Most are perennial • Three true organs – Roots – Shoots – Leaves • Three tissue types • Three cell types – Ground – Dermal – Vascular – Parenchyma – Collenchyma – Sclerenchyma Scott circa 2009 Phylum Pterophyta • The ferns – Seedless vascular plants • Sporophyte dominant – Perennial – Independent gamteophyte Scott circa 2009 8 Biology 1030 Winter 2009 Pterophyta Body Plans • Short-lived gametophyte – Thallus • Prothallium emerges – Small, photosynthetic • Hormonal sex determination – Hermaphroditic gametophyte • Antheridiogen g – Male gametophyte Scott circa 2009 Pterophyta Body Plans • Long-lived sporophyte – True organs – Underground stem (= rhizome) – Compound leaves (fronds) • Fiddlehead – Roots • Shoot apical meristem • Root apical meristems Leaves Rhizome Roots Scott circa 2009 9 Biology 1030 Winter 2009 Pterophyta Body Plans • Sporangia on leaves – Sporophylls – Annulus – Sporocytes • Homospores • Clustered in sori (sorus) – Indusium Scott circa 2009 The Seed Plants • Heterosporous spore production – Megaspores – Microspores • Dioecious gametophytes – Very small – Dependent • Ovule develops into the seed – Fertilization • Pollen grain – Carries sperm Scott circa 2009 10 Biology 1030 Winter 2009 Reduced Gametophytes • Trend – • Retention in megasporangium – Protection Scott circa 2009 Ovules & Seeds • Gymnosperms • Sporophyte tissue – Integument I t t – Megasporangium • One megaspore • Megagametophyte – Microscopic – Archegonia • Fertilization – Nutritive tissue • Angiosperms Scott circa 2009 11 Biology 1030 Winter 2009 Pollen Grains • Sporophytes house gametophytes – Cross fertilization • Sperm transfer vessels – Not dependent on water • Male gametophytes – Incredibly reduced Scott circa 2009 Pollen Grains • Dispersal – Wind – Wind & animals • Pollination – Direct – Indirect • Pollen tube forms – Sperm transfer – Fertilization IN ovule Scott circa 2009 12 Biology 1030 Winter 2009 Phylum Coniferophyta • Gymnosperms (naked seeds) • Sporophyte dominant • Cones – Pollen cone – microsporangia • Microsporophylls – Ovulate cone – megasporangia • Megasprorphylls Scott circa 2009 Coniferophyta Body Plans • Sporophytes • Most are evergreens – Leaves L are simple i l needles dl – Thick cuticle • Very long lived Scott circa 2009 13 Biology 1030 Winter 2009 Coniferophyta Body Plans • Megagametophyte • Microscopic – 1000s of cells – 2-6 2 6 archegonia h i • Fully dependent • Nutrition source Scott circa 2009 Coniferophyta Body Plans • Microgametophyte • Microscopic – 4 cells – 1 tube t b cell ll – 2 prothallial cells – 1 generative cell • Exine – coat • Generative cell division – Produces 2 sperm Scott circa 2009 14 Biology 1030 Winter 2009 Coniferophyta Pollination • Sperm transfer – Advantages • Direct pollination – Can be a long process • Ovule forms a naked seed Scott circa 2009 Anthophyta • Angiosperms (enclosed seeds) • Sporophyte dominant • The flowering plants – Very successful group • Sporangia contained in a flower – Stamen – microsporangia – Carpel – megasporangia • Can be found in every environment Scott circa 2009 15 Biology 1030 Winter 2009 Anthophyta Body Plans • Sporophytes • Two major groups – Monocots M t – (Eu)dicots – Seed leaves Scott circa 2009 Sporophyte Body Plans • Embryos – Seed leaves • Leaf venation • Stem vascular tissue Scott circa 2009 16 Biology 1030 Winter 2009 Sporophyte Body Plans • Roots • Pollen grains • Flowers Scott circa 2009 Anthophyta Body Plans • Megagametophyte • Microscopic – 7 cells (8 nuclei) – – – – Prothallial P th lli l (antipodal) ( ti d l) Syngergids Egg Polar nuclei • No N archegonia h i Scott circa 2009 17 Biology 1030 Winter 2009 Anthophyta Body Plans • Microgametophyte • Microscopic – only 2 cells! – Tube T b cell ll – Generative cell • Exine – coat • 2 sperm cells – Double fertilization Scott circa 2009 Anthophyta Pollination • Sperm transfer – Advantages • Indirect pollination – Double fertilization • Seeds are enclosed in a fruit Pollen grain Stigma Pollen tube 2 sperm Style Ovary Ovule Micropyle Scott circa 2009 18 Biology 1030 Winter 2009 Fruit • Expanded flower parts Carpels Flower Ovary Stamen Sepal Ovule Stigma Ovule Carpel (fruitlet) Seed Stigma Ovary (in receptacle) Remains of stamens and styles Sepals Ovary y Stamen Seed Receptacle Scott circa 2009 19
