WORLD’S #1 ACADEMIC OUTLINE BarCharts, Inc.® • Study of the Plant Kingdom Our Essential Partners in Life • ALTERNATION OF GENERATIONS INTRODUCTION What’s so special about plants? • They are photosynthetic, using the ultimate energy source, the sun, to make their own food For this reason they are called autotrophs Plants power most ecosystems and are thus essential to life on Earth Have you thanked a plant today? GAMETE EVOLUTION Plants have developed different strategies for gamete production and fusion • Isogamy – Gametes are equally motile and of similar size • Anisogamy – One gamete Female(+) Male(-) is large and less motile, with nutrient reserves, while the other is smaller and more motile, with few nutrient reserves • Oogamy – One gamete is non-motile and large, with large nutrient reserves (egg), while the other is smaller and motile (sperm) and must locate the larger gamete Isogamy A unique evolutionary strategy for reproduction where a single plant organism has two phases to its life history • Gametophyte – Haploid, multicelled individual produces gametes via mitosis Dominant form in lower plants • Sporophyte – Diploid, multicelled individual from gamete fusion (zygote); produce haploid spores via meiosis for dispersal; spores germinate via mitosis to produce gametophytes Dominant form in higher plants • Isomorphic A/G – Gametophyte and sporophyte individuals are morphologically indistinguishable • Heteromorphic A/G – Gametophyte and sporophyte individuals are morphologically distinct PLANT CLASSIFICATION SEEDS, VASCULAR Angiosperms Oogamy Gymnosperms PLANT EVOLUTION • New problems on land: Plants must adapt to living in the air, a non-aquatic, dry medium This presents some problems: - Obtaining water and preventing water loss - Transporting water and nutrients - Gas exchange (requires moisture) - Gravity - Reproduction when gametes swimming in water is limited - Temperature flux of air is more rapid than in water Plant adaptations/solutions • Chlorophyll A & B, to capture sunlight – similar to green algae chlorophyll • Starch storage, for prolonged inactive periods during seasonal variations • Gametes protected and kept moist inside plant tissues • Stomata (leaf openings) to regulate gas exchange • Wax surfaces to prevent excess water loss • Root system to pull in water and nutrients from soil • Conduction tissues to transport water, nutrients and food • Support tissues to battle gravity for vertical growth • All of these adaptations have greatly enhanced the success of plants on land today Spore n n n Antheridium Archegonium Sperm Egg n Spores Syngamy Meiosis 2n 2n Spore mother cell Zygote 2n Embryo Sporangia Diploid Sporophyte (2n) NONVASCULAR PLANTS 1st Plants on Land • Lack vascular tissues • Gametophyte is dominant, sporophyte nutritionally dependent on gametophyte • Small; live in moist environments; gametes released into water a Division Hepatophyta (Liverworts) b Division Anthocerophyta (Hornworts) c Division Bryophyta (Mosses) Anisogamy Plant evolution: Land colonization occurred about 400 mya, likely from aquatic, green algae ancestor Haploid Gametophyte (n) (a) (b) SEEDLESS, VASCULAR Ferns Club Mosses Sporophyte Gametophyte Horsetails Growing region Foot of sporophyte Whisk Ferns (c) Capsule NONVASCULAR Sporophyte Mosses Seta Foot Liverworts Hornworts GREEN ALGAL ANCESTOR Gametophyte SEEDLESS VASCULAR PLANTS SEED “Ferns” Microphyll Evolution Stem Microphyll Vascular tissue Vascular Projection supply to projection Unbranched stem Leaf with one vein Extinct fossil forms that may show transition from seedless vascular plants (e.g., ferns) to vascular seed plants (e.g., gymnosperms and angiosperms) Megaphyll Evolution FLOWERS Main axis of stem Dichotomously branching stems Side branch Overtopping (one branch becomes main axis of stem) Megaphylls Leaves with many veins Webbing of side branch systems • Most plants are angiosperms and thus produce flowers with both male and female reproductive structures • Flower anatomy - Sepals, petals - Stamen (Male Portion): Anther, filament - Pistil (Carpel, Female Portion): Stigma, style, ovary, ovule { The pistil contains the female organs Stigma Style Ovary Ovule Petal { Seedless Vascular plants • Possess xylem & phloem for transport of materials • Sporophyte is dominant • Evolution of leaf for efficient light capture - Microphylls, megaphylls (In botany, the prefixes "micro" and "mega" generally refer to similar structures in male and female parts of the plant, respectively) • Division Lycophyta (Club Mosses) - Roots present - Leaves present (microphylls) • Division Psilophyta (Whisk Ferns) No roots or leaves • Division Sphenophyta ( Horsetails) - Roots present - Stems contain silica - Leaves present (microphylls) - Division Pterophyta (Ferns) - Roots present - Leaves (= fronds) - Fronds present (megaphylls) - Fern life history (see fig below) - Sporophyte, sori, sporangia, spores, gametophyte (= prothallus), archegonium with eggs and antheridium with sperm • The Plant Scene (300 mya): Many seedless vascular plants and some nonvascular plants exhibited lush, dense growth covering large expanses in Earth’s history • Much of today’s oil, coal and gas deposits were formed by these plants Evolution of the "seed" plants • Terrestrial adaptations of seed plants - Gametophytes protected in moist sporophytic, reproductive tissues - Pollination replaced swimming for sperm delivery to egg - The seed evolved - a dormant embryo with surrounding nutrients protected from environmental conditions Seeds replaced spores as dispersal agents, using wind, water or animals • The seed - a fertilized egg - Inside an ovule - Integument, megasporangium ➔ megaspore ‘gametophyte ➔ egg sperm Anthers (microsporangia) The stamen contains the male organs OVULE TO SEED Megasporangium (2n) Seed coat (2n) (derived from integument) Integument (2n) Spore case (n) Female gametophyte (n) Pollen tube (n) Egg nucleus (n) Micropyle Food supply (derived from female gametophyte tissue) Discharged sperm nucleus (n) Embryo (2n) (new sporophyte) Megaspore (n) (b) Fertilized ovule (a) Ovule Filament Sepal Receptacle (c) Seed FERN LIFE HISTORY The sporophyte (still attached to the gametophyte) grows, develops rhizome zygote sorus Diploid Stage fertilization Archegonium egg egg producing structure sperm sperm producing structure meiosis Haploid Stage Sporangia The spores are released from a spore chamber Spores develop Prothallus mature gametophyte (underside) A spore germinates and grows into a gametophyte Antheridium TRENDS IN ALTERNATION OF GENERATIONS Gametophyte (n) Sporophyte (2n) Gametophyte (n) Sporophyte (2n) Sporophyte (2n) • Sporophyte dependent on gametophyte (e.g., bryophytes) Gametophyte (n) • Large sporophyte and small, independent gametophyte (e.g., ferns) • Reduced gametophyte dependent on sporophyte (seed plants) • Angiosperms have dominated the plant scene since the demise of dinosaurs and many gymnosperms (Cenozoic era, 65 mya to present) • Seed in a protective container or cotyledon • Angiosperm life cycle: - Microspore mother cell ➔ microspores ➔ pollen grain (male gametophyte)which includes tube cell and generative cell (sperm) - Megaspore mother cell ➔ megaspore ➔ embryo sac with cells and nuclei (female gametophyte) ➔ egg - Two sperm move through the pollen tube and engage in a double fertilization (where one sperm fuses with the egg to form a zygote/embryo, and the other sperm fuses with a large, central cell to form endosperm/nutrient reserve for the embryo) until it can produce its first leaves and begin photosynthesis - Pollination and fertilization occur within hours to days, making angiosperms quick reproducers, compared to gymnosperms • Flowers ensure pollination by insects, birds and mammals - Flowers and pollinators co-evolved • Seed dispersal - Important because plants may drop seeds close by, but new individuals will possibly compete with parent plants - Wind, water and animals are common dispersal agents - Fruits can entice animals to aid in dispersal • Fruits – ripened ovary (see fig.) • Monocots and Dicots - two major groups of angiosperms (see fig for differences) - Monocots include grasses, corn, sugar cane, palm trees, lilies and orchids - Dicots include most trees, vines, shrubs and cacti THE GYMNOSPERMS - “naked seed” plants • Dominant plant when dinosuars ruled (Mesozoic era, 220 - 65 mya) • Do not produce flowers • Ovules/seeds exposed • Division Cycadophyta - Slow-growing palm-like trees found primarily in tropics and sub-tropics • Division Ginkgophyta - Only one living member - Ginkgo biloba (common diet supplement) • Division Gnetophyta - Closest living relatives of angiosperms - Ephedra - Drug ephedrine originally derived from this plant - Cells resemble xylem vessel cells of angiosperms - Cone clusters resemble flowers • Division Coniferophyta (Conifers, Evergreens) - Oldest, tallest, most massive plants (e.g., 380 ft tall Redwood tree) - Leaves form needles, which slow desiccation and are resistant to grazing by herbivores - Important economically as wood/paper source, resin, turpentine and Christmas trees • Pine life cycle: - Ovulate cone = megastrobilus with megasporophylls (scales) - Micropyle, where pollen lands on ovulate cone - Pollen cone = microstrobilus with microsporphylls - The process from pollination to fertilization can take over a year, which proved slow once the angiosperms evolved GYMNOSPERM LIFE CYCLE Megaspore(n) Scale of female cone Female cone HAPLOID Gametophyte generation Megasporangium Ovule Male cones Pollen chamber Note that the same plant has both pollen-producing male cones and egg-producing female cones Micropyle Female MEIOSIS gametophyte(n) Egg Microspores(n) Microspore Reduced mother cells(2n) archegonium Germinating pollen produces pollen tubes to reach the egg Male gametophyte (germinating pollen grain) Pollen grain FERTILIZATION Scale of male cone Sporophyte(2n) The gametophytes are tiny DIPLOID Sporophyte generation Female gametophyte(n) Seed coat Suspensors Seed Female gametophyte Zygotes(2n) Winged seed Embryo Female cone Developing embryo Wing The seed protects the embryo Scale of female cone THE ANGIOSPERMS - “enclosed seed” plants FRUIT DEVELOPMENT Endosperm ANGIOSPERM LIFE CYCLE Primary endosperm cell Pollen grains (n) Generative cell Anther Fruit flesh Ovary Meiosis Integument Seed coat Tube cell Fruit Microspores (n) Anther Pollen mother cells (2n) Stigma Functional megaspore (n) Megaspore mother cell (2n) Pollen tube 8-nucleate embryo sac (megagametophyte) (n) Zygote Embryo MONOCOTS VS DICOTS MONOCOTS DICOTS Sperm cells Florals parts in multiples of of Floral parts in multiples of three Meiosis Ovary Adult sporophyte (2n) with flowers Germination LEAVES Ovule Seed (2n) Endosperm (3n) Double fertilization Formation of pollen tube (n) Long tapering blades with parallel venation Broad to narrow leaves with netted venation STEMS Seed coat Egg Vascular bundles are scattered Vascular bundles arranged in a circle SEEDS Endosperm (3n) Embryo (2n) Contain cotyledon Flower Contain cotyledons PLANT ARCHITECTURE STEM STRUCTURE • Plant needs and solutions: - Leaves - Collection and conversion of solar energy - Stems - Positioning and support of leaves - Roots - Anchorage and absorption - Vascular system - Transport Axillary bud • • • • Cellulose-based cell walls for support and growth toward sunlight Epidermis Dicots with cortex and pith separated by ring of vascular bundles Monocots with ground tissue with scattered vascular bundles Shoot tip (terminal bud) Vessels Meristematic cell in xylem (brick-shaped cells) Epidermis Vascular bundle Young leaf Cortex Pith Flower Node Internode Epidermis Node Transverse section of a stem, with enlargement of a vascular bundle shown to the right Leaf Ring of vascular bundles divides ground tissue into cortex and pith Vascular tissues Sieve-tube members and companion cells in phloem Seeds (inside fruit) Air space Vessel in xylem Epidermis Thick-walled sclerenchyma cells forming a sheath around the mature vascular bundle Ground tissue Ground tissues Vascular bundle Withered cotyledon Fibers in phloem Shoot system Root system Root hairs Primary root Root tip Root cap Lateral root Groundvascular bundles distributed through ground tissue Transverse section of a stem, with enlargement of a vascular bundle shown to the right ROOT STRUCTURE LEAF STRUCTURE • • • • • • Sieve-tube member Companion cell in phloem in phloem Epidermis Cuticle with wax to resist desiccation (produced by epidermis) Guard cells with stomata to regulate gas exchange Mesophyll - Photosynthetic layer Dicots with palisade and spongy layers; monocots with one layer Vein - Vascular bundle for transport of materials Epidermis Endodermis Root section Palisade mesophyll Cortex Casparian strip Vein vascular bundle Endodermis Upper epidermis Casparian strip Cuticle • • • • • Bundle sheath Xylem Stoma Lower epidermis Stoma Guard cells Spongy mesophyll Movement of water through the endodermis to the center of the root Epidermis - Has root hairs for increased absorption area for water/minerals Cortex Endodermis - With casparian wax strips Stele - Central cylinder with vascular tissues inside Apoplastic pathway vs symplastic pathway: Water enters through root epidermis and passes in the spaces "between" cortex cells apoplastically unti reaching the endodermis Casparian strips prevent water from passing between endodermal cells Thus, water is forced through the cell membranes symplastically where it is filtered before reaching the vascular tissues within the stele In this way, potentially harmful substances might be removed by the selectively-permeable membranes of the endodermal cells PLANT DEVELOPMENT VASCULAR TISSUES • Xylem, used for water/mineral transport - Tracheids - Thin, hollow, dead cells with perforated, tapered ends - Vessel members (element) - Thick, hollow, dead cells with large holes on end • Phloem used for sugar/food transport - Sieve tube members (element), hollow, living cells with perforated ends - Companion cells, living cells that help keep sieve tube member cells alive Pits in wall Sieve plate One vessel member no cytoplasm (cells are dead at maturity) MERISTEMATIC TISSUES • Growth after germination • Upward growth - Epicotyl or Coleoptile - Phototropism - Plant growth and movement in response to light • Downward growth - Radicle or hypocotyl - Gravitropism - Plant growth response to gravity via statolith sensors • Meristematic tissues form all tissues of adult plant (similar to germ tissues of animals) • Apical meristems - Responsible for increase in plant height • Lateral meristem - Responsible for increase in plant diameter (girth) • Three primary meristems: - Protoderm - Epidermis - Ground meristem Cortex and ground tissues - Procambium - Vascular bundles with xylem and phloem sievetube member (alive) companion cell (alive) Portion of one vessel Portions of tracheids Portion of one sieve tube IMPORTANT SYMBIOSES WITH PLANTS • Root nodules & bacteria - Bacteria fix nitrogen and are housed in root nodules to supply "fertilizer," thus allowing the plant to thrive, even in soils that are nutrient poor • Mycorrhizae - Most plants today have an association between their roots and fungi in the soil This association, or mycorrhizae, is critical in aiding water/mineral uptake by the plant VEGETATIVE (asexual) REPRODUCTION Plants typically produce new parts/structures without sexual reproduction, thus allowing the quick spread of the plant into the immediate habitat Fleshy leaves Stem Stem Corm Bulb Apical Meristem Protoderm Ground meristem Procambium Three Primary Meristems: Vascular bundle Vascular cambium Stem of primary plant body Cork cambium Lateral Meristems (their location in stems showing secondary growth) SEEDLING DEVELOPMENT Foliage leaves New plant Cotyledon Stolon (runner) Epicotyl Rhizome Cotyledon Root Cotyledon Hypocotyl Hypocotyl Asexual Reproductive Modes of Flowering Plants Mechanism Representative Characteristics Radicle Vegetative reproduction on modified stems Runner (stolon) Strawberry Rhizome Corm Bermuda grass Gladiolus Tuber Potato Bulb Onion lily Parthenogenesis Orange tree, rose Vegetative propagation Jade plant, African violet Tissue culture propagation Orchids, lily, tulip, wheat, rice, corn New plants arise at nodes on an above ground horizontal stem New plants arise at nodes of underground horizontal stem New plant arises from axillary bud on short, thick, vertical underground stem Seed coat Bean Foliage leaves Epicotyl Hypocotyl Cotyledon New shoots arise from axillary buds on tubers (enlarged tips of slender underground rhizomes) Hypocotyl Radicle New bulb arises from axillary bud on short underground stem Embryo develops without nuclear or cellular fusion (e.g., from unfertilized haploid egg; or develops adventitiously, from tissue surrounding embryo sac) New plant develops from tissue or organ (e.g., a leaf) that drops or is separated from plant New plant induced to arise from cell of a parent plant that is not irreversibly differentiated Pea Coleoptile Radicle Corn Foliage leaves Plant development continued: • Vascular cambium - Produces xylem inward and phloem outward • Cork cambium - Cork • Wood is produced from xylem: - Annual rings (see fig.) - Heartwood vs sapwood (see fig.) - Heartwood - Clogged xylem, little water transport - Sapwood - Newer xylem, free flowing water transport • Bark is produced from phloem, cork cambium, cork - Lenticels are cracks in the bark to facilitate gas exchange - "Girdling plants" or cutting a horizontal band around the circumference of the plant, can be deadly because the vascular cambium, in which nutrients and water travel vertically, can be damaged Lawn equipment (especially weed whackers) is a potential source of this kind of plant damage • Exchange and Transport - Plants obtain gases, nutrients, minerals and water via internal fluids - Gas exchange- stomata, roots, lenticels - Internal transport- xylem and phloem - Fluids move in xylem via adhesion, cohesion, evaporation and osmosis • Theories of upward movement: - Capillary action - Some water moves up small vascular cells naturally - Root pressure - Solutes inside the root tissues draw some water up - Transpiration pull (cohesion-adhesion-tension)- The main motive force for transporting water up to the top of a plant (sometimes several hundred feet) - Essentially, as water evaporates from the leaf surface, the cohesive and adhesive properties of water pull water molecules from below, establishing a water tension/pressure One drawback is it requires loss of water from the plant In dry conditions or arid environments, this water loss for vertical transport can be critical to plants – thus, a replenishing water supply in the roots is vital • Fluid movement in phloem (see fig.) - Sugars produced by the leaves via photosynthesis must be distributed to the rest of the plant Gravity can assist this basically downward movement However, getting the sugars into the cells of the phloem requires energy (i.e active transport) Sometimes large quantities of sugars/starch are stored in special vegetative structures (e.g., tubers) SECONDARY GROWTH Xylem Heartwood Cork (with cambium) "Bark" Vascular cambium ANNUAL RINGS 1993 1992 Annual ring 1991 1990 250 um INTERNAL TRANSPORT IN PHLOEM Xylem Phloem Companion cell This QUICKSTUDY ® guide is an outline of the basic topics taught in Botany courses Due to its condensed format, use it as a Botany guide but not as a replacement for assigned class work Leaf (source of sucrose) All rights reserved No part of this publication may be reproduced or transmitted in any form, or by any means, electronic or mechanical, including photocopy, recording, or any information storage and retrieval system, without written permission from the publisher © 2001 BarCharts, Inc., Boca Raton, FL 1007 CREDITS Author: Randy Brooks, PhD Layout: Dale Nibbe Sapwood Phloem PRICE U.S $5.95 CAN $8.95 Bulk flow of solution Plasmodesmata ISBN-13: 978-142320405-3 ISBN-10: 142320405-0 Fruit (sink for sucrose) free downloads & hundreds of titles at quickstudy.com Customer Hotline # 1.800.230.9522 We welcome your feedback so we can maintain and exceed your expectations Sieve Companion cell Water Sucrose osmosis of water active transport of sucrose