Flowering Plants: Reproduction

Transcription

1 Chapter 27: pp Outline BIOLOGY 10th Edition Sylvia S. Mader Flowering Plants: Reproduction Reproductive Strategies Alternation of generations Adaptation to a land environment Royalty-Free/Corbis Fertilization Seed Development Fruit Seed Germination Asexual Reproduction Tissue Culture 1 PowerPoint Lecture Slides are prepared by Dr. Isaac Barjis, Biology Instructor Copyright The McGraw Hill Companies Inc. Permission required for reproduction or display 2 Alternation of Generations in Flowering Plants Reproductive Strategies All plants have a two-stage, alternating life cycle 8 Sporophyte produces haploid spores by meiosis Spores divide mitotically to become haploid gametophytes Gametophytes produce gametes Gametes fuse to produce zygote Zygote divides mitotically to become diploid sporophyte anther 1 7 sporophyte seed 2 diploid (2n) 6 zygote FERTILIZATION ovule ovary MEIOSIS haploid (n) 3 egg sperm 5 microspore megaspore 4 Male gametophyte (pollen grain) Female gametophyte (embryo sac) 3 4

2 Reproductive Strategies Flower produces two types of spores Microspore - Male gametophyte Undergoes mitosis Becomes pollen grain Flower develops in response to environmental signals such as day length In monocots, flower parts occur in threes and multiples of three In eudicots, flower parts occur in fours or fives and multiples of four or five Megaspore - Female gametophyte Undergoes mitosis Becomes embryo sac within an ovary, within an ovule Ovule becomes seed 5 Anatomy of a Flower Monocot vs. Eudicot stamen anther filament petal 6 carpel stigma style ovary ovule stamen s1 p2 carpel s2 p1 petal p3 sepal s3 a. Daylil y, Hemerocallis sp. p3 p2 carpel stamen p4 sepal receptacle petal p1 p5 peduncle b. Festive azalea, Rhododendron sp. a: Farley Bridges; b: Pat Pendarvis 7 8

3 Leaf-like sepals protect the bud Open flower has whorl of petals Four whorls of modified leaves attached to a receptacle at the end of a flower stalk Receptacle with a single flower is a peduncle Receptacle with several flowers is a pedicle Stamens are male portion of flower Anther - Saclike container Filament - Slender stalk Carpel is female portion of flower Stigma - Enlarged sticky knob Style - Slender stalk Ovary - Enlarged base enclosing ovules 9 Corn Plants are Monoecious Complete vs. incomplete flowers: Complete flowers have sepals, petals, stamens, and a carpel Incomplete flowers missing one or more of above Bisexual vs. unisexual flowers: 10 Bisexual flowers have both stamens and carpel Unisexual flowers have one but not the other Monoecious vs. dioecious plants Monoecious plants have staminate flowers and carpellate flowers on the same plant Dioecious plants have all staminate or all carpellate flowers a. Staminate flowers b. Carpellate flowers a: Arthur C. Smith III/Grant Heilman Photography, Inc.; b: Larry Lefever/Grant Heilman Photography, Inc

4 Life Cycle of Flowering Plants From Spores to Fertilization anther Mature Seed Development of the male gametophyte: In pollen sacs of the anther, a microspore mother cell undergoes meiosis to produce 4 microspores each seed coat The ovule develops into a seed containing the embryonic sporophyte and endosperm. anther mitosis ovule ovary Pollen sac ovary Ovule embryo microspore mother cell endosperm (3n) Sporophyte Seed MEIOSIS egg sperm Undergoes meiosis to produce microspores Mitosis produces pollen grains pollen tube occurs; a pollen grain germinates and produces a pollen sperm tube cell nucleus ovule wall tube cell Microspores Development of the sporophyte: Mature male gametophyte polar nuclei MEIOSIS haploid (n) During double fertilization, one sperm from the Male gametophyte Will fertilize the egg; another Sperm will join with polar nuclei to produce the 3n endosperm. megaspore mother cell diploid (2n) DOUBLE FERTILIZATION generative cell Megaspores ovule wall Pollen grain (male gametophyte) antipodals polar nuclei egg cell Microspores develop into male gametophytes (pollen grains). One megaspore becomes the embryo sac (female gametophyte). Male Gametophytes Microspores are produced in anthers Each anther has four pollen sacs, each with many microsporocytes Development of the female gametophyte: In an ovule within an ovary, a megaspore mother cell undergoes meiosis to Produce 4 megaspores. megaspore 3 megaspores disintegrate integument micropyle synergids Embryo sac (mature female gametophyte) (Top): Courtesy Graham Kent; (Bottom): Ed Reschke is the transfer of pollen from an anther to the stigma of a carpel Self-pollination occurs if the pollen is from the same plant Cross-pollination occurs if the pollen is from a different plant a. b. 118 µm c. 8 µm a: George Bernard/Animals Animals/Earth Scenes; b: Simko/Visuals Unlimited; c: Dwight Kuhn 15 16

5 Pollinators Pollinators a. b. Aa: Steven P. Lynch; Ab: Robert Maier/Animals/Animals/Earth Scenes a. b. Ba: Anthony Mercieca/Photo Researchers, Inc.; Bb: Merlin D. Tuttle/Bat Conservation International; 17 Production of Female Gametophyte 18 Fertilization When pollen grain lands on stigma, it germinates forming a pollen tube Passes between the stigma and style to reach the micropyle of the ovule Double fertilization occurs Ovary contains one or more ovules Ovule has mass of parenchyma cells One cell enlarges to become megasporocyte Undergoes meiois and becomes four haploid megaspores Functional megaspore divides mitotically until there are eight nuclei of a female gametophyte One sperm nucleus unites with the egg nucleus, producing a zygote Other sperm nucleus unites with the polar nuclei, forming a 3n endosperm cell 19 20

6 Development of an Eudicot Embryo Seed Development Development of eudicot embryo After double fertilization, endosperm nucleus begins to divide asymmetrically Small cell is destined to become the embryo Larger cell divides repeatedly to become a suspensor Arabidopsis thaliana endosperm endosperm nucleus A. thaliana A. thaliana endosperm cotyledons appearing Capsella shoot apical meristem zygote 1 bending cotyledons hypocotyl (root axis) epicotyl (shoot apical meristem) seed coat embryo endosperm suspensor zygote Capsella root apical meristem (root apical meristem) cotyledons basal cell Zygote stage: Double fertilization results in zygote (true green) and endosperm. 2 Proembryo stage: Embryo (green) is multicellular and the suspensor (purple) is functional. 3 Globular stage: Embryo is globe shaped. 4 Heart stage: Embryo is heart shaped. 5 Torpedo stage: Embryo is torpedo shaped; the cotyledons are obvious. 6 Mature embryo stage: The epicotyl will be the shoot system; the hypocotyl will be the root system. (Proembryo): Courtesy Dr. Chun-Ming Liu; (Torpedo): Biology Media/Photo Researchers, Inc.; (Mature embryo): Jack Bostrack/Visuals Unlimited 21 Monocot vs. Eudicot 22 Development of Eudicot Embryo During globular stage, prembryo is ball of cells Outermost cells will become dermal tissue Embryo is heart shaped when cotyledons appear seed coat plumule pericarp hypocotyl endosperm coleoptile cotyledon embryo embryo plumule cotyledon Epicotyl is portion between cotyledons contributing to shoot development Hypocotyl is portion below that contributes to stem development Radicle contributes to root development coleorhiza a. b. a: Dwight Kuhn; b: Courtesy Ray F. Evert/University of Wisconsin Madison 23 24

7 a, b: Kingsley Stern; c: Dr. James Richardson/Visuals Unlimited; d: James Mauseth; e: Courtesy Robert A. Schlising; f: Ingram Publishing/Alamy Fruit Types and Seed Dispersal Simple Fruits Simple fruits are derived from single or several united carpels Legumes are fruits that split along two sides when mature Dehiscent - Split open Indehiscent - Fail to split open Simple Fruits Fleshy Drupe Berry Pome Dry Follicle Legume Capsule Achene Nut Grain Simple Fruits Fruits Dispersal Drupe True Berry exocarp chamber of ovary has many seeds Many seeds are dispersed by wind pericarp exocarp (skin) mesocarp (flesh) Woolly hairs, plumes, wings endocarp (pit contains seed) a. A drupe is a fleshy fruit with a pit containing a single seed produced from a simple ovary. b. A berry is a fleshy fruit having seeds and pulp produced from a compound ovary. Legume Samara Fleshy fruits - Attract animals and provide them with food pericarp seed seed covered by pericarp wing c. A legume is a dry dehiscent fruit produced from a simple ovary. d. A samara is a dry indehiscent fruit produced from a simple ovary. Peaches, cherries, tomatoes Aggregate Fruit Multiple Fruit Accessory fruit - Bulk of fruit is not from ovary, but from receptacle Apples fruit from many ovaries of a single flower e. An aggregate fruit contains many fleshy fruits produced from simple ovaries of the same flower. one fruit fruits from ovaries of many flowers f. A multiple fruit contains many fused fruits produced from simple ovaries of individual flowers

8 Fruit Dispersal by Animals Compound Fruits a. b. a: Marie Read/Animals Animals/Earth Scenes; b: Scott Camazine/Photo Researchers, Inc. Compound fruits develop from several individual ovaries Aggregate Fruits Ovaries are from a single flower Blackberry Multiple Fruits Ovaries are from separate flowers clustered together Seed Germination When seed germination occurs, the embryo resumes growth and metabolic activity Length of time seeds retain their viability is quite variable Some seeds do not germinate until they have been through a dormant period Temperate zones - Cold Weather Deserts - Rain Seed Germination Environmental requirements for seed germination Availability of oxygen for metabolic needs Adequate temperature for enzyme activity Adequate moisture for hydration of cells Light (in some cases) Respiration and metabolism continue throughout dormancy, but at a reduced level 31 32

9 Eudicot and Monocot Seed Structure and Germination Asexual Reproduction in Plants Plants contain nondifferentiated meristem tissue Allows them to reproduce asexually by vegetative propagation Plant hormone auxin: pericarp cotyledons plumule (two) endosperm cotyledon (one) coleoptile hypocotyl plumule seed coat cotyledon coleorhiza Corn kernel Seed structure true leaf first true leaves (primary leaves) seed coat cotyledons (two) epicotyl withered cotyledons Can be used to cause roots to develop Expands the list of plants that can be propagated from cuttings first leaf hypocotyl coleoptile coleoptile prop root hypocotyl primary root secondary root adventitious root coleorhiza primary root primary root Corn germination and growth b. Bean germination and growth a. a: Ed Reschke; b: James Mauseth 33 Asexual Reproduction in Plants 34 Tissue Culture of Plants Tissue culture is the growth of a tissue in an artificial liquid or solid culture medium Meristem culture Parent plant Plant cells are totipotent Auxins and cytokinins allow many new shoots to develop from a single shoot tip stolon Virus-free clonal plants Suspension Culture Asexually produced offspring Rapidly growing calluses are cut into small pieces and shaken into a liquid nutrient medium Single cells or small clumps break off and form a suspension G.I. Bernard/Animals Animals/Earth Scenes 35 36

10 Tissue Culture in Plants Genetic Engineering a. Protoplasts, naked cells b. Cell wall regeneration c. Aggregates of cells Traditionally, hybridization was used to produce plants with desirable traits d. Callus, undifferentiated mass Crossing different varieties of plants Transgenic plants can now be produced by placing foreign genes into a plant Agricultural plants with improved traits e. Somatic embryo Commercial products f. Plantlet (All): Courtesy Prof. Dr. Hans-Ulrich Koop, from Plant Cell Reports, 17: Pest or insecticide resistant Human hormones, antibodies 37 Review Flowering Plants: Reproduction Alternation of generations Adaptation to a land environment Fertilization Seed Development Fruit Seed Germination Asexual Reproduction Tissue Culture BIOLOGY 10th Edition Sylvia S. Mader Chapter 27: pp Reproductive Strategies 38 Royalty-Free/Corbis PowerPoint Lecture Slides are prepared by Dr. Isaac Barjis, Biology Instructor 39 Copyright The McGraw Hill Companies Inc. Permission required for reproduction or display 40