Chapter 27: pp. 493 - 509 Copyright © The McGraw-Hill Companies, Inc.

Transcript Chapter 27: pp. 493 - 509 Copyright © The McGraw-Hill Companies, Inc.

Chapter 27: pp. 493 - 509

Flowering Plants: Reproduction

BIOLOGY 10th Edition

Outline

      Reproductive Strategies  Alternation of generations  Flowers  Pollination  Fertilization Seed Development Fruit Types and Dispersal Seed Germination Asexual Reproduction Tissue Culture

Sexual Reproductive Strategies

 Plants have a two-stage, alternating life cycle  Sporophyte produces haploid spores by meiosis  Spores divide mitotically to become haploid gametophytes  Gametophytes produce gametes  Gametes fuse to produce a diploid zygote  Zygote divides mitotically to become the diploid sporophyte

8 anther seed 7 1 sporophyte 6 zygote FERTILIZATION egg sperm diploid (2n) 2 ovule ovary MEIOSIS haploid (n) 5 Male gametophyte (pollen grain) Female gametophyte (embryo sac) 3 microspore megaspore 4 4

Sexual Reproductive Strategies



A flower produces two types of spores

 Microspore - Male gametophyte  Undergoes mitosis  Becomes pollen grain  Megaspore - Female gametophyte  Undergoes mitosis  Becomes the female gametophyte, an embryo sac within an ovule within an ovary  Ovule becomes a seed  Ovary becomes a fruit

Flowers

 Flowering occurs 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

Flowers

 A typical flower has four whorls of modified leaves attached to a receptacle at the end of a flower stalk called a peduncle  Sepals protect the bud  Petals attract pollinators  Stamens are male portion of flower  Anther - Saclike container  Filament - Slender stalk  Carpel is the female portion of flower  Stigma - Enlarged sticky knob  Style - Slender stalk  Ovary - Enlarged base enclosing ovules

Anatomy of a Flower

stamen anther filament petal carpel stigma style ovary ovule sepal receptacle peduncle 8

Monocot vs. Eudicot Flowers

stamen s1 p2 carpel s2 p1 petal p3 sepal s3 a. Daylil y , Hemerocallis sp.

p3 p2 carpel stamen p4 petal p1 p5 b. Festive azalea, Rhododendron sp.

a: © Farley Bridges; b: © Pat Pendarvis

Flowers

   Complete vs. incomplete flowers:   Complete flowers have sepals, petals, stamens, and a carpel Incomplete flowers are missing one or more of above Perfect vs. imperfect flowers:  Perfect (bisexual) flowers have both stamens and carpels  Imperfect (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 staminate and carpellate flowers on separate plants

Corn Plants are Monoecious

a. Staminate flowers b. Carpellate flowers

a: © Arthur C. Smith III/Grant Heilman Photography, Inc.; b: © Larry Lefever/Grant Heilman Photography, Inc.

Life Cycle of Flowering Plants

anther The ovule develops into a seed containing the embryonic sporophyte and endosperm.

DOUBLE FERTILIZATION 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.

polar nuclei egg sperm Seed seed coat Mature Seed mitosis embryo endosperm (3n) diploid (2n) haploid (n) Pollination pollen tube Development of the sporophyte: Pollination occurs; a pollen grain germinates and produces a pollen sperm Mature male gametophyte tube cell nucleus ovule wall Sporophyte tube cell ovule ovary generative cell Pollen grain (male gametophyte) antipodals polar nuclei egg cell synergids Embryo sac (mature female gametophyte)

(Top): Courtesy Graham Kent; (Bottom): © Ed Reschke

Development of the male gametophyte: In pollen sacs of the anther , a microspore mother cell undergoes meiosis to produce 4 microspores each anther Development of the female gametophyte: In an ovule within an ovary, a megaspore mother cell undergoes meiosis to Produce 4 megaspores.

Pollen sac ovary Ovule Microspores develop into male gametophytes (pollen grains).

One megaspore becomes the embryo sac (female gametophyte).

microspore mother cell MEIOSIS Microspores Megaspores megaspore 3 megaspores disintegrate integument megaspore mother cell ovule wall MEIOSIS micropyle 12

Development of Male Gametophyte

 Male Gametophytes  Microspores are produced in anthers  Each anther has four pollen sacs, each with many microspore mother cells  Microspore mother cells undergo meiosis to produce microspores  Microspores undergo mitosis to produce pollen grains

Development of Female Gametophyte

 The ovary contains one or more ovules    An ovule has a central mass of parenchyma cells covered by integuments One parenchyma cell enlarges to become a megaspore mother cell   The megaspore mother cell undergoes meiosis to produce four haploid megaspores, three of which are nonfunctional The functional megaspore divides mitotically until there are eight nuclei in the female gametophyte The female gametophyte (embryo sac) contains   One egg cell associated with two synergid cells One central cell with two polar nuclei  Three antipodal cells

Pollination

 Pollination 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

Pollination

118

m a.

a: © George Bernard/Animals Animals/Earth Scenes; b: © Simko/Visuals Unlimited; c: © Dwight Kuhn

Fertilization

 When a pollen grain lands on the stigma, it germinates, forming a pollen tube  The pollen tube passes between the stigma and style to reach the micropyle of the ovule  Double fertilization occurs  One sperm nucleus unites with the egg nucleus, producing a 2n zygote  The other sperm nucleus unites with the polar nuclei, forming a 3n endosperm nucleus, which develops into the endosperm  A mature seed contains the embryo, stored food, and the seed coat

Pollinators

Aa: © Steven P. Lynch; Ab: © Robert Maier/Animals/Animals/Earth Scenes

Pollinators

Ba: © Anthony Mercieca/Photo Researchers, Inc.; Bb: © Merlin D. Tuttle/Bat Conservation International;

Seed Development

 Development of a eudicot embryo  After double fertilization, the the zygote divides repeatedly to form a proembryo and a suspensor  During the globular stage, the proembryo is a ball of cells  The outermost cells will become dermal tissue

Development of a Eudicot Embryo

 The embryo is heart shaped when cotyledons appear  The embryo enlarges, elongates, and takes on a torpedo shape  In the mature embryo,  The epicotyl is the portion between cotyledons contributing to shoot development  The hypocotyl is the portion below that contributes to stem development  The radicle is the embryonic root

Development of an Eudicot Embryo

Arabidopsis thaliana A. thaliana A. thaliana Capsella Capsella zygote endosperm nucleus endosperm embryo suspensor 1 zygote Zygote stage: Double fertilization results in zygote (true green) and endosperm.

2 basal cell Proembryo stage: Embryo (green) is multicellular and the suspensor (purple) is functional.

endosperm 3 Globular stage: Embryo is globe shaped.

cotyledons appearing 4 Heart stage: Embryo is heart shaped.

hypocotyl (root axis) epicotyl (shoot apical meristem) shoot apical meristem bending cotyledons seed coat endosperm root apical meristem radicle (root apical meristem) 5 Torpedo stage: Embryo is torpedo shaped; the cotyledons are obvious.

cotyledons 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

Monocot vs. Eudicot

seed coat plumule hypocotyl radicle cotyledon

embryo pericarp endosperm coleoptile cotyledon plumule radicle coleorhiza b.

a: © Dwight Kuhn; b: Courtesy Ray F. Evert/University of Wisconsin Madison

embryo 23

Fruit Types and Seed Dispersal

 A fruit is a mature ovary  Simple Fruits  Simple fruits are derived from single ovary with one or several chambers  Compound fruits develop from several groups of ovaries   Aggregate Fruits   Ovaries are from a single flower one one receptacle Blackberry Multiple Fruits  Ovaries are from separate flowers clustered together  Pineapple

Fruit Development

 The ovary wall thickens to become the pericarp, which can have three layers  The exocarp forms the outermost skin   The mesocarp is the fleshy tissue between the exocarp and the endocarp The endocarp is the boundary around the seeds

Fruit Types

 In fleshy fruits, the pericarp is soft and fleshy at maturity  In dry fruits, the pericarp is paper, leathery, or woody when the fruit is mature  Dehiscent - the fruit splits open when ripe  Legumes  Indehiscent - the fruit does not split open when ripe  Grains

Fruits

pericarp exocarp (skin) mesocarp (flesh) endocarp (pit contains seed) Drupe

True Berry exocarp chamber of ovary has many seeds a. A drupe is a fleshy fruit with a pit containing a single seed produced from a simple ovary.

Legume b. A berry is a fleshy fruit having seeds and pulp produced from a compound ovary.

Samara seed covered by pericarp wing pericarp seed c.

A legume is a dry dehiscent fruit produced from a simple ovary .

Aggregate Fruit d.

A samara is a dry indehiscent fruit produced from a simple ovary .

Multiple Fruit 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.

a, b: © Kingsley Stern; c: © Dr. James Richardson/Visuals Unlimited; d: © James Mauseth; e: Courtesy Robert A. Schlising; f: © Ingram Publishing/Alamy

Dispersal of Fruits

 Many dry fruits are dispersed by wind  Woolly hairs, plumes, wings  Fleshy fruits - Attract animals and provide them with food  Peaches, cherries, tomatoes

Fruit Dispersal by Animals

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

Seed Germination

 Environmental requirements for seed germination  Availability of oxygen for metabolic needs  Adequate temperature for enzyme activity  Adequate moisture for hydration of cells

plumule hypocotyl radicle seed coat cotyledon cotyledons (two) pericarp endosperm cotyledon (one) coleoptile plumule radicle coleorhiza Corn kernel Seed structure seed coat first true leaves (primary leaves) cotyledons (two) epicotyl withered cotyledons hypocotyl hypocotyl primary root secondary root primary root Bean germination and growth a.

radicle first leaf coleoptile adventitious root coleorhiza Corn germination and growth b.

coleoptile primary root true leaf prop root 32

Asexual Reproduction in Plants

 Plants contain nondifferentiated meristem tissue  Allows them to reproduce asexually by vegetative propagation  Stolons  Rhizomes  Stem cuttings  Plant hormone auxin:  Can be used to cause roots to develop  Expands the list of plants that can be propagated from cuttings

Asexual Reproduction in Plants

Parent plant stolon Asexually produced offspring

Tissue Culture of Plants

 Tissue culture is the growth of a tissue in an artificial liquid or solid culture medium  Many plant cells are totipotent  Somatic embryogenesis  Hormones stimulate development of plantlets from leaf or other tissue  Meristem culture  Auxins and cytokinins allow many new shoots to develop from a single shoot tip  Virus-free clonal plants

Tissue Culture of Plants

  Anther tissue culture   Haploid cells in pollen grains are cultured to produce haploid plantlets A diploid plantlet can be produced by adding a chemical agent that encourages chromosome doubling Suspension Culture  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

Tissue Culture in Plants

a. Protoplasts, naked cells b. Cell wall regeneration c. Aggregates of cells d. Callus, undifferentiated mass e. Somatic embryo f. Plantlet

(All): Courtesy Prof. Dr. Hans-Ulrich Koop, from

Plant Cell Reports

, 17:601-604

Review

Chapter 27: pp. 493 - 509

Flowering Plants: Reproduction

BIOLOGY 10th Edition

Chapter 27: pp. 493 - 509 Copyright © The McGraw-Hill Companies, Inc.

Transcript Chapter 27: pp. 493 - 509 Copyright © The McGraw-Hill Companies, Inc.

Flowering Plants: Reproduction

Outline

Sexual Reproductive Strategies

Sexual Reproductive Strategies

A flower produces two types of spores

Flowers

Flowers

Anatomy of a Flower

Monocot vs. Eudicot Flowers

Flowers

Corn Plants are Monoecious

Life Cycle of Flowering Plants

Development of Male Gametophyte

Development of Female Gametophyte

Pollination

Pollination

Fertilization

Pollinators

Pollinators

Seed Development

Development of a Eudicot Embryo

Development of an Eudicot Embryo

Monocot vs. Eudicot

Fruit Types and Seed Dispersal

Fruit Development

Fruit Types

Fruits

Dispersal of Fruits

Fruit Dispersal by Animals

Seed Germination

Seed Germination

Asexual Reproduction in Plants

Asexual Reproduction in Plants

Tissue Culture of Plants

Tissue Culture of Plants

Tissue Culture in Plants

Review

Flowering Plants: Reproduction

Directory