Introduction to the Plant Introduction to the Plant Kingdom: BryophytesKingdom: Bryophytes

Chapter 22Chapter 22

Mosses in Olympic National Park, WA.

Sphagnum grows out onto the surface of a pond and gradually turns it into a quaking bog, which really does quake when you walk or jump on it. Eventually it becomes a bog with no free water.

Peat farmer, digging turf in Ireland.

Tollund Man, found in Denmark, was preserved by the tannic acids of a peat moss bog.

Tollund ManTollund Man• The Tollund Man lived during the late The Tollund Man lived during the late 5th century BC5th century BC and/or early and/or early

4th century BC4th century BC, about 2,400 years ago. He was buried in a , about 2,400 years ago. He was buried in a peat bogpeat bog on on the the JutlandJutland PeninsulaPeninsula in in DenmarkDenmark, a find known as a bog body. , a find known as a bog body.

• He is remarkable for the fact that his body was so well preserved that He is remarkable for the fact that his body was so well preserved that he seemed to have died only recently.he seemed to have died only recently.

• On May 6, 1950, the Højgård brothers from the small village of Tollund On May 6, 1950, the Højgård brothers from the small village of Tollund were cutting peat for their tile stove and kitchen range in the were cutting peat for their tile stove and kitchen range in the Bjældskovdal peat bog, 10 km west of Silkeborg, Denmark. Bjældskovdal peat bog, 10 km west of Silkeborg, Denmark.

• Underneath the body was a thin layer of moss. Scientists know that Underneath the body was a thin layer of moss. Scientists know that this moss was formed in Danish peat bogs in the early Iron Age about this moss was formed in Danish peat bogs in the early Iron Age about the time when Jesus was born. Therefore, the body was suspected to the time when Jesus was born. Therefore, the body was suspected to have been placed in the bog approximately 2,000 years ago during the have been placed in the bog approximately 2,000 years ago during the early Iron Age.early Iron Age.

• Subsequent C14 radiocarbon dating of Tollund Man's hair indicated Subsequent C14 radiocarbon dating of Tollund Man's hair indicated that he died in approximately 350 BC. that he died in approximately 350 BC.

• The acid in the peat, along with the lack of oxygen underneath the The acid in the peat, along with the lack of oxygen underneath the surface, had preserved the soft tissues of his body.surface, had preserved the soft tissues of his body.

• Examinations and X-rays showed that the man's head was Examinations and X-rays showed that the man's head was undamaged, and his heart, lungs and liver were well preserved.undamaged, and his heart, lungs and liver were well preserved.

LEARNING OBJECTIVE 1LEARNING OBJECTIVE 1

• Discuss some environmental Discuss some environmental challenges of living on landchallenges of living on land

• Describe how several plant adaptations Describe how several plant adaptations meet these challengesmeet these challenges

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Animation: Evolutionary Tree for Animation: Evolutionary Tree for PlantsPlants

Colonization of LandColonization of Land

• Plants required evolution of structural, Plants required evolution of structural, physiological, reproductive adaptations physiological, reproductive adaptations

• Plants produce gametes in multicellular Plants produce gametes in multicellular gametangiagametangia that contain a protective layer that contain a protective layer of sterile cells of sterile cells

KEY TERMSKEY TERMS

• CUTICLE CUTICLE • A noncellular, waxy covering over the A noncellular, waxy covering over the

epidermis of aerial plant parts that reduces epidermis of aerial plant parts that reduces water loss water loss

• STOMASTOMA • A small pore in the plant epidermis that allows A small pore in the plant epidermis that allows

gas exchange for photosynthesis gas exchange for photosynthesis

Variation in PlantsVariation in Plants

LEARNING OBJECTIVE 2LEARNING OBJECTIVE 2

• Name the algal group from which Name the algal group from which plants are hypothesized to have plants are hypothesized to have descended descended

• Describe supporting evidence Describe supporting evidence

Plant Ancestors 1Plant Ancestors 1

• Plants probably evolved from green algae Plants probably evolved from green algae

• Similar biochemical characteristics: Similar biochemical characteristics: • pigments (chlorophylls pigments (chlorophylls a a and and b, b, carotenescarotenes, ,

xanthophyllsxanthophylls) ) • cell-wall components (cellulose)cell-wall components (cellulose)• carbohydrate storage material (starch) carbohydrate storage material (starch)

Plant Ancestors 2Plant Ancestors 2

• Similar fundamental processesSimilar fundamental processes• such as cell division such as cell division

• Land plants probably descended from Land plants probably descended from charophytescharophytes (stoneworts)(stoneworts)

• Based on molecular and structural dataBased on molecular and structural data

Green algae gave rise to bryophytes.Chara is a green alga that has features similar to the alga that may have been ancestralto the bryophytes. Its growth habit is plantlike, although this may simply result from convergent evolution.

Gametangia: Plants and AlgaeGametangia: Plants and Algae

Unicellular gametangium

Developing gametes

Multicellular gametangium

Sterile cell

Fig. 22-2, p. 431

LEARNING OBJECTIVE 3LEARNING OBJECTIVE 3

• Explain what is meant by Explain what is meant by alternation of alternation of generationsgenerations

• Diagram a generalized plant life cycleDiagram a generalized plant life cycle

KEY TERMSKEY TERMS

• ALTERNATION OF GENERATIONSALTERNATION OF GENERATIONS • A type of life cycle characteristic of plants and A type of life cycle characteristic of plants and

a few algae and fungia few algae and fungi• They spend part of their life in a multicellular They spend part of their life in a multicellular nn

gametophytegametophyte generationgeneration and part in a and part in a multicellular 2multicellular 2nn sporophytesporophyte generationgeneration

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Animation: Haploid to Diploid Animation: Haploid to Diploid DominanceDominance

Plant Life CyclePlant Life Cycle

Gametophyte

Sporophyte

Zygote

HAPLOID (n)GAMETOPHYTEGENERATION

DIPLOID (2n)SPOROPHYTEGENERATION

Meiosis Fertilization

Sperm EggSpore

Embryo

Fig. 22-3, p. 431

Stepped Art

Spore

Meiosis

DIPLOID (2n) SPOROPHYTE GENERATION

Sporophyte

Zygote

Embryo

Sperm Egg

Fertilization

HAPLOID (n) GAMETOPHYTE GENERATION

Gametophyte

Fig. 22-3, p. 431

KEY TERMSKEY TERMS

• ANTHERIDIUMANTHERIDIUM • A multicellular male gametangium that A multicellular male gametangium that

produces sperm cells produces sperm cells

• ARCHEGONIUM ARCHEGONIUM • A multicellular female gametangium that A multicellular female gametangium that

produces an eggproduces an egg

Plant GametangiaPlant Gametangia

The Gametophyte GenerationThe Gametophyte Generation

• Produces haploid gametes by mitosisProduces haploid gametes by mitosis• AntheridiumAntheridium produces sperm cellsproduces sperm cells• ArchegoniumArchegonium produces an eggproduces an egg

• Fertilization: Fertilization: Gametes fuse to form a Gametes fuse to form a diploiddiploid zygotezygote

KEY TERMSKEY TERMS

• SPORE SPORE • A reproductive cell that gives rise to individual A reproductive cell that gives rise to individual

offspring in plants, fungi, and certain algae offspring in plants, fungi, and certain algae and protozoa and protozoa

The Sporophyte GenerationThe Sporophyte Generation

• First stage is First stage is zygotezygote• Develops into an embryo, protected and Develops into an embryo, protected and

nourished by gametophyte plant nourished by gametophyte plant

• Mature sporophyte plant has Mature sporophyte plant has spore spore mother cellsmother cells that undergo meiosis to that undergo meiosis to produce haploid produce haploid sporesspores

• First stage in First stage in gametophyte generationgametophyte generation

LEARNING OBJECTIVE 4LEARNING OBJECTIVE 4

• Summarize the features that Summarize the features that distinguish distinguish bryophytesbryophytes from other from other plantsplants

BryophytesBryophytes

• Small, fairly simple plantsSmall, fairly simple plants

• Nonvascular Nonvascular

• Gametophyte is dominant generationGametophyte is dominant generation• grows independently of sporophyte and is grows independently of sporophyte and is

usually perennialusually perennial

Plant EvolutionPlant Evolution

Evolution of cuticle, multicellulargametangia, multicellular embryos

Evolution of dominantsporophyte, vasculartissue

Evolutionof seeds

Greenalgal

ancestor

VASCULAR SEEDPLANTS

NONVASCULAR BRYOPHYTES

VASCULAR SEEDLESSPLANTS

An

gio

sper

ms

Gym

no

sper

ms

Fer

ns

Clu

b m

oss

es

Mo

sses

Liv

erw

ort

s

Ho

rnw

ort

s

Fig. 22-5, p. 434

LEARNING OBJECTIVE 5LEARNING OBJECTIVE 5

• Name and briefly describe the three Name and briefly describe the three phyla of bryophytes phyla of bryophytes

Three Phyla of BryophytesThree Phyla of Bryophytes

• Mosses Mosses

• LiverwortsLiverworts

• HornwortsHornworts

KEY TERMSKEY TERMS

• MOSS MOSS • A member of a phylum of spore-producing A member of a phylum of spore-producing

nonvascular plants in which the dominant nonvascular plants in which the dominant nn gametophyte alternates with a 2gametophyte alternates with a 2nn sporophyte sporophyte that remains attached to the gametophytethat remains attached to the gametophyte

MossesMosses

• Leafy moss gametophytes develop from a Leafy moss gametophytes develop from a protonema protonema

• A moss sporophyte consists of a A moss sporophyte consists of a capsulecapsule,, a a setaseta, , and a and a footfoot

KEY TERMSKEY TERMS

• PROTONEMA PROTONEMA • In mosses, a filament of In mosses, a filament of nn cells that grows cells that grows

from a spore and develops into leafy moss from a spore and develops into leafy moss gametophytes gametophytes

• CAPSULE CAPSULE • Portion of the bryophyte sporophyte in which Portion of the bryophyte sporophyte in which

spores are producedspores are produced

MossesMosses

MossesMosses

A moss that survives drought. Tortula rurali is a genus of moss that lives in regions with only occasional rainfall. During dry periods, the plant looks completely dried out and dead. However, a few minutes after rain, the plants are rehydrated and fully functional.

MossesMosses

Foot

Capsule

Seta

Fig. 22-6c, p. 435

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Animation: Moss Life Cycle

Alternation of Generation (Moss)Alternation of Generation (Moss)

• http://www.sumanasinc.com/webcontent/http://www.sumanasinc.com/webcontent/anisamples/majorsbiology/moss.htmlanisamples/majorsbiology/moss.html

Life Cycle: MossesLife Cycle: Mosses

DIPLOID (2n)SPOROPHYTEGENERATION

HAPLOID (n)GAMETOPHYTEGENERATION

Gametophyte plants

Buds onprotonema

Sporegerminates

Protonema

Sporesreleased

Meiosis

Sporemother cells thatundergo meiosis

Calyptra

Capsule

Gametophyteplant

Embryo

Zygote

Archegoniumwith egg

Antheridia at the tip ofthe gametophyte shoot

Antheridiawith spermcells

Sperm cell

Sporophyte

Fertilization

1

2

34

5

6

Fig. 22-7, p. 437

KEY TERMSKEY TERMS

• LIVERWORTLIVERWORT • A member of a phylum of spore-producing, A member of a phylum of spore-producing,

nonvascular, thalloid or leafy plants with a life nonvascular, thalloid or leafy plants with a life cycle similar to that of mosses cycle similar to that of mosses

KEY TERMSKEY TERMS

• THALLUSTHALLUS • A body that lacks roots, stems, or leavesA body that lacks roots, stems, or leaves

• GEMMA GEMMA • A small body of tissue that becomes detached A small body of tissue that becomes detached

from a parent liverwort and is capable of from a parent liverwort and is capable of developing into a new organismdeveloping into a new organism

LiverwortsLiverworts

LiverwortsLiverworts

Life Cycle: LiverwortsLife Cycle: Liverworts

DIPLOID (2n)SPOROPHYTEGENERATION

HAPLOID (n)GAMETOPHYTEGENERATION

Meiosis Fertilization

1

2

3

4

5

Antheridiophore

Germination of sporesand development ofyoung gametophyte

Sporesreleased

ArchegoniophoreMalethallus

Femalethallus

Gemmaecup

Male and femalegametophyte plants

Sporophyte

Sporemother cells thatundergo meiosis

Tissue derivedfrom archegonium

Capsule

Seta

Foot

Embryo

Zygote

Archegoniawith eggs

Antheridia withsperm cells

Spermcell

Fig. 22-9, p. 439

Liverwort Gametangia and Liverwort Gametangia and SporophyteSporophyte

Gametophyte thallus

Antheridiophore

Fig. 22-10a, p. 440

Liverwort Gametangia and Liverwort Gametangia and SporophyteSporophyte

Fig. 22-10b, p. 440

Liverwort Gametangia and Liverwort Gametangia and SporophyteSporophyte

Foot

Capsule

Seta

Fig. 22-10c, p. 440

KEY TERMSKEY TERMS

• HORNWORT HORNWORT • A member of a phylum of spore-producing, A member of a phylum of spore-producing,

nonvascular thalloid plants with a life cycle nonvascular thalloid plants with a life cycle similar to that of mosses similar to that of mosses

HornwortsHornworts

• Hornwort gametophytes are thalloid; their Hornwort gametophytes are thalloid; their sporophytes form hornlike projections out sporophytes form hornlike projections out of the gametophyte thallusof the gametophyte thallus

HornwortHornwort

Sporophyte

Gametophyte withembedded archegoniaand antheridia

Maturesporangiumsplits open

Spores

Fig. 22-11b, p. 441

LEARNING OBJECTIVE 6LEARNING OBJECTIVE 6

• Describe the ecological significance of Describe the ecological significance of the mossesthe mosses

MossesMosses

• Colonize rock previously colonized by Colonize rock previously colonized by lichenslichens

• Help form thin soil in which grasses and other Help form thin soil in which grasses and other plants can growplants can grow

• Grow in dense coloniesGrow in dense colonies• Hold soil in place, help prevent soil erosionHold soil in place, help prevent soil erosion

Mosses in ResearchMosses in Research