Introduction to the Plant Kingdom: Bryophytes - PowerPoint Presentation

Slide1

Introduction to the Plant Kingdom: Bryophytes

Chapter 20Slide2

Outline

Introduction

Introduction to the Bryophytes

Phylum

Hepaticophyta

– Liverworts

Phylum

Anthocerophyta

– Hornworts

Phylum

Bryophyta

– Mosses

Human and Ecological Relevance of BryophytesSlide3

Introduction

Plants and green algae

share:

Chlorophylls a and b, carotenoids

Starch as food reserve

Cellulose in cell walls

Phragmoplast

and cell plate during cell division

Shared features suggest common

ancestor

Land plants first appeared 400

mya

Ancestor progressed from aquatic to land habitat even

earlierSlide4

Introduction

Features preventing

dessication

:

Plant surfaces developed fatty

cuticle

to retard

H

2

O loss

Gametangia

(gamete-producing structures) and

sporangia

(spore-producing structures) became multicellular and surrounded by jacket of sterile

cells

Zygotes developed into multicellular embryos within parental tissues

originally surrounding eggSlide5

Introduction to the Bryophytes

Ca.

23,000 species of bryophytes

Include mosses, liverworts, and hornworts

Occupy wide range of habitats:

Damp banks, trees, logs

Bare rocks in scorching sun

Frozen alpine slopes

In elevations from sea level up to 5,500

m or moreSlide6

Introduction to the Bryophytes

Bryophytes often have

mycorrhizal

fungi

associated with

rhizoids

Peat mosses

ecologically

important in

bogsLuminous mosses found in caves and other dark, damp places

None have true xylem or

phloem

Many have

hydroids

for

H

2

O conduction

Most

H

2

O

absorbed directly through

surface

Few have

leptoids

for

food-conduction

Need

H

2

O to

reproduce

sexuallySlide7

Introduction to the Bryophytes

Exhibit

alteration of generations

In mosses, leafy plant

= gametophyte generation

Sporophyte

generation grows from

gametophyte

3

distinct bryophyte phylaNone appear closely related to other living plantsBryophyte lines may have arisen independently from ancestral green

algaeSlide8

Phylum

Hepaticophyta

– Liverworts

Structure and form:

Most common and widespread liverworts have flattened, lobed

thalli

(singular:

thallus

)

Thalloid liverworts constitute ca. 20% of spp.Other 80% leafy

Thalli

or leafy gametophytes develops from

spores

When spores germinate they may produce

protonema

-

immature

gametophyte consisting of short filaments

T

halloid

liverworts growth

prostrate

and one-celled rhizoids on

lower

surface anchor

plantSlide9

Phylum Hepaticophyta – Liverworts

Thalloid

liverworts

Best known species in genus

Marchantia

Thallus

forks

dichotomously

as it growsEach branch apical notch and central grooveMeristematic

cells in notch continue to

divide

Bottom layer of

thallus

-

epidermis

from which

rhizoids

and

scales

ariseSlide10

Phylum

Hepaticophyta

– Liverworts

Marchantia

Upper surface

divided

into diamond-shaped segments

marking limits

of chambers

belowEach segment has small bordered pore opening into chamberShort, erect rows of cells with chloroplasts sit on floor of chambersSlide11

Phylum

Hepaticophyta

– Liverworts

Thalloid

liverworts

Marchantia

-

asexual

reproduction:Gemmae (singular: gemma) - tiny, lens-shaped pieces of tissue become detached from thallus

Produced in

gemmae

cups

scattered over upper surface of

thallusSlide12

Phylum

Hepaticophyta

– Liverworts

Thalloid

liverworts

Marchantia

-

sexual

reproduction:Gametangia formed on gametophoresMale gametophore = antheridiophore

Antheridia

containing

flagellated sperm

found on upper

surfaceSlide13

Phylum

Hepaticophyta

– Liverworts

Marchantia

-

sexual reproduction cont’d.:

Female

gametophore =

archegoniophoreArchegonia with eggs in rows and hang down beneath spokes of archegoniophoreSlide14

Phylum

Hepaticophyta

– Liverworts

Marchantia

-

sexual reproduction cont’d.:

Embryo dependent on gametophyte for

sustenance

Foot of sporophyte anchors to archegoniophoreSeta - short

stalk

Capsule

-

meiosis

produces

1

n

spores

inside

Also contains 2

n

elaters

with spiral

thickenings

Immature

sporophyte protected by

calyptra

=

caplike

tissue that grows out from

gametophyteSlide15

Phylum

Hepaticophyta

– Liverworts

Marchantia

-

sexual reproduction cont’d.:Slide16

Phylum

Hepaticophyta

– Liverworts

Leafy liverworts

2

rows of partially overlapping leaves

No midrib

Often have folds or lobes

Cells contain oil

bodies

3rd

row of

underleaves

often

present

Archegonia and antheridia produced in cuplike structures composed of modified leaves, in axils of leaves or on separate

branches

Sporophyte pushes out from among

leavesSlide17

Phylum

Anthocerophyta

– Hornworts

Structure and form:

Mature sporophytes look like miniature greenish-blackish

rods

Gametophytes

thalloid

Cells with only

1 large chloroplast

Thalli

have pores and cavities filled with mucilage

often containing N

2

-fixing bacteria

Ca. 100 spp.

worldwide

Asexual reproduction by fragmentation of

thallusSlide18

Phylum

Anthocerophyta

– Hornworts

Sexual reproduction:

Archegonia and antheridia produced in rows just beneath upper surfaces of

gametophytes

Sporophyte:

N

umerous

stomataMeristem above

foot

continually increases length of sporophyte from

base

Meiosis

produces 1

n

spores

2

n

elaters

also producedSlide19

Phylum

Bryophyta

– Mosses

Structure, form and classes:

Ca.

15,000

spp.

of

mosses

Divided into 3 classes:Peat mossesTrue mossesRock mosses

A true mossSlide20

Phylum

Bryophyta

– Mosses

Structure, form and

classes cont’d.:

Leaves of moss gametophytes have blades nearly always one-cell thick, except at midrib, and never lobed or

divided

Cells usually contain numerous

chloroplasts

Peat moss leaves have large transparent cells without chloroplasts that absorb H2O; and small, green, photosynthetic cells sandwiched

between

Axis stemlike

, without xylem or

phloem

Often with

hydroids

Cells of peat moss leavesSlide21

Phylum

Bryophyta

– Mosses

Sexual reproduction:

Gametangia

at apices of leafy

shoots

Archegonium

cylindrical with egg in swollen base, and neck above containing narrow

canal

Multicellular filaments =

paraphyses

scattered among

archegoniaSlide22

Phylum

Bryophyta

– Mosses

Sexual

reproduction cont’d.:

Antheridia on short stalks, surrounded by walls

1

cell

thick

Sperm cells, each with pair of flagella, formed insideSperm forced out top of antheridium

Paraphyses

scattered among

antheridiaSlide23

Phylum

Bryophyta

– Mosses

Sexual

reproduction cont’d.:

Archegonia release substances

attracting sperm

Sperm swim down neck of

archegonium

Zygote grows into spindle-shaped embryoTop of archegonium

splits off and forms cap on top of sporophyte =

calyptra

Mature sporophyte consists of

capsule

,

seta

and

footSlide24

Phylum

Bryophyta

– Mosses

Sexual

reproduction cont’d.:

Meiosis

produces spores inside

capsule

Peristome

, composed of 1 or 2 rows of teeth, under operculum at tip of capsule

Peristome

opens or closes in response to

humidity

Spores develop into filamentous

protonema

that produces buds

developing

into leafy

gametophytesSlide25

Phylum

Bryophyta

– Mosses

Sexual

reproduction cont’d.:Slide26

Human and Ecological Relevance of Bryophytes

Pioneer species

on bare rock after volcanic eruptions or other geological upheavals =

succession

Accumulate mineral and organic matter

utilized

by other

organisms

Retain moisture, and reduce flooding and

erosionIndicators of surface

H

2

OSlide27

Human and Ecological Relevance of Bryophytes

Peat

mosses most important bryophyte to

humans

Soil conditioner due to high absorptive

capacity

Poultice material due to antiseptic properties and

absorbency

FuelSlide28

Review

Introduction

Introduction to the Bryophytes

Phylum

Hepaticophyta

– Liverworts

Phylum

Anthocerophyta

– Hornworts

Phylum Bryophyta – MossesHuman and Ecological Relevance of Bryophytes