How Plants Colonized Land

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Life Cycle of a Bryophyte > Moss Gametophyte is the Dominant Generation

Key

Haploid (n)

Diploid (2n)

Protonema

(n)

“Bud”

“Bud”

Male

gametophyte

(n)

Female

gametophyte (n)

Gametophore

Rhizoid

Spores

Spore

dispersal

Peristome

Sporangium

MEIOSIS

Seta

Capsule

(sporangium)

Foot

Mature

sporophytes

Capsule with

peristome (SEM)

Female

gametophytes

2 mm

Raindrop

Sperm

Antheridia

Egg

Archegonia

FERTILIZATION

(within archegonium)

Zygote

(2n)

Embryo

Archegonium

Young

sporophyte

(2n)

Slide 23

A spore germinates into a gametophyte composed of a protonema and gamete-producing gametophore.

Rhizoids anchor gametophytes to substrate.

The height of gametophytes is constrained by lack of vascular tissues.

Mature gametophytes produce flagellated sperm in antheridia and an egg in each archegonium.

Sperm swim through a film of water to reach and fertilize the egg.

Slide 24

Bryophyte Structures

Thallus

Gametophore of

female gametophyte

Marchantia polymorpha,

a “thalloid” liverwort

Marchantia sporophyte (LM)

Sporophyte

Foot

Seta

Capsule

(sporangium)

500 µm

Slide 25

The Ecological and Economic Importance of Mosses

Moses are capable of inhabiting diverse and sometimes extreme environments, but are especially common in moist forests and wetlands.

Some mosses might help retain nitrogen in the soil.

Sphagnum, or “peat moss,” forms extensive deposits of partially decayed organic material known as peat.

Sphagnum is an important global reservoir of organic carbon.

Slide 26

Bryophytes / Moss may help retain Nitrogen in the soil, an Ecological Advantage

RESULTS

With moss

Without moss

Annual nitrogen loss

(kg/ha)

0

1

2

3

4

5

6

Slide 27

Sphagnum, or peat moss: economic and archaeological significance

(a) Peat being harvested from a peat bog.

(b) “Tollund Man,” a bog mummy: The acidic, oxygen poor conditions

can preserve bodies.

Slide 28

Concept 29.3: Ferns and other seedless vascular plants were the first plants to grow tall

Bryophytes and bryophyte-like plants were the vegetation during the first 100 million years of plant evolution.

Vascular plants began to diversify during the Devonian and Carboniferous periods.