The Plant Kingdom

• Origins 500- 475 MYA

• 10 Phyla

• 4 Basic lifecycles

• Green algae that evolved onto land

• Evolved becoming more terrestrial, independent from water

• Then coevolved with pollinators, dispersal

Tentative Phylogeny Fig 28.8

An overview of land plant evolution

Bryophytes(nonvascular plants) Seedless vascular plants Seed plants

Vascular plants

Land plants

Origin of seed plants(about 360 mya)

Origin of vascular plants (about 420 mya)

Origin of land plants(about 475 mya)

Ancestralgreen alga

Ch

aro

ph

ycea

ns

Liv

erw

ort

s

Ho

rnw

ort

s

Mo

sse

s

Lyc

op

hyt

es(c

lub

mo

sses

, sp

ike

mo

sses

, q

uil

lwo

rts)

Pte

rop

hyt

e (f

ern

s, h

ors

etai

ls,

wh

isk

fern

)

Gym

no

sper

ms

An

gio

sper

ms

Figure 29.7

Lab

• Chara Lifecycle

• Moss Lifecycle– Liverworts

• Fern Lifecycle– Lycophytes

Charophyceans- plant’s green algae ancestor

Chara - 30 Coleochaete- 31Modern examples of charophyceans

Chara sp. (green algae)

Chara Slide #30

AntheridiaOogonia

Chara sp.

Oogonia

Antheridia

Alternation of Generations• Separate multicellular haploid and diploid

phases – (2n) Sporophyte make spores by meiosis– (n) Gametophyte makes gametes by mitosis

• Sperm and egg (moss & fern)• Pollen and Ovule (gymnosperm & angiosperm)

• The sporophyte and gametophyte are very different in morphology– Vascular tissues only appear in sporophyte phase

• Sporophyte becomes more dominant in new plant groups

• Charophyceans lack sporophyte phase

Characteristics that Plants share with the green algae group

Charophyceans

• Autotrophic Multicellular Eukaryote• Have cell walls made of cellulose

– Made by rosette cellulose-synthesizing complexes

– 20-26% of wall material, closest match in algae

• Chloroplast similarities– have chlorophyll a & b, use β-carotene as accessory

– Thylakoids stacked in grana

– Chloroplast DNA comparisons

Characteristics that Plants share with the green algae group

Charophyceans

• Peroxisome enzymes• Cell plate formation by phragmoplast• Nuclear membrane breaks down during

mitosis• Sperm ultrastructure - biflagellate• Gene sequences – rRNA, Cytoskeleton

proteins

Switch to sporophyte dominance

What’s new in Mosses?( Derived Traits)

• Spores / sporangia

• Sporophyte phase

• Upright growth on land

• Cuticle

• Multicellular gametangia

The Bryophytes

• Bryophytes are represented by three phyla:– Division Hepatophyta - liverworts– Division Anthocerophyta - hornworts– Division Bryophyta – mosses

Liverworts and hornworts are believed to be more similar to what early plants were like.

Bryophyte lifecycle: moss• Haploid dominant• No vascular tissues• Filamentous

protonema stage• Swimming sperm• Disperse by spores• Dependent

sporophyte• Dioecious

gametophytes• No true leaves• Rhizoids, not roots

Pteridophytes evolved over 400 MYASeedless, Vascular plants (having Xylem &

Phloem). Today represented by two phyla:Pterophyta: Ferns, Horsetails (Equisetum)Lycophyta: Club moss

Cooksonia, an extinct plant over 400 million years old, is the earliest known vascular plant.

Protonema

Protonema - #32

Moss Antheridia

Antheridia on stalk

Moss Antheridia # 33

Moss Archegonia

Moss Archegonia #34

Moss Archegonia #34

Moss Sporangia

Moss Sporangia- 35

Moss Sporangia- # 35

An overview of land plant evolution

Bryophytes(nonvascular plants) Seedless vascular plants Seed plants

Vascular plants

Land plants

Origin of seed plants(about 360 mya)

Origin of vascular plants (about 420 mya)

Origin of land plants(about 475 mya)

Ancestralgreen alga

Ch

aro

ph

ycea

ns

Liv

erw

ort

s

Ho

rnw

ort

s

Mo

sse

s

Lyc

op

hyt

es(c

lub

mo

sses

, sp

ike

mo

sses

, q

uil

lwo

rts)

Pte

rop

hyt

e (f

ern

s, h

ors

etai

ls,

wh

isk

fern

)

Gym

no

sper

ms

An

gio

sper

ms

Figure 29.7

WALLED SPORES PRODUCED IN SPORANGIA

MULTICELLULAR GAMETANGIA

MULTICELLULAR, DEPENDENT EMBRYOS

SporesSporangium

Longitudinal section ofSphagnum sporangium (LM)

SporophyteGametophyte

Sporophyte and sporangium of Sphagnum (a moss)

Female gametophyteArchegoniumwith egg

Antheridiumwith sperm

Malegametophyte

Archegonia and antheridia of Marchantia (a liverwort)

EmbryoMaternal tissue

2 µm

Wall ingrowthsPlacental transfer cell

10 µm

Embryo and placental transfer cell of Marchantia

Liverwort Gametophyte

Female Gametophyte

Liverwort Antheridia

• Antheridia are on the upper surface of the “umbrellas”

Liverwort Antheridia

Liverwort Archegonia

• Archegonia are on the undersides of the “umbrellas”

Liverwort Archegonia

Liverwort Archegonia - egg

Liverwort Sporangia

• On undersides- develop from archegonia

Gemmae & cups

Gemmae & cup

An overview of land plant evolution

Bryophytes(nonvascular plants) Seedless vascular plants Seed plants

Vascular plants

Land plants

Origin of seed plants(about 360 mya)

Origin of vascular plants (about 420 mya)

Origin of land plants(about 475 mya)

Ancestralgreen alga

Ch

aro

ph

ycea

ns

Liv

erw

ort

s

Ho

rnw

ort

s

Mo

sse

s

Lyc

op

hyt

es(c

lub

mo

sses

, sp

ike

mo

sses

, q

uil

lwo

rts)

Pte

rop

hyt

e (f

ern

s, h

ors

etai

ls,

wh

isk

fern

)

Gym

no

sper

ms

An

gio

sper

ms

Figure 29.7

Vascular tissue

• Allows plants to grow taller

• More support by lignified xylem tracheids

• Can pull water up from soil– Can tolerate soil that is drier on the surface

• Form parts of true leaves and roots.

• Only found in diploid tissue– Lead to sporophyte dominance?

Fern Lifecycle

• Diploid dominate• Gametophyte still independent, short lived,

– monoecious in fern (Pteridophyta)– dioecious in club “moss” (Lycophyta)

• Spores disperse plant• Sporophyte perennial

Pteridophytes evolved over 400 MYA

Seedless, Vascular plants (having Xylem & Phloem). Today represented by two divisions:

Pterophyta: Ferns, Horsetails (Equisetum)Lycophyta: Club moss

Cooksonia, an extinct plant over 400 million years old, is the earliest known vascular plant.

LYCOPHYTES (PHYLUM LYCOPHYTA)

PTEROPHYTES (PHYLUM PTEROPHYTA)

WHISK FERNS AND RELATIVES HORSETAILS FERNS

Isoetesgunnii,a quillwort

Selaginella apoda,a spike moss

Diphasiastrum tristachyum, a club moss

Strobili(clusters ofsporophylls)

Psilotumnudum,a whiskfern

Equisetumarvense,fieldhorsetail

Vegetative stem

Strobilus onfertile stem

Athyrium filix-femina, lady fern

Carboniferous forest based on fossil evidence

Fern Gametophyte # 37

Fern Gametophyte # 37

Young Sporophyte

#38

Vascular tissues in young frond

Fern Antheridia

Fern Arcghegonia

Fern Sporangia - Sori

Sporangium

Annulus

Indusium

# 40

Whisk Ferns (formerly separate phylum: Psilophyta)

Figure 29.13 Hypotheses for the evolution of leaves

Vascular tissue

Microphylls, such as those of lycophytes, may have originated as small stem outgrowths supported by single, unbranched strands of vascular tissue.

(a) Megaphylls, which have branched vascular systems, may have evolved by the fusion of branched stems.

(b)

Horsetails – Equisetum sp.(formerly separate phylum: Sphenophyta)

LYCOPHYTES (PHYLUM LYCOPHYTA)

PTEROPHYTES (PHYLUM PTEROPHYTA)

WHISK FERNS AND RELATIVES HORSETAILS FERNS

Isoetesgunnii,a quillwort

Selaginella apoda,a spike moss

Diphasiastrum tristachyum, a club moss

Strobili(clusters ofsporophylls)

Psilotumnudum,a whiskfern

Equisetumarvense,fieldhorsetail

Vegetative stem

Strobilus onfertile stem

Athyrium filix-femina, lady fern

LycophytaClub “Moss”

• Not a moss !!! ( a common name)

• Heterosporous– Meagsporania & Microsporangium– Form Strobili (cones)

Strobilus

Selaginella – strobilus #41Megasporangium

4 megaspores

Microsporangium

Many microspores

Megaspore - gametophyte

Switch to sporophyte dominance