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Kingdom Plantae
Bryophyta: Nonvascular Plants
Lycophyta, Sphenophyta, Pterophyta:
Seedless Vascular Plants
Gymnosperms: Coniferophyta
Setting the Stage for Plants
• Earth’s atmosphere was originally oxygen
free
• Ultraviolet radiation bombarded the
surface
• Photosynthetic cells produced oxygen and
allowed formation of a protective ozone
layer
Invading the Land
• Cyanobacteria were probably the first to
spread into and up freshwater streams
• Later, green algae and fungi made the
journey together
• Every plant is descended from species of
green algae
The Plant Kingdom
• Nearly all are multicelled
• Vast majority are photoautotrophs
– Energy from sun
– Carbon dioxide from air
– Minerals dissolved in water
Evolutionary Tree for Plants
green zygophytes, charophytes bryophytes lycophytes
algae
related
groups
horsetails
ferns
cycads ginkgos conifers gnetophytes
flowering
plants
seed plants
euphyllophytes
embryophytes (land plants)
vascular plants
(closely related groups)
Figure 23.3
Page 387
Nonvascular Plants
• Bryophytes
• Fewer than 19,000 species
• Three groups
Liverworts
Hornworts
Mosses
Vascular Plants
• Majority of plants
• Have internal tissues that carry water
and solutes
• Two groups
– Seedless vascular plants
– Seed-bearing vascular plants
Seedless Vascular Plants
• Arose during the Devonian
• Produce spores but no seeds
• Four main groups
Whisk ferns
Lycophytes
Horsetails
Ferns
Seed-Bearing Vascular Plants
• Gymnosperms arose first
– Cycads
– Ginkgos
– Gnetophytes
– Conifers
• Angiosperms arose later
– Monocots
– Dicots
Evolutionary Trend
zygote
GREEN ALGA
BRYOPHYTE
FERN
GYMNOSPERM
ANGIOSPERM
Adaptations to Land
• Root systems
• Shoot systems
• Vascular tissues
• Waxy cuticle
Traits of
Seed-Bearing Plants
• Pollen grains
– Arise from megaspores
– Develop into male gametophytes
– Can be transported without water
• Seeds
– Embryo sporophyte inside nutritive tissues
and a protective coat
– Can withstand hostile conditions
Bryophytes
• Small, nonvascular, nonwooody
• Gametophyte dominates life cycle;
has leaflike, stemlike, and rootlike
parts
• Usually live in wet habitats
• Flagellated sperm require water to
reach eggs
Moss Life Cycle
zygote
Zygote grows,
develops into a
sporophyte while
still attached to
gametophyte.
mature
sporophyte
Diploid Stage
Fertilization
Haploid Stage
Meiosis
Spores
germinate.
spermproducing
structure
Figure 23.5
Page 388
eggproducing
structure
male
gametophyte
female
gametophyte
Phylum Bryophyta
“Mosses”
The gametophyte of
mosses consists of a
leafy shoot that is
anchored to the
substrate by branched
multicellular rhizoids.
http://www.science.siu.edu/landplants/Bryophyta/MossDesc.html
Leaf arrangement is normally spiralled.
The initial stage of gametophyte development, resulting
from germination of the spore,
is a filamentous branched structure known as the
protonema.
Moss, highly branched with sporophytes terminating lateral
branches.
Antheridia are
equally elongated
with a long narrow
stalk
General
morphology are
seen in Sphagnum
Sporophyte
Habit shot of
female shoots
with terminal
sporophytes and
male shoots with
clusters of
orange antheridia
surrounded by
leaves. Copyright
by Alan Heilman
(Univ. Tenn.).
Close-up of
gametophyte with
orange antheridia
(right) and
sporophyte (left).
Marchantia: A Liverwort
• Reproduces
asexually by
gemmae
Do not
post on
Internet
• Gametophytes are
male or female
Female gametophyte
Figure 23.7
Page 389
Seedless Vascular Plants
Lycophytes (Lycophyta)
Whisk ferns (Psilophyta)
Horsetails (Sphenophyta)
Ferns (Pterophyta)
Ferns (Pterophyta)
• 12,000 species, mostly tropical
• Most common sporophyte structure
– Perennial underground stem (rhizome)
– Roots and fronds arise from rhizome
– Young fronds are coiled “fiddleheads”
– Mature fronds divided into leaflets
– Spores form on lower surface of some
fronds
Phylum Pterophyta
“ferns”
Pattern of uncoiling “fiddle heads”.
young “Fronds”
Fern Life Cycle
Sporophyte still attached
to gametophyte
sorus
zygote
fertilization
egg
rhizome
Diploid Stage
meiosis
Haploid Stage
Spores develop
Spores
are
released
sperm
mature
gametophyte
Spore germinates
On the back (abaxial) side of the frond occur
the spore-producing structures called sori
(singular sorus).
The sori are covered by a thin structure called
an indusium.
Male (left)  Bisexual (Right)
Prothallus (gametophyte)
On the underside (ventral) of the prothallus, archegonia are
frequently clustered around the apical notch as evidenced by the
protruding archegonial necks seen in this SEM photo (by Joan
Nester-Hudson).
Biflagellated sperm
At the moment of fertilization, the nuclei of sperm and egg fuse
and a diploid zygote is formed. This begins the sporophytic
generation again. The zygote divides mitotically to form and
embryo and eventually a tiny sporophytic plant. These can often
be seen still attached to the notch area of the prothallus.
Division Lycophyta
“Club Mosses”
The sporophyte is relatively simple with dichotomously to
pseudomonopodally branched green stems and spirally arranged
microphylls (simple leaves with single veins).
Typically, the shoot system is separated into upright
aerial shoots and morphologically distinct creeping
rhizomes from which adventitious roots arise.
Sporangia are positioned on the adaxial side of specialized leaves
that in turn are arranged in zones along the stem or in a terminal
series, known as strobili
Division Sphenophyta
“Horsetails or Scouring Rushes”
The sporophyte of Equisetum is differentiated into an underground
rhizome that bears adventitious roots and an upright,
photosynthetic stem with whorls of microphylls. The stem is
jointed, i.e., the nodes are clearly defined by whorls of leaves.
Species in the subgenus Equisetum produce abundant
branches that arise in whorls at the nodes.
The eusporangia of
Equisetum are
aggregated in
terminal branched
units known as
strobili.
Strobili
Thousands of rounded spores are produced in each
sporangium
Antheridia and biflagellated spermatozoids
Division Coniferophyta
“Conifers”
Cluster of microsporangiate strobili of Pinus resinosa
Longitudinal section through a
microsporangiate cone of pine consisting of
microsporophylls spirally arranged around the
central axis bearing microsporophylls.
Male gametophyte: pollen grain
Cross section of a pine needle