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Kingdom Plantae
„ Plant or land plants
„ Multicellular eukaryotic organisms
composed of cells having plastids
„ Primarily live on land
„ Evolved from green algal ancestors that
lived in aquatic habitats
„ Distinguished from modern algal relatives
by adaptations to terrestrial life
„
Section 4
S i Professor Donald McFarlane
Lecture 10 Plants:
Colonization of the Land
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Streptophytes
Land plants (kingdom Plantae) (embryophytes)
Vascular plants (tracheophytes)
Euphyllophytes
Ancestry
Seed plants (spermatophytes)
Angiosperms
Ginkgo
Conifers and
gnetophytes
Gymnosperms
Cycads
Lycophytes
Pteridophytes
Mosses
Hornworts
Complex charophyceans
Other green algae
Simple charophyceans
MESOZOIC
Liverworts
CENOZOIC
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Seedless
vascular plants
Bryophytes
(nonvascular plants)
Green algae
„
Probably originated from a photosynthetic
protist ancestor having a relatively
complex
p
body
y
„
Either Chara or Coleochaete are modern
protists most closely related to ancestry of
land plants
Flowers,
fruits,
endosperm
in seeds
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Permian
Ovules, pollen,
seeds
Silurian
PALEOZOIC
Devonian
Ordovician
Millions of years ago (mya)
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Carboniferous
Euphylls (megaphylls)
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417
Filament
Lignin in walls of water-conducting
cells; cutin common on epidermis;
stomata common on plant surfaces;
dominant sporophyte generation;
true roots, stems, leaves
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490
Cambrian
543
PROTEROZOIC
Sporic life cycle, embryo, sporopollenin-walled spores, tissue-producing
apical meristem, gametangia, sporangia, xyloglucans in cell wall
Plasmodesmata, plant-specific features of cell division, eggs and sperm
Chlorophyll a and b, starch produced in plastids
2500
Common protist ancestor
of cells with side branches
KEY
Critical innovations
a:© Roland Birke/Phototake; b: © The McGraw-Hill Companies, Inc./Linda Graham, photographer; c-e: © Lee W. Wilcox; f: © B. Runk/S. Schoenberger/Grant
Heilman Photography; g:© Ed Reschke/Peter Arnold; h: © Patrick Johns/CORBIS; i: © Bob Evans/Peter Arnold; j:© Wolfgang Kaehler/Corbis; k: © Fred
Bruemmer/Peter Arnold; l: © Gallo Images/Corbis
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„
Distinctive feature of land plants
Complex
charophyceans
share several
derived traits with
land plants
„
„
Represent early adaptations to land
Bodies composed of 3D tissues
Plasmodesmata
„
Sexual
„
reproduction using
egg and smaller
sperm
„
„
Increased ability to avoid water loss
Tissues arise from apical meristems at growing tips
Able to produce thick, robust bodies
Tissues and organs with specialized functions
Distinctive reproductive features
Alternation of generations
Dry air resistant reproductive cell
Specialized structures to generate, protect, and disperse
reproductive cells
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10 plant phyla
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
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“bryophytes”
Liverworts – Hepatophyta
Mosses – Bryophyta
Hornworts – Anthocerophyta
Lycophytes – Lycophyta
Pteridophytes – Pteridophyta
Cycads – Cycadophyta
Ginkgos – Ginkgophyta
Conifers – Coniferophyta
Gnetophytes – Gnetophyta
Angiosperms – Anthophyta
Include liverworts, hornworts, and mosses
Each forms a monophyletic phyla
„ Share common structural
structural, reproductive
and ecological features
„ Models of earliest terrestrial plants
„
„
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„
Sporangium
„
Sporophyte
„
Gametophyte
„
Bryophytes display features absent from
charophycean algae but present in plants
Likely early adaptations to land
Charophycean algae display a zygotic life cycle
with a one cell diploid zygote
Bryophytes and other plants exhibit a sporic life
cycle with alternation of generations
Diploid,
(mniumSEM): © Eye of Science/Photo Researchers
spore-producing sporophyte generation
gamete-producing gametophyte generation
Haploid,
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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
KEY
Single-celled
diploid (2n)
zygote
haploid
diploid
Multicellular Sperm
haploid (n)
gametophyte
Fertilization
Spores
Meiosis
Egg
Mitosis
Mitosis
KEY
Haploid
Diploid
Clarophycean “algae”
Haploid spores
Meiosis
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New:
multicellular
diploid (2n)
sporophyte
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Sperm
Fertilization
Adaptations to life on land
Multicellular haploid
(n) gametophyte
Single-celled
diploid (2n)
zygote
Egg
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Spores
Spore
dispersal tip
Meiosis
Multicellular diploid sporophyte generation
advantageous because it allows a single
plant to disperse
p
p
widely
y by
y using
g meiosis
to produce numerous, genetically variable
haploid spores
„ Each spore has the potential to grow into
a gametophyte
„
Mitosis
(a) Zygotic life cycle of charophyceans
Evolutiona
ary change
Sporophyte
KE Y
Haploid
Diploid
Gametophyte
Sperm
Fertilization
Multicellular
haploid (n)
gametophyte
Egg
© Lee W. Wilcox
Single-celled
diploid (2n)
zygote
Mitosis
Mitosis
Meiosis
New:
multicellular
diploid (2n)
sporophyte
(b) Sporic life cycle of early plants
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Gametophytes
„
„
„
Sporophytes
„
Role to produce haploid gametes
Produced by mitosis
Gametangia protects developing gametes from
d i outt and
drying
d microbial
i bi l attack
tt k
Antheridia
„
– round or elongate gametangia producing
sperm
Archegonia
„
Sperm swim to egg and fuse to form diploid
zygote
Zygotes grow into sporophytes
„
„
– flask shaped gametangia enclosing an
egg
„
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„
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Matrotrophy – zygotes remain sheltered and fed
within gametophyte tissue
Embryophytes – all land plants have
p
embryos
y
matrotrophic
When mature, spores are produced in protective
enclosures known as sporangia
Plant spore cell walls contain sporopollenin to
help prevent cellular damage
During evolution, plant sporophytes become
larger and more complex
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Distinguishing bryophyte features
„
Gametophytes dominant generation
As
opposed to dominant sporophyte
generation in other plants
„
Sporophytes are dependent on
gametophtye – small and short lived
As
opposed to independent, large and longlived in other plants
„
Nonvascular or lacking tissues for
structural support and conduction found in
other plants (vascular plants)
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„
Lycophytes and pteridophytes
Pteridophytes – about 12,000 species of
horsetails, whisk ferns and other ferns
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Vascular plants
that do not produce
seeds
„ Lycophytes- more
numerous and
larger in the past
but now about
1000 relatively
small species
„
Sporangia
Stem
Small leaves
© Lee W. Wilcox
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Roots, stems and leaves
„
Diverged prior to the origin of seeds
Seedless
„
„
vascular plants
Stems
Contain
vascular tissue and produce leaves
and sporangia
Contain phloem and xylem (contains
tracheids and lignin)
Lycophytes, pteridophytes and seedproducing plants are vascular plants or
tracheophytes
„
Possess
tracheids for water and mineral
conduction and structural support
Vascular tissues occur in the major plant
organs: stems, roots, and leaves
Roots
Specialized
for uptake of water and minerals
from the soil
„
Leaves
Photosynthetic
function
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Adaptations That Foster Stable Internal
Water Content
Life cycle
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Vascular tissue
„
„
„
„
Waxy cuticle present on
most surfaces of vascular
plant sporophytes
Cutin found in cuticle that
helps prevent pathogen
attack
Wax prevents dessication
Stomata are pores that
open and close to allow
gas exchange while
minimizing water loss
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„
Stomate
„
Cuticle
120 mm
(a) Stem showing tracheophyte adaptations
Lycophyte and pteridophyte reproduction is
limited by dry conditions, as is the case for
bryophytes
However, if fertilization occurs, lycophytes and
pteridophytes can produce many more spores
due to their larger sporophyte generation
Vascular
Stomata
(b) Close-up of stomata
a: © The McGraw-Hill Companies, Inc./Linda Graham, photographer; b: © Lee W. Wilcox
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plant sporophytes are dependent upon
maternal gametophytes for only a short time during
early embryo development
Stems of vascular plant sporophytes are able to
produce branches, forming relatively large adult
plants having many leaves
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Sporophyte
(sporophyte): © Barrett & MacKay Photography; Companies, Inc. Permission required for reproduction or display
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