Plants
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Characteristics
Plant evolution
Lower plants
Hornwort
Orchid
Characteristics of Kingdom
• Photosynthetic autotrophs
• Eukaryotic
• Chemistry same as for green algae
* Cell walls
* Pigments
• Multicellular
* Tissues & organs
* Embryos
Characteristics of Kingdom
• Life cycle – alternation of generations
Diploid sporophyte
meiosis
zygote
fertilization
gametes
Haploid gametophyte
spores
The Plant Life cycle
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Asexual reproduction common
Sexual cycle involves alternation of two
generations
* Gametophyte – gametes, dependent on water
(at first)
* Sporophyte – spores, adapted to dry condition
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Trend in evolution – reduction of the
gametophyte (increased importance of
sporophyte)
Plant spores
• Produced by meiosis
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from sporophytes
Haploid reproductive
(dispersive) cells
Grow into a
gametophyte by mitosis
Covered by
sporopollenin
Plant gametes
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Produced by
gametophytes by
mitosis
Eggs & sperm
Fertilized egg (zygote)
grows into sporophyte
Fern egg & sperm
Plant Development
• Embryos
* Young
sporophytes
develop
from zygotes
* Protected
and nurtured
by parent
Plant Body
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Root / Shoot
Meristems
* growing points
* root/shoot tips
* (woody plants) –
sideways to form wood
* indeterminate growth
Evolved from
Charophycean
Green Algae
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Mid Paleozoic
Strong similarities
Differences
A Coleochaete B Parka (Ordovician)
From Berkeley Time Machine
Chara
Coleochaete
Plant classification
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Bryophytes – no seeds, no roots, no vascular
* Mosses, liverworts, hornworts
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Seedless, vascular plants – no seeds
* Ferns, horsetails, club mosses, whisk ferns
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Gymnosperms - seeds & cones
* Conifers, cycads, ginkgo, gnetophytes
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Flowering plants – seeds, flowers & fruits
* Primitive, Monocots, Dicots
Non-vascular plants
“Bryophytes”
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Mosses, liverworts,
hornworts
Gametophyte dominant
No roots – rhizoids
Often dependent on
available moisture
Occupy ecological niches
no other plants do
Represent first plants
Moss
Liverwort
Hornwort
Phylum Bryophyta – Mosses
• Leafy gametophytes
• Sporophytes with complex teeth
• Evolutionarily distinct group from other
bryophytes
Moss Life Cycle
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Sporophyte
* Zygote
* Embryo nurtured by gametophyte
* Mature sporophyte with
sporangium
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Gametophyte
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Spore
Protonema
Leafy gametophyte
Gametes eggs & sperm
Moss Life
Cycle
Protonema
Male leafy
gametophyte
Female leafy
gametophyte
Sporophyte
Spores
Gametophyte
Moss Life
Cycle
Sperm from
antheridia
Leafy gametophytes
Egg in
archegonium
Moss Life
Cycle
Meiosis to form
spores within
sporangium
Young
sporophyte
Zygote
Spore dispersal
by wind
Embryo
Moss Life
Cycle
Sperm from
antheridia
Egg in
archegonium
Gametophyte
“First thread” stage
Sporophyte
Zygote
Spores
Embryo
Moss links
• UBC Moss Class
• Microscopy UK
Phylum Hepatophyta Liverworts
• Sporophyte simpler than mosses
• Leafy
• Thallose
Phylum Anthocerophyta Hornworts
• Sporophyte linear tube with meristem at base
• Thalloid
• Closest bryophyte to ancestor of other plants
Moss, Rhizomnium
Moss, Tortula, whole leaf
Sphagnum bog
Sphagnum = Peat Moss
Thallose liverwort Marchantia
Leafy liverwort
Lophocolea
Hornwort, Anthoceros