Plant Diversity What is a Plant?

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Biology 1030
Winter 2009
Plant Diversity
Chapter 29 (573-588)
Chapter 30 (591-606)
Scott circa 2009
What is a Plant?
•
Plants are characterized by multiple traits:
–
Autotrophic
–
Cell walls
–
Storage material is starch
–
Bodies made of three organ types
–
Haplodiplontic life cycle
•
–
Two multicellular stages
They have tissues which develop from apical
meristems
Scott circa 2009
1
Biology 1030
Winter 2009
Plant Phyla
• ~300,000 species
• 10 phyla exist
• Three major groups
– Bryophytes
• Bryophyta – mosses
– Seedless vascular plants
• Pterophyta – ferns
– Seed plants
• Coniferophyta – conifers
• Anthophyta – flowering plants
Scott circa 2009
Phyla You Don’t Need to Know
• You are not responsible to know these phyla
–
–
–
–
–
–
Hepatophyta
p p y
Anthocerophyta
Lycophyta
Cycadophyta
Ginkophyta
Gnetophyta
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Biology 1030
Winter 2009
Alternation of Generations
• Two multicellular stages
– Gametes (n)
– Zygote
Gametophyte
Mitosis
n
n
• Mitosis
n
Spore
– Sporophyte
• Meiosis
Mitosis
MEIOSIS
n
Gamete
FERTILIZATION
– Spores
• Mitosis
2n
– Gametophyte
– Gametes
Zygote
Mitosis
Sporophyte
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Sporophytes
• Multicellular, diploid
– Grow from zygote
– May have vascular tissue
• Function
– Sporangia (sporangium)
Spores
– Sporocytes
Spores
Sporangium
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Biology 1030
Winter 2009
Gametophytes
• Multicellular, haploid
– Grow from spores
– Never have vascular tissue
• Function
– Gametangia
• Archegonia (female)
• Antheridia (male)
Eggs
Sperm
(inside)
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Basic Plant Body
• Three organs
Apical bud
ground
• Below g
1. Roots
• Above ground
2. Stems (shoots)
3. Leaves
Shoot
system
Vegetative
shoot
Leaf
St
Stem
• Vascular tissue
• Waxy cuticle
Root
system
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Biology 1030
Winter 2009
Evolution of Land Plants
1.
2.
Green algae ancestor
Non-vascular plants
–
3
3.
• Apparent trends
–
–
–
–
Bryophytes
V
Vascular
l plants
l t
–
–
Non-seed plants
Seed plants
True organs
Dominant generation
Dependency on water
Size and complexity
Liverworts
GREEN
ALGA 1
Hornworts
Mosses
Lycophytes (club mosses,
spike mosses, quillworts)
2
Pterophytes (ferns,
horsetails, whisk ferns)
Gymnosperms
3
Angiosperms
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500
450
400
350
300
Millions of years ago (mya)
50
0
Phylum Bryophyta
• Perennial gametophyte
– Protonema(ta)
– Gametophores
– Apical meristem
• Dioecious gametophytes
– Male & female
– Gametangia on mature plants
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Biology 1030
Winter 2009
Bryophyta Body Plans
• Gametophyte
– No xylem or phloem
• Non-vascular
• Impact on size
– No true organs
• Thin ‘leaves’
• Simple ‘stems’
• Small ‘rhizoids’
– No cuticle
• Impact on environment
= A thallus
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Bryophyta Body Plans
• Sporophyte
– Dependent on the gametophyte
• Grows on
• Fed by
– Foot
– Seta
– Sporangium
• Homosporous
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Biology 1030
Winter 2009
Moss Water Loss
• All habitats
• Desiccation can occur in many
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Life on Dry Land
• Evolution of specific
structures:
– Epidermal secretions
• Cuticle
– Transport tissue
• Xylem & Phloem
Vascular
tissue
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Biology 1030
Winter 2009
Vascular Plants
• Sporophyte
dominant
– Long-lived
Long lived
– Most are perennial
• Three true organs
– Roots
– Shoots
– Leaves
• Three tissue types
• Three cell types
– Ground
– Dermal
– Vascular
– Parenchyma
– Collenchyma
– Sclerenchyma
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Phylum Pterophyta
• The ferns
– Seedless vascular plants
• Sporophyte dominant
– Perennial
– Independent gamteophyte
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Biology 1030
Winter 2009
Pterophyta Body Plans
• Short-lived gametophyte
– Thallus
• Prothallium emerges
– Small, photosynthetic
• Hormonal sex determination
– Hermaphroditic gametophyte
• Antheridiogen
g
– Male gametophyte
Scott circa 2009
Pterophyta Body Plans
• Long-lived sporophyte
– True organs
– Underground stem (= rhizome)
– Compound leaves (fronds)
• Fiddlehead
– Roots
• Shoot apical meristem
• Root apical meristems
Leaves
Rhizome
Roots
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Biology 1030
Winter 2009
Pterophyta Body Plans
• Sporangia on leaves
– Sporophylls
– Annulus
– Sporocytes
• Homospores
• Clustered in sori (sorus)
– Indusium
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The Seed Plants
• Heterosporous spore production
– Megaspores
– Microspores
• Dioecious gametophytes
– Very small
– Dependent
• Ovule develops into the seed
– Fertilization
• Pollen grain
– Carries sperm
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Biology 1030
Winter 2009
Reduced Gametophytes
• Trend
–
• Retention in megasporangium
– Protection
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Ovules & Seeds
• Gymnosperms
• Sporophyte tissue
– Integument
I t
t
– Megasporangium
• One megaspore
• Megagametophyte
– Microscopic
– Archegonia
• Fertilization
– Nutritive tissue
• Angiosperms
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Biology 1030
Winter 2009
Pollen Grains
• Sporophytes house gametophytes
– Cross fertilization
• Sperm transfer vessels
– Not dependent on water
• Male gametophytes
– Incredibly reduced
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Pollen Grains
• Dispersal
– Wind
– Wind & animals
• Pollination
– Direct
– Indirect
• Pollen tube forms
– Sperm transfer
– Fertilization IN ovule
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Biology 1030
Winter 2009
Phylum Coniferophyta
• Gymnosperms (naked seeds)
• Sporophyte dominant
• Cones
– Pollen cone – microsporangia
• Microsporophylls
– Ovulate cone – megasporangia
• Megasprorphylls
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Coniferophyta Body Plans
• Sporophytes
• Most are evergreens
– Leaves
L
are simple
i
l needles
dl
– Thick cuticle
• Very long lived
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Biology 1030
Winter 2009
Coniferophyta Body Plans
• Megagametophyte
• Microscopic – 1000s of cells
– 2-6
2 6 archegonia
h
i
• Fully dependent
• Nutrition source
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Coniferophyta Body Plans
• Microgametophyte
• Microscopic – 4 cells
– 1 tube
t b cell
ll
– 2 prothallial cells
– 1 generative cell
• Exine – coat
• Generative cell division
– Produces 2 sperm
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Biology 1030
Winter 2009
Coniferophyta Pollination
• Sperm transfer
– Advantages
• Direct pollination
– Can be a long process
• Ovule forms a naked seed
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Anthophyta
• Angiosperms (enclosed seeds)
• Sporophyte dominant
• The flowering plants
– Very successful group
• Sporangia contained in a flower
– Stamen – microsporangia
– Carpel – megasporangia
• Can be found in every environment
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Biology 1030
Winter 2009
Anthophyta Body Plans
• Sporophytes
• Two major groups
– Monocots
M
t
– (Eu)dicots
– Seed leaves
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Sporophyte Body Plans
• Embryos
– Seed leaves
• Leaf venation
• Stem vascular tissue
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Biology 1030
Winter 2009
Sporophyte Body Plans
• Roots
• Pollen grains
• Flowers
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Anthophyta Body Plans
• Megagametophyte
• Microscopic – 7 cells (8 nuclei)
–
–
–
–
Prothallial
P
th lli l (antipodal)
( ti d l)
Syngergids
Egg
Polar nuclei
• No
N archegonia
h
i
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Biology 1030
Winter 2009
Anthophyta Body Plans
• Microgametophyte
• Microscopic – only 2 cells!
– Tube
T b cell
ll
– Generative cell
• Exine – coat
• 2 sperm cells
– Double fertilization
Scott circa 2009
Anthophyta Pollination
• Sperm transfer
– Advantages
• Indirect pollination
– Double fertilization
• Seeds are enclosed
in a fruit
Pollen grain
Stigma
Pollen tube
2 sperm
Style
Ovary
Ovule
Micropyle
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Biology 1030
Winter 2009
Fruit
• Expanded flower parts
Carpels
Flower
Ovary
Stamen
Sepal
Ovule
Stigma
Ovule
Carpel
(fruitlet)
Seed
Stigma
Ovary
(in receptacle)
Remains of
stamens and styles
Sepals
Ovary
y
Stamen
Seed
Receptacle
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