Today: What am I: Protistan Jeopardy! Plants, Part 1

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TodayWhat am I Protistan Jeopardy!Plants,
Part 1
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Defining the Plants

• Land plants form a monophyletic group of
  embryophytes that evolved from the green algae

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Within the Plants

• Seven major clades of Land Plants have vascular
  tissue (tracheids), the other three are
  nonvascular

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What Challenges Does Life on Land Present?
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Key Adaptations to Life on Land

• the Cuticle
• Gametangia to enclose and protect gametes
• Embryos (enclosed, protected young plants
• Pigments to protect from UV
• Spore walls from sporopollenin
• Mutualisitic associations with fungi

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Exploring Non-Vascular Plants

• Liverworts, hornworts, and mosses
• Challenges to life without a vascular system??

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Check Out the Moss Lifecycle!
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Cool Things About Mosses
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Other Seedless, Non-Vascular Plants

• Liverworts
• probably most ancient
• sporophyteas are shorter and often simpler
• lots of asexual reproduction by fragmentation
  (gemmae cups for dispersal by raindrops!)

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Other Seedless, Non-Vascular Plants

• Hornworts differ in
• the Structure of the chloroplast (plate-like)
• having Stomata
• potential for indeterminate growth of
  sporophytes (until transport becomes limiting!)

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Other Seedless, Non-Vascular Plants

• Mosses
• far more abundant today
• utilize apical cell division
• specialized cell type (hydroid) provides water
  channels (but no lignin)

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Exploring the Earliest Vascular Plants (Seedless)
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Vascular Plant Evolution

• From their bryophyte-like ancestors, inherit
• Tissue-producing meristems
• Gametangia
• Embryos and the sporo-phytes that develop from
  them
• Stomata
• Cuticles
• Sporopollenin-walled spores

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Exploring the Earliest Vascular Plants (Seedless)

• Vascular plants have xylem (water and minerals
  made primarily of tracheids) and phloem (to
  transport sugars)

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The Vascular Plants Major Changes

• Have true vascular tissue (phloem and xylem)
• Dominant sporophyte generation
• Branched sporophytes
• These early vascular plants are all seedless

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A Fern Lifecycle
What do you remember about this lifecycle??
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The GymnospermsNaked Seeds

• Whats new and exciting about the gymnosperms
  (conifers)??

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The GymnospermsNaked Seeds

• 3 Major Adaptations
• Continued reduction of gametophyte
• Evolution of the seed
• Evolution of pollen

Arabidopsis thaliana pollen grains Microscopy by
Juergen Berger, computer image manipulation by
Heiko Schoof
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1. Reduction of the Gametophyte
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2. Evolution of the Seed

• SEED sporophyte embryo packaged with a food
  supply in a protective coat.

The fossilized remains of the Jeholornis prima,
shown in an illustration, included about 50
well-preserved seeds in the bird's stomach.
(CNN.com)
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2. Evolution of the Seed
All seed plants are heterosporous! Megaspores (
female gametophytes) retained within parent
sporophyte!
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2. Evolution of the Seed

• OVULE
• (Integument Megaporangium Megaspore)
• After fertilization, the ovule develops into a
  SEED.

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3. Evolution of Pollen

• Microspores develop into pollen grains
• Pollen grains mature to become male gametophtyes
• Transfer of pollen to ovule pollination
• Doesnt require water!!

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Gymnosperms

• Ovules and seeds develop of the surface of
  specialized leaves called sporophylls

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Gymnosperm Evolution
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Gymnosperm Diversity

• Four extant phyla
• Cycads
• Ginkgos
• Gnetophyta
• Conifers

• Few species of tropical, palm-like trees
• Symbiotic with N-fixing bacteria
• Toxic to livestock!

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Gymnosperm Diversity

• Four extant phyla
• Cycads
• Ginkgos
• Gnetophyta
• Conifers

• One remaining species!
• Popular ornamental (pollution resistant)
• Produces Gingko and stinky, fleshy seeds

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Gymnosperm Diversity

• Four extant phyla
• Cycads
• Ginkgos
• Gnetophyta
• Conifers

• 3 very different genera
• Welwitschia, Gnetum, and Ephedra

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Government announces ban on ephedra Wednesday,
December 31, 2003 Posted 758 AM EST (1258 GMT)
    The debate over the safety of ephedra heated up after pitcher Steve Bechler died February 17.
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Gymnosperm Diversity

• Four extant phyla
• Cycads
• Ginkgos
• Gnetophyta
• Conifers

• Largest group (pines firs, spruces, larches,
  yews, junipers, cedars, cypresses and redwoods)
• Mostly evergreen dominant in N. hemisphere
  (where growing seasons are relatively short)

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Scale from an Ovulate Cone
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Thought Question For You
Why to Conifers do so well here? Shouldnt they
be outcompeted by the angiosperms (flowering
trees)??
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Cool Coniferous Adaptations
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Minor Modifications

• Both gymnosperms and angiosperms use tracheids in
  their xylem.
• Angiosperms also use vessel elements, and
  reinforce with fiber cells!

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Major Modification the Flower

• 4 circles of modified leaves
• Sepals (Calyx)
• Petals (Corolla)
• Stamens
• Carpels

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Hypothetical Origin of the Carpel
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Describing Flowers

• Flowers may be complete (have all four basic
  organs) or incomplete (lacking one or more)

The Magnolia, a complete flower! Photo Daniel
Mosquin
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Plants may be monoecious (one house) or dioecious
(two houses)
Are there any advantages or disadvantages to
these strategies??
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One Strategy
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Describing Flowers

• Flowers may be described as bilateral or radial.

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Describing Flowers

• Flowers may be clustered together to form an
  inflorescence

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Fruits are Mature Ovaries

• Fruits protect seeds and aid in their dispersal
• Ovary wall becomes the pericarp (thickened wall
  of the fruit)

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Fruits are Mature Ovaries
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Types of Fruit

• 1. Simple Fruit- derived from a single ovary
• 2. Aggregate Fruit- derived from a single flower
  with several carpels
• Multiple Fruit- develops from a group of flowers
  tightly clustered together (inflorescence)
• Accessory Fruits develop from additional parts

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Angiosperm Evolution and Diversity
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The Angiosperms

• Evolution of the Flower!
• Traditional taxonomy 2 Classes
• Monocots
• and
• Dicots

Jack-in-the-Pulpit, Arisaema triphyllum
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Not Monophyletic!
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Angiosperm Lifecycles

• Like the Gymnosperms
• Heterosporous
• Flower of the sporophyte produces microspores
  (will form male gametophytes) and megaspores
  (will form female gametophytes)

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Angiosperm Lifecycles

• In Angiosperms,
• Each pollen grain has two haploid cells.
• Ovules develop within the ovary, contain the
  female gametophyte or embryo sac.
• (Even further reduction of gametophyte
  generation!)

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Double
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Sporophyte Dominant An Evolutionary Trend
zygote
SPOROPHYTE (2n)
GAMETOPHYTE (n)
GREEN ALGA
BRYOPHYTE
FERN
GYMNOSPERM
ANGIOSPERM
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Cross-Pollination

• Some flowers can self-pollinate, but most use
  diverse strategies to ensure cross-pollination

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Angiosperms Shape Evolution

• By the end of the Cretaceous (65 mya) angiosperms
  are the dominant plants on Earth.
• Plants and their pollinators and dispersers are a
  good example of coevolution (mutual evolutionary
  influence)

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Other Notes about Angiosperms

• - Ecologically important
• - Major human food source
• - Source of unique secondary compounds (drugs!)
• Diversity is a non-renewable resource!

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