Plant Diversity

1
Plant Diversity

• Chapters 29-30

2
Characteristics Shared with Protists

• red, brown, green algae
• multicellular
• eukaryotic
• photosynthetic autotrophs
• brown green algae, dinoflagellates
• cell walls made of cellulose
• green algae, euglenids, some dinoflagellates
• chloroplasts with chlorophylls a and b
• charophyceans (closest relatives)
• rose-shaped complexes for cellulose synthesis
• peroxisome enzymes
• structure of flagellated sperm
• formation of phragmoplast (cell plate) during
  cytokinesis

3
Defining the Plant Kingdom

• traditional scheme
• only members are embryophytes (plants with
  embryos)
• proposed scheme 1
• include closely related green algae in a broader
  kingdom called Streptophyta
• proposed scheme 2
• include all green algae in an even broader
  kingdom called Viridiplantae

4
Terrestrial Adaptationsof Land Plants

• apical meristems
• regions of cell division at the tips of shoots
  roots
• alternation of generations
• life cycle alternates between two multicellular
  bodies (one haploid, one diploid) see details on
  next slide
• walled spores produced in sporangia
• walls contain sporopollenin which makes the
  spores touch and resistant to harsh environments
• multicellular gametangia
• organs for producing gametes (called archegonia
  in females antheridia in males)
• multicellular, dependent embryos
• parental tissues provide the developing embryo
  with nutrients through placental transfer cells
  in the embryo

5
Alternation of Generations

• gametophyte haploid multicellular body
• results from mitotic division of haploid spores
• produces haploid gametes by mitosis
• the gametes then fuse to form a diploid zygote
• sporophyte diploid multicellular body
• results from mitotic division of diploid zygote
• produces haploid spores by meiosis
• the haploid spores divide by mitosis to form the
  gametophyte

6
Additional Derived Traitsrelated to terrestrial
life

• cuticle
• waxy, waterproofing layer that prevents excessive
  water loss protects against microbial attack
• secondary compounds
• alkaloids, terpenes, tannins
• have a bitter taste, strong odor, or toxic effect
  that helps defend against herbivores parasites
• phenolics like flavonoids
• absorb harmful UV radiation
• may act as signals in symbiotic relationships
  with soil microbes
• can deter attack by pathogenic microbes

7
Classification of Land Plants

• nonvascular plants (bryophytes)
• lack vascular tissue (cells joined into tubes
  that transport water nutrients)
• includes liverworts, hornworts, mosses
• appeared 475 mya
• vascular plants
• seedless vascular plants
• includes lycophytes (club mosses their
  relatives) pterophytes (ferns their
  relatives)
• appeared 420 mya
• seed plants
• embryos are packaged with nutrients in a
  protective coat (seed)
• includes gymnosperms angiosperms
• appeared 360 mya

8
Nonvascular Plants (Bryophytes)

• herbaceous (nonwoody) plants
• 3 phyla
• Hepatophyta (liverworts)
• Anthocerophyta (hornworts)
• Bryophyta (mosses)

9
Bryophyte Life Cycle

• gametophytes are larger longer living than the
  sporophytes
• generally form ground-hugging carpets are only
  a few cells thick
• anchored by delicate rhizoids (long, tubular
  cells or filaments of cells) rhizoids do not
  play a primary role in water mineral absorption
  like true roots
• produce gametes in gametangia
• in non-bisexual species, sperm must swim through
  a film of water to reach the eggs
• sporophytes cannot live independently they
  remain attached to their parental gametophyte
• sporophyte embryos remain in archegonia, which
  supplies nutrients to the sporophyte as it
  develops to maturity
• foot absorbs nutrients from the gametophyte
• seta (stalk) conducts these nutrients to the
  sporangium (capsule) which uses them to produce
  spores by meiosis

10
moss gametophyte
archegonium
moss sporophyte
Key Stages in Moss Life Cycle
calyptra
peristome
moss sporangium
spores
protonema (produces buds that grow into
gametophytes)
11
Moss Life Cycle