The Plant Kingdom

1
The Plant Kingdom

• Lifes Producers

2

• General information about Kingdom Plantae. . .
• They exhibit tremendous diversity in size,
  habitat, and form
• They evolved from green algae
• Green algae and plants both contain chlorophyll
  a, b, carotenes, xanthophylls (for
  photosynthesis)
• Green algae and plants both store excess
  carbohydrates as starch
• They both contain cellulose as a major component
  of their cell walls
• They both share certain details of cell division
  (formation of cell plates)

3

• Plants are multicellular
• They are photosynthetic
• They contain a waxy cuticle to prevent
  desiccation (an adaptation representing their
  emergence from aquatic systems)
• They obtain carbon from atmospheric carbon
  dioxide
• Openings (stomata) on surface tissues permit gas
  exchange
• They have multicellular sex organs (gametangia),
  each with a sterile layer of cells surrounding
  the gametes
• Archegonium - female organ produces single egg
• Antheridium - male organ produces sperm
• The fertilized egg (zygote) develops into an
  embryo within the female gametangium

4

• The life cycle of plants. . .
• Plants have an alternation of generations -
  spending part of their lives in the haploid stage
  and part in the diploid
• The gametophyte generation - haploid portion of
  the life cycle gives rise to haploid gametes by
  mitosis
• The sporophyte generation - diploid portion of
  the life cycle gives rise to spores following
  meiosis

• The haploid gametophyte plant produces
  antheridia and archegonia
• Sperm produced in the antheridia get to the
  archegonia and swim down its neck
• One sperm fuses with the egg (fertilization),
  resulting in a 2n zygote (first stage in the
  sporophyte generation)

5

• The zygote divides mitotically and forms the
  embryo, which eventually matures into the
  sporophyte plant
• The sporophyte plant produces spore mother cells
  - which are special cells that divide by meiosis,
  forming haploid spores (first stage of the
  gametophyte generation)
• Spores grow by mitosis into mature gametophyte
  plant
• The cycle repeats

6
mitosis
7

• There are four major groups of plants. . .
• The nonvascular plants are most primitive
  (Gametophyte dominant)
• The other three groups have vascular tissues
  xylem for conducting water and minerals and
  phloem for food conduction (Sporophyte dominant)
• The vascular, seedless plants include the Ferns
  and others
• Gymnosperms reproduce by seeds, often produced in
  cones
• Angiosperms reproduce by seeds enclosed within a
  fruit

8
Kingdom Plantae (representative
Divisions)   I.                  Nonvascular
Plants (Gametophyte dominant)   Division
Bryophyta (mosses) Division Hepatophyta
(liverworts) Division Anthocerophyta
(hornworts)   II.               Vascular Plants
(Sporophyte dominant)   A.   Seedless
Plants  Division Pteridophyta (Pteridophytes) Cla
ss Polypodiopsida (ferns) Class Psilotopsida
(whisk ferns) Class Equisetopsida
(Horsetails) Division Lycophyta (Club
mosses)             B.   Seed Plants 1.    
Gymnosperms naked seeds   Division Pinophyta
(conifers) Division Cycadophyta (cycads) Division
Ginkgophyta (ginkgos) Division Gnetophyta
(gnetophytes)   2.     Angiosperms (seeds
enclosed in a fruit)   Division
Magnoliophyta             Class Magnoliopsida
(dicots)             Class Liliopsida (monocots)
9
Division Bryophyta

• Mosses and other Bryophytes

10

• General characteristics of nonvascular plants. .
  .
• Land plants that do not contain vascular tissues
  are restricted in size (they are always small and
  found in moist environments).
• Division Bryophyta are the mosses
• Most live in dense colonies or beds
• They contain rhizoids - tiny rootlike structures
  that anchor the plant to the soil
• Each plant has an upright stem that bears
  leaves
• The leafy green plant in the gametophyte

11
The moss gametophyte

• It is the dominant phase (haploid)
• Bears gametangia at the top of the plant
• Many have separate sexes others have antheridia
  and archegonia on the same plant

12

• Fertilization in Moss. . .
• Requires the presence of water
• Splashing raindrops may carry sperm to the
  archegonia
• Insects may transport a water droplet with sperm
  to archegonia
• The sperm swims down the neck of the archegonium
  and fertilizes the egg
• The zygote (2n) grows into a mature sporophyte,
  growing out of the female gametophyte
• The sporophyte (2n) is nutritionally dependent on
  the gametophyte (n)

13
The moss sporophyte

• Is composed of three main parts
• Foot - anchors the sporophyte to the gametophyte
• Seta - the stalk
• Capsule - contains spore mother cells

14

• Spore mother cells undergo meiosis, forming
  haploid spores
• Spores are released from the capsule and
  dispersed by wind or rain
• The spore germinates and grows into a filamentous
  thread (protonema)
• The protonema forms buds, each of which grows
  into a gametophyte, and the cycle continues

The gametophyte is dominant because it lives
independent of the sporophyte (this is a
primitive characteristic) Mosses are not
considered to be a direct path to higher plants
15
(No Transcript)
16
(No Transcript)
17

• Ecological and commercial importance of moss
• Moss is important in soil formation and the
  prevention of erosion
• Moss provides food for many animals
• Peat moss is important as a soil conditioner the
  large empty cells hold water
• Peat moss is burned as fuel in some countries

• The name moss is often used for plants (or
  algae) that are not true mosses (but never by a
  Biology II student?

18
Division Hepatophyta

• The Liverworts

19

• General information about liverworts. . .
• The body form is often a flattened, leaf-like,
  lobed thallus
• The lobes of the thallus resemble lobes of a
  human liver, thus their name
• Rootlike rhizoids on the underside of the thallus
  anchor the plant to the soil
• There is no vascular tissue
• These are small inconspicuous plants restricted
  primarily to damp environments
• Many are leafy like mosses and do not have a
  lobed thallus

20

• Sexual reproduction in liverworts. . .
• They produce archegonia and antheridia on the
  haploid thallus
• The life cycle is very similar to mosses, but the
  structures look different
• The sporophyte generation is attached to the
  gametophyte

• Asexual reproduction. . .
• Gemmae - balls of tissue borne in saucer-shaped
  structure (gemmae cup) directly on the thallus
• Splashing water and animals aid in dispersal of
  gemmae
• Each gemmae can grow into a thallus
• The thallus branch and grow - the older part of
  the thallus dies, leaving each extended lobe as a
  separate plant

21
(No Transcript)
22
Division Anthocerophyta The Hornworts

• The gametophyte superficially resembles the
  thalloid liverworts
• They have a single, large chloroplast in each
  cell
• Archegonia and antheridia are embedded in the
  gametophyte thallus