The World of Plants in 41 Minutes

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The World of Plants in 41 Minutes

• Kingdom Plantae
• All are multicellular, nonmotile, autotrophic
  eukaryotes
• Their cell walls are made from cellulose
• Plants carry out photosynthesis using chlorophyll
  a and b
• Plants store their carbohydrates as starch
• Alternation of Generations - Reproduce sexually
  by alternating between gametophyte (n) and
  sporophyte (2n) generations.
• Some plants have vascular tissue (tracheophytes)
  and some have none (bryophytes)
• Mosses, ferns, gymnosperms, angiosperms

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Fig. 29-7
Origin of land plants (about 475 mya)
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Origin of vascular plants (about 420 mya)
2
3
Origin of extant seed plants (about 305 mya)
Liverworts
Nonvascular plants (bryophytes)
Land plants
Hornworts
1
ANCES- TRAL GREEN ALGA
Mosses
Lycophytes (club mosses, spike mosses, quillworts)
Seedless vascular plants
Vascular plants
2
Pterophytes (ferns, horsetails, whisk ferns)
Gymnosperms
3
Seed plants
Angiosperms
500
450
400
50
0
350
300
Millions of years ago (mya)
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Nonvascular plants (bryophytes) Seedless vascular
plants Gymnosperms Angiosperms
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Morphological and Molecular Evidence

• Many characteristics of land plants also appear
  in a variety of algal clades, mainly algae
• However, land plants share four key traits only
  with charophytes
• Rose-shaped complexes for cellulose synthesis
• Peroxisome enzymes
• Structure of flagellated sperm
• Formation of a phragmoplast

Chara species, a pond organism
5 mm
Coleochaete orbicularis, a disk-shaped
charophyte that also lives in ponds (LM)
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Bryophytes

• Bryophytes
• Bryophytes are primitive plants that lack
  vascular tissue
• They must live in moist environments because they
  have no roots or xylem and must absorb water by
  diffusion
• Bryophytes are tiny because they lack the
  lignin-fortified tissue necessary to support tall
  plants on land
• Mosses are an example

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Tracheophytes

• Tracheophytes
• Tracheophytes have transport vessels, xylem and
  phloem
• They include ancient seedless plants, like ferns,
  that reproduce by spores
• They include modern plants that reproduce by
  seeds
• Those with seeds are further subdivided into
  gymnosperms and angiosperms

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Gymnosperms

• Gymnosperms are conifers, the cone-bearing
  plants.
• Needle shape, cuticle, stomates in the stomatal
  crypts help to conserve water loss
• Cedars, sequoias, redwoods, pines, yews and
  junipers

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Angiosperms

• Flowering plants, anthophyta
• Most diverse and plentiful plants on earth
• Principle differences between Monocots and
  Eudicots

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Alternation of Generations and Multicellular,
Dependent Embryos

• Plants alternate between two multicellular
  stages, a reproductive cycle called alternation
  of generations
• The gametophyte is haploid and produces haploid
  gametes by mitosis
• Fusion of the gametes gives rise to the diploid
  sporophyte, which produces haploid spores by
  meiosis

• The diploid embryo is retained within the tissue
  of the female gametophyte
• Nutrients are transferred from parent to embryo
  through placental transfer cells
• Land plants are called embryophytes because of
  the dependency of the embryo on the parent

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Fig. 29-5a
Gamete from another plant
Gametophyte (n)
Mitosis
Mitosis
n
n
n
n
Spore
Gamete
FERTILIZATION
MEIOSIS
Zygote
2n
Mitosis
Sporophyte (2n)
Alternation of generations
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Transport in Xylem and PhloemVascular plants
have two types of vascular tissue xylem and
phloem

• Phloem consists of living cells and distributes
  sugars, amino acids, and other organic products
• Sugar-Conducting Cells of the Phloem
• Sieve-tube elements are alive at functional
  maturity, though they lack organelles
• Sieve plates are the porous end walls that allow
  fluid to flow between cells along the sieve tube
• Each sieve-tube element has a companion cell
  whose nucleus and ribosomes serve both cells

• Xylem conducts most of the water and minerals and
  includes dead cells called tracheids
• Water-conducting cells are strengthened by lignin
  and provide structural support
• Increased height was an evolutionary advantage

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Fig. 35-10d
100 µm
Vessel
Tracheids
XYLEM
Pits
Tracheids and vessels (colorized SEM)
Perforation plate
Vessel element
Vessel elements, with perforated end walls
Tracheids
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Fig. 35-10e
Sieve-tube elements longitudinal view (LM)
3 µm
Sieve plate
Sieve-tube element (left) and companion
cell cross section (TEM)
Companion cells
Sieve-tube elements
PHLOEM
Plasmodesma
Sieve plate
30 µm
10 µm
Nucleus of companion cells
Sieve-tube elements longitudinal view
Sieve plate with pores (SEM)
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Plant Growth Meristems generate cells for new
organs

• Apical meristems
• Are located at the tips of roots and in buds of
  shoots.
• Sites of cell division that allow plants to grow
  in length (primary growth)
• Lateral meristems
• results in growth which thickens the shoots and
  roots (secondary growth)

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Primary Growth lengthens roots and shoots
Cortex
Vascular cylinder
Epidermis
Key to labels
Zone of differentiation

• Zone of cell division
• Includes apical meristem
• New cells produces
• Root cap is located in root
• Zone of elongation
• Elongation of cells
• Zone of maturation
• Cell differentiation
• Cell become functionally mature

Root hair
Dermal
Ground
Vascular
Zone of elongation
Apical meristem
Zone of cell division
Root cap
100 µm
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Angiosperms
Nonvascular plants (bryophytes) Seedless vascular
plants Gymnosperms Angiosperms

• Angiosperms are seed plants with reproductive
  structures called flowers and fruits
• They are the most widespread and diverse of all
  plants

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Fig. 30-7
Stigma
Carpel
Stamen
Anther
Style
Filament
Ovary
Petal
Sepal
Ovule
Video Flower Blooming (time lapse)
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Fruits

• A fruit typically consists of a mature ovary but
  can also include other flower parts
• Fruits protect seeds and aid in their dispersal
• Mature fruits can be either fleshy or dry

Animation Fruit Development
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Fig. 30-8
Tomato
Ruby grapefruit
Nectarine
Hazelnut
Milkweed
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Fig. 30-9
Wings
Seeds within berries
Barbs
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• A pollen grain that has landed on a stigma
  germinates and the pollen tube of the male
  gametophyte grows down to the ovary
• The ovule is entered by a pore called the
  micropyle
• Double fertilization occurs when the pollen tube
  discharges two sperm into the female gametophyte
  within an ovule

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Fig. 30-10-4
Key
Haploid (n)
Diploid (2n)
Microsporangium
Anther
Microsporocytes (2n)
Mature flower onsporophyte plant(2n)
MEIOSIS
Generative cell
Microspore(n)
Ovule (2n)
Tube cell
Male gametophyte(in pollen grain)(n)
Ovary
Pollengrains
MEIOSIS
Germinatingseed
Stigma
Megasporangium(2n)
Pollentube
Embryo (2n)Endosperm (3n)Seed coat (2n)
Sperm
Seed
Megaspore(n)
Style
Antipodal cellsCentral cellSynergidsEgg (n)
Female gametophyte(embryo sac)
Pollentube
Sperm(n)
Nucleus ofdevelopingendosperm(3n)
FERTILIZATION
Zygote (2n)
Eggnucleus (n)
Discharged sperm nuclei (n)
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Fig. 30-13n
MonocotCharacteristics
EudicotCharacteristics
Embryos
One cotyledon
Two cotyledons
Leafvenation
Veins usuallyparallel
Veins usuallynetlike
Stems
Vascular tissueusually arrangedin ring
Vascular tissuescattered
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Fig. 30-13o
MonocotCharacteristics
EudicotCharacteristics
Roots
Taproot (main root)usually present
Root systemusually fibrous(no main root)
Pollen
Pollen grain withone opening
Pollen grain withthree openings
Flowers
Floral organsusually inmultiples of three
Floral organs usuallyin multiples of four or
five
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Vegetative Propegation
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Tropical Tropismstropism turning response to a
stimulus
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Table 39-1