The Plant Kingdom: Flowering Plants

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The Plant Kingdom Flowering Plants

• Chapter 25

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LEARNING OBJECTIVE 1

• Summarize the features that distinguish flowering
  plants from gymnosperms

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KEY TERMS

• ANGIOSPERM
• Traditional name for flowering plants
• A large, diverse phylum of plants that form
  flowers for sexual reproduction and produce seeds
  enclosed in fruits

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Flowering Plants

• Like gymnosperms
• Flowering plants have vascular tissues and
  produce seeds
• Unlike gymnosperms
• Ovules of flowering plants are enclosed within an
  ovary

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KEY TERMS

• OVULE
• Structure in the ovary that contains a female
  gametophyte and develops into a seed after
  fertilization
• OVARY
• Base of a carpel or fused carpels that contains
  ovules and develops into a fruit after
  fertilization

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Orange Fruit Development
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LEARNING OBJECTIVE 2

• Describe the ecological and economic significance
  of the flowering plants

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Ecology and Economy

• Our survival as a species depends on flowering
  plants
• Major food crops
• Products
• Cork, rubber, tobacco, coffee, chocolate,
  aromatic oils for perfumes
• Valuable lumber
• Fibers and medicines

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Economic Botany

• Subdiscipline of botany that deals with plants of
  economic importance
• Most of these are flowering plants

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LEARNING OBJECTIVE 3

• Distinguish between monocots and eudicots, the
  two largest classes of flowering plants
• Give specific examples of each class

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KEY TERMS

• COTYLEDON
• The seed leaf of a plant embryo, which may
  contain food stored for germination

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KEY TERMS

• MONOCOT
• One of two main classes of flowering plants
  monocot seeds contain a single cotyledon
• Monocots have floral parts in threes
• Monocots include grasses, orchids, irises,
  onions, lilies, palms

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KEY TERMS

• EUDICOT
• One of two main classes of flowering plants
  eudicot seeds contain two cotyledons
• Eudicots have floral parts in fours or fives
• Eudicots include oaks, roses, mustards, cacti,
  blueberries, sunflowers

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Monocots and Eudicots
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Petal
Sepal
Anther of stamen
Stigmas of pistil
(a) Monocots, such as this nodding
trillium (Trillium cernuum), have their floral
parts in threes. Note the three green sepals,
three white petals, six stamens, and three
stigmas (the compound pistil consists of three
fused carpels).
Fig. 25-2a, p. 488
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Petal
Anther of stamen
Pistils
(b) Most eudicots such as this Tacitus bellus
have floral parts in fours or fives. Note the
five petals, 10 stamens, and five separate
pistils. Five sepals are also present but barely
visible against the background.
Fig. 25-2b, p. 488
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LEARNING OBJECTIVE 4

• Briefly explain the life cycle of a flowering
  plant
• Describe double fertilization

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Life Cycle

• Flowering plants undergo an alternation of
  generations
• Sporophyte generation is larger and nutritionally
  independent
• Gametophyte generation is reduced to only a few
  microscopic cells

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KEY TERMS

• DOUBLE FERTILIZATION
• A process in the flowering plant life cycle in
  which there are two fertilizations
• One results in formation of a zygote
• Second results in formation of endosperm

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KEY TERMS

• ENDOSPERM
• The 3n nutritive tissue formed at some point in
  the development of all angiosperm seeds

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Life Cycle Flowering Plants
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Developing pollen tube of mature male gametophyte
Pollination
Each microspore develops into a pollen grain
Embryo sac (mature female gametophyte)
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5
Pollen grain (immature male gametophyte)
Microspore
Pollen tube
Tetrad of microspores
3
Polar nuclei
Megaspore
Egg nucleus
Two sperm cells
HAPLOID (n) GAMETOPHYTE GENERATION
Meiosis
Double fertilization
Ovary
DIPLOID (2n) SPOROPHYTE GENERATION
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Megaspore mother cell
Endosperm (3n)
2
4
Zygote (2n)
Megasporangium (ovule)
Fruit
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Embryo
Seed
Microspore mother cells within microsporangia
Seed coat
Seedling
1
Anther
Flower of mature sporophyte
Fig. 25-3, p. 490
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Pollen Grains
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LEARNING OBJECTIVE 5

• Discuss some of the evolutionary adaptations of
  flowering plants

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Adaptations of Flowering Plants 1

• Reproduce sexually by forming flowers
• Form seeds within fruits after double
  fertilization

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Adaptations of Flowering Plants 2

• Have efficient water-conducting vessel elements
  in xylem and carbohydrate-conducting sieve-tube
  elements in phloem
• Have pollen grains transported by wind, water,
  insects, other animals

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KEY TERMS

• APOMIXIS
• A type of reproduction in which fruits and seeds
  are formed asexually

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Adaptability of Flowering Plants
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LEARNING OBJECTIVE 6

• Trace the evolution of flowering plants from
  gymnosperms

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Evolution of Flowering Plants

• Probably descended from ancient gymnosperms with
  specialized features
• leaves with broad, expanded blades and closed
  carpels
• Probably arose only once

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Drimys piperita Carpel
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Carpel
Fused margin
Ovules
Stigma
Ovary
Style
Stigma
(a) The carpel resembles a folded leaf in which
the ovules borne on its upper surface are
enclosed.
(b) A cross section of the carpel, cut along the
dashed line in (a).
Fig. 25-6, p. 493
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Fossil Angiosperms
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Pistils
Scars on reproductive axis
Carpel
Ovule
(a) The oldest known fossil angiosperm. This
fossil of the extinct plant Archaefructus shows a
carpel-bearing stem. It was discovered in
northeastern China and is about 125 million years
old.
(b) The fossilized flower of the extinct plant
Archaeanthus linnenbergeri, which lived about 100
mya. The scars on the reproductive axis
(receptacle) may show where stamens, petals, and
sepals were originally attached but abscised
(fell off). Many spirally arranged pistils were
still attached at the time this flower
was fossilized.
Fig. 25-7, p. 494
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Evolution of Flowering Plants
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Basal Angiosperms
Core Angiosperms
Amborella
Monocots
Water lilies
Star anise
Eudicots
Magnoliids
Evolution of vessel elements
Evolution of flowering plants
(a) One hypothesis of relationships among the
flowering plants, based on fossil and molecular
evidence. Amborella, water lilies, and star anise
are living plants whose ancestors apparently
branched off the angiosperm family tree early.
These early groups were followed by the
magnoliids, the monocot branch, and the eudicots.
Fig. 25-8, p. 495
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LEARNING OBJECTIVE 7

• Distinguish between basal angiosperms and core
  angiosperms

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KEY TERMS

• BASAL ANGIOSPERM
• One of three groups of angiosperms thought to be
  ancestral to all other flowering plants
• CORE ANGIOSPERM
• Group including most angiosperm species
• Divided into three subgroups magnoliids,
  monocots, and eudicots

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KEY TERMS

• MAGNOLIID
• One of the groups of flowering plants
• Core angiosperms once classified as dicots, but
  molecular evidence indicates they are neither
  eudicots nor monocots
• Includes species in magnolia, laurel, and black
  pepper families, several related families

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LEARNING OBJECTIVE 8

• Briefly describe the distinguishing
  characteristics and give an example or two of
  each of the following flowering plant families
  magnolia, walnut, cactus, mustard, rose, pea,
  potato, pumpkin, sunflower, grass, orchid, and
  agave

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Flowering Plant Families 1

• More than 300 families
• Magnolia family
• Important ornamentals and source of timber
• Examples southern magnolia, tuliptree

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Magnolia Family
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Fig. 25-9, p. 497
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Flowering Plant Families 2

• Walnut family
• Provides nuts for food, wood for furniture
• Examples English walnut, black walnut, pecan
• Cactus family
• Important as ornamentals
• Examples prickly pear, Christmas cactus

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Walnut Family
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Female flowers
Catkin of male flowers
Fruit (a drupe)
Young tree
Compound leaf
Fruit with husk removed to show hard stone
(a) The pinnately compound leaves and green
fruits of black walnut (Juglans nigra) make the
tree easy to recognize.
Fig. 25-10a, p. 498
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Fig. 25-10b, p. 498
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Fig. 25-10c, p. 498
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Cactus Family
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Stamens
Stigma
Petals
(c) Cactus flowers contain numerous sepals,
petals, and stamens. The compound pistil consists
of two to many fused carpels. In this photo of a
prickly pear cactus (Opuntia humifusa), the
petals, stamens, and stigma are evident.
Fig. 25-11c, p. 499
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Flowering Plant Families 3

• Mustard family
• Many important food crops
• Examples cabbage, broccoli, cauliflower, turnip,
  mustard
• Rose family
• Commercially important fruits and ornamentals
• Examples apple, pear, plum, cherry, apricot,
  peach, strawberry, raspberry, rose

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Mustard Family
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Pistil
Stamen
Petal
Sepal
(a) A typical mustard flower, showing the four
petals arranged in the shape of a cross.
Fig. 25-12a, p. 501
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Mustard Family
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Mustard Family
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Mustard Family
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Rose Family
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Rose Family
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Rose Family
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Flowering Plant Families 4

• Pea family
• Important food crops
• Examples garden pea, chick pea, green bean,
  soybean, lima bean, peanut, red clover, alfalfa

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Pea Family
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Banner
Compound leaf (three leaflets)
Young fruit
Wing
Sepal
Corolla
Keel (two fused petals)
(b) Close-up of a bean flower, showing its
irregular corolla shape.
Remnants of stigma and style
Pod (fruit)
Seeds
Remnants of sepals (and sometimes petals and
stamens)
(c) The bean fruit, a legume, is opened to show
the seeds.
(a) Part of a common bean (Phaseolus
vulgaris) plant, showing flowers and developing
fruits.
Fig. 25-14a-c, p. 503
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Pea Family
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Pea Family
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Flowering Plant Families 5

• Potato family
• Important food crops and chemicals used as drugs
• Examples potato, tomato, green pepper, eggplant,
  petunia, deadly nightshade (belladonna)

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Potato Family
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Flowering Plant Families 6

• Pumpkin family
• Food crops
• Examples pumpkins, melons, squashes, cucumbers,
  cantaloupe, honeydew, muskmelon, cucumber,
  watermelon

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Pumpkin Family
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Petals fused into bell shape
Stigma
Style
Ovary
(a) Cutaway view of a female squash flower.
Note the inferior ovary located beneath the point
of attachment of the sepals and petals.
Fig. 25-16a, p. 505
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Pumpkin Family
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Anthers
(b) Cutaway view of a male squash flower.
Note the united anthers.
Fig. 25-16b, p. 505
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Pumpkin Family
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Flowering Plant Families 7

• Sunflower family
• One of the largest families of flowering plants
• Examples chrysanthemums, marigolds, sunflowers,
  daisies, and some food plants such as lettuce,
  globe artichokes

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Sunflower Family
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Ray floret
Disc floret
a) Head of a sunflower (Helianthus annuus).
Fig. 25-17a, p. 506
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Ray floret
Disc floret
Stigmas
Anther
Corolla
Ovary
(c) Female ray floret.
(d) Bisexual disc floret.
Fig. 25-17cd, p. 506
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Flowering Plant Families 8

• Grass family
• Most important family of flowering plants from
  the human standpoint
• Examples rice, wheat, corn, oats, barley, rye,
  sugarcane, bamboo

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Grass Family
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Anther
Inflorescence
Palea
Filament
Feathery stigma
Ovary
Blade
Reduced petals
Sheath
Lemma
Stolon
Rhizome
Fibrous root system
(a) The growth habit of a representative grass
plant. Grass flowers, which are wind pollinated,
are highly modified. Note, for example, the
long, feathery stigmas, adapted to efficiently
catch wind-borne pollen.
Fig. 25-18a, p. 507
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Flowering Plant Families 9

• Orchid family
• One of the largest families of flowering plants
  contains a greater variety of flowers than any
  other family
• Example the vanilla orchid
• Agave family
• Best known for ornamentals
• Examples century plant, sisal hemp, bowstring
  hemp

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Orchid Family
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Aerial roots
(a) The moth orchid (Phalaenopsis hybrid) has
photosynthetic aerial roots.
Fig. 25-19a, p. 509
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Pseudobulbs
(b) A Cymbidium hybrid has pseudobulbs that
function as storage organs.
Fig. 25-19b, p. 509
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Petal
Sepal
Lip (modified petal)
(c) Orchid flowers, such as Dendrobium,
are distinctive in that the third petal forms a
lip.
Fig. 25-19c, p. 509
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Agave Family
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Animation Monocot Life Cycle
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