Flowers and Fruits

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Chapter 12

• Flowers and Fruits

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Flowers

• Sexual reproductive organs of flowering plants
• angiosperms, most diverse plant group
• produce new generations thru sexual reproduction
  embryo develops into a seed

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Parts of a Flower

• Receptacle flower parts attach here at the
  swollen area near the penduncle stalk of the
  flower
• Sepal outer whorl of floral parts all the
  sepals are called a calyx
• All the petals together make up the corolla which
  form the next whorl
• both are sterile parts of the plant and function
  to attract pollinators

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Sexual Reproduction Parts

• Male part is the stamen
• produce pollen grains that produce sperm
• made up of the anther and filament
• Female part is the pistil
• inside 1 to many ovules in each ovule is a
  single egg
• made of the stigma and the style
• Egg and sperm fuse in the ovule and develops into
  the seed
• Ovary of flower and sometimes associated parts
  becomes fruit that protects seed(s) and help in
  dispersal

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Stamens

• Produce the pollen grains
• 4 pollen-containing chambers fused into an anther
  that make pollen grains that are released thru a
  slit or thru the top
• Anther generally supported on a stalk called the
  filament
• Collection of stamens is a androecium
• variation in number and arrangement of stamens,
  attachment of anther to filament, way release
  pollen from anther

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Stamen Arrangements

• Magnolias have dozens of stamens

• Some have free stamens and others are fused at
  filaments

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Pistils

• Contain at least one ovule in their ovary and may
  be 1 or more per flower, some have one ovary with
  several carpels fused at the edge
• ovary is called the carpel
• Enlarged lower end is the ovary and the stigma is
  usually on a stalk and receives the pollen
• stalked is called the style
• raise the stigma to enhance pollination

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Female Reproductive Parts

• Carpels/pistil have no gender
• Specialized structure called the embryo sac in
  the ovule that is female
• All the carpels collectively called the gynoecium
  
• Indicators for how many carpels
• chamber for each carpel is a section in an orange
  
• stigmas or style may also reflect the number of
  carpels
• lilies have 3 seed chambers and 3 stigma but only
  one style made from 3 styles that fused
  together from 3 carpels
• 4 lobes on the stigma with 4 fused carpels

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Petals

• Often colorful, fragrant parts of flower
• Collective petals are called the corolla
  usually the most noticeable and attractive part -
  , size, color and odor distinguish between
  flowers
• Petals can be free, fused in short tube with
  large lobes, fused into long tube that
  encompasses most of the corolla honeysuckle
• aids in pollination

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Flower Symmetry

• Radially symmetrical petals develop equally

• Bilaterally symmetrical petals do not develop
  equally

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Floral Part Arrangements

• a spiral magnolia
• b whorls lily
• c petal like sepals and radial symmetry
  daffodils
• d bilateral symmetry pansy
• e petals fused into a tube cape primrose

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Sepals

• Flowers usually have a specific number of petal
  that they corresponds to the number of stamens,
  carpel and sepal
• magnolia hard to separate petals from sepals
• Leaf-like sepals protect immature flower
• may resemble petals like in the lily call them
  tepals
• 4 oclocks have a calyx (sepals) that look like a
  corolla (petals) but they have no petals
• Sepals may fuse into a tube and calyx may be
  radially or bilaterally symmetrical
• Number of sepals also can reflect the number of
  other flower parts
• same number of sepals and petals look down from
  above they alternate
• Protect inner parts of flower prevent drying
  out
• often fall off at maturity or after pollination
  and fertilization

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Embryo and Endosperm

• Plants have a sexual reproduction part to their
  life cycle
• Creates the embryo in a seed that matures into a
  plant requires the formation an egg and sperm
  for fertilization
• Most cells have diploid numbers of chromosomes
• 1 set from each parent
• Gametes are haploid these are the reproductive
  cells
• have only ½ the number of chromosomes meiosis
• fertilization produces a zygote that is diploid

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Life Cycle

• Sperm is made in the pollen grain in the anther
• Egg made in embryo sac in the ovule
• Pollen grain and egg are gametophytes of
  flowering plants
• Zygote grows in ovule becomes first cell of new
  organism

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Double Fertilization

• Fertilization requires that pollen grains from
  anther to receptive stigma of a pistil
• Embryo sac forms with a stalk and 1 or 2
  integuments that develop into seed coat
• Pollen reaches stigma and germinates to make
  pollen tube down style into the ovary
• pollen that forms the pollen tube is the tube
  cell
• 2nd cell in pollen grain is the generative cell
  as it divides and makes 2 sperm move to a small
  opening in ovule called micropyle

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Double Fertilization (cont)

• The 2 sperm move into embryo sac thru synergids
  which are cells next to the egg
• send out chemicals so that pollen can find the
  egg
• Sperm 1 fertilizes the egg to form zygote
• Sperm 2 fuses with the polar nuclei which are
  haploid near the mid region of the ovule to make
  a triploid cell 3 sets of chromosomes
• usually forms the endosperm in the seed food
  for the embryo
• Ovule matures into the seed
• Many insects visit but only pollen form same
  species sticks tightly to stigma while rest falls
  off easily
• Flowers can be used identify plants

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Reproductive Morphology

• Helps to explain diversity
• Flowering plants way out number any other group
  of plants
• Diversity in shape, size and forms
• from the reproductive success in a wide variety
  of habitats based on the development of the
  flower
• seed, fruit, pollination and the methods by which
  these things are distributed

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Variation in Basic Parts

• Some flowers lack sepals, petals, stamens or
  pistils
• Grasses have 3 stamens, 1 functional carpel (may
  have 2 non-functioning ones), no petals or sepals
• Others have either stamens or carpels but not
  both

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Flower Types

• Complete flower has all major parts sepal,
  petals, stamens and pitils
• Incomplete flower lacks one or more of the
  above parts
• Perfect flower has and androecium (collection
  of stamens) and a gymnoecium (collection of
  carpels) even if petals and sepals are missing

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Position of the Ovary

• Superior ovary base of the ovary above the
  sepals, petals and stamen St Johns wort
• Inferior ovary the sepals, petals and pistil
  rest on top of the ovary daffodil
• Incomplete ovary ovary surrounded by the
  receptacle and the petals and stamens branch from
  the receptacle above the ovary - rose

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Monocot and Dicot Flowers

• Identified by the number of their floral parts
• Monocots flower parts occur in 3 or multiples
  of 3
• 3 petals, 3 sepals, 6 stamens, 1 pistil with 3
  chambers
• mostly herbaceous plants non-woody
• Dicots flower parts in 4 or 5 or multiples of 4
  or 5
• 80 of all angiosperms herbaceous and woody

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Inflorescence

• Groups of flowers comprise an inflorescence
• lupine has an inflorescence of many on a main
  stalk peduncle
• willow has unisexual flowers packed into catkins
• Inflorescence have one peduncle with many small
  stalks called pedicles with a flower at the tip
• arrangement of pedicles on the peduncle
  characterizes the inflorescence

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Types of Infloresccence
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Types of Infloresccence

• Spike unbranched, elongated, little to no
  pedicle like spearmint
• Raceme unbranched, elongated, pedicle all about
  same length lily of the valley, snapdragons
• Panicle branched with side branches bearing
  loose clusters of flowers oat, rice, fescue
• Corymb unbranched, elongated with pedicles of
  uneven length forming inflorescence that appears
  flat apple
• Simple umbel peduncle bearing all pedicles at
  its apex onion
• Compound umbel cluster of simple umbels at apex
  of main axis carrot, dill
• Head peduncle with closely packed flowers
  without pedicles sunflower, daisy
• Catkin spikelike inflorescence bears only
  unisex flowers and only in woody plants - willow

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Sunflower

• Flower of sunflower is actually many individual
  flowers packed into a head

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Reproductive Morphology

• Promotes out-crossing and hybrid vigor
• form dictates function
• Most versatile plants have perfect flowers that
  are self-compatible can have successful
  reproduction within a single flower or flowers of
  same plant
• self-pollination transfer pollen from anthers
  to stigma on the same plant
• corn has 2 types of imperfect flowers on the same
  plant
• staminate flowers produce pollen but no ovules
  and are the tassels
• pistillate flowers produce ovules but not
  pollen corn cob that develop into fruit when
  pollen falls from the tassel onto the stigma of
  pistillate silk is the styles of the pistillate
  flower
• corn kernel is fruit

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Self-Fertilization vs Out-Breeding

• Staminate and pistillate flowers on the same
  plant are monoecius
• are considered in-breeding with sperm and egg in
  the same plant also called self-fertilization
• garden peas and snapdragons
• Staminate and pistillate flowers on different
  plants are dioecious
• this allows for fertilization by
  cross-fertilization as egg and sperm are on
  different plants
• leads to out-crossing
• mulberry, cottonwood and willow

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Other Methods of Fertilization

• Hoary plantain makes the carpels first and the
  stamens develop after carpels mature
• out-cross most often because pollen sheds from
  flower before pistil matures can also in-breed
  as plant gets older
• Garden peas can be in-bred or out-bred from the
  beginning, depends on which pollen gets to the
  stigma first

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Trade-Offs

• Self-pollination is efficient and can make seeds
  readily while cross-pollination is more risky
  no pollen brought in, then no seeds or offspring
• Most plants promote out-crossing because it
  yields hybrid vigor health and reproductive
  ability of offspring
• larger and more offspring
• self-pollinators are usually less vigorous and
  productive because of the in-breeding depression
• seeds produced vs likelihood that offspring are
  healthy and fertile
• Some plants with perfect flowers are
  self-incompatible while could self-fertilize
  the pollen never makes it to the egg

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Vegetative Reproduction

• Can induce plants from meristematic tissue to
  generate new plants these are clones
• Type of asexual reproduction as there is not
  sperm and egg involved
• strawberries and aspens are clones
• Advantage over sexual reproduction where
  pollination may be hard or production/germination
  of seeds is difficult
• humans exploit this

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Teddy-Bear Cactus

• Goes thru the motions of sexual reproduction but
  do not produce seeds
• Make flowers that develop into fruit without
  seeds, fall off and develop into a clone of the
  parent

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Definitions

• Systematics study evolutionary relationships
• Herbarium Collection of dried plant specimens
  arranged systematically for easy reference
• Floras plants of a given region collected into
  a book with detailed ecology and habitat of each
  plant

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Pollination by Animals Co-Evolved

• Example of mutualism both organisms benefit
  from the relationship
• Plants require the transfer of pollen from anther
  to stigma
• Flowers are highly adapted to specific type of
  pollen carrier
• interdependent, co-evolution of both pollination
  and mouth parts

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Attractants and Rewards

• Attractants color and odor of flower
• Rewards encourage pollinators to move from same
  kind of plant to another
• nectar is the big reward as well as pollen
• contains sugary liquid, some N-containing
  compounds

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Pollination by Wind

• Inefficient, yet common hard to get on stigma
  but easy to get on ground, water or noses to
  cause allergies
• Plants that pollinate this way produce large
  amounts of pollen grains to increase the odds
• plants have non-sticky pollen, no showy flowers
  or scents but have exposed stamen and large
  stigma, single ovule in each ovary, many flowers
  in each inflorescence

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Pollination by Water

• Very rare, few plants have flowers that are
  submerged under water such as sea grass
• In ribbon weed, the pollen is carried on little
  boats that slide into the flower in the water and
  catapult the pollen grains on the stigma

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Pollination by Insects

• Usually brightly colored, fragrant flowers
• Most common type of animal pollination
• Flowers are adapted for the different insects
  that pollinate bees are most common but wasps,
  flies, moths, butterflies, ants and beetles can
  also pollinate

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Special Features to Attack Specific Pollinator

• Nectar guides in UV light, petals are darker in
  the center to guide to the pollen
• Tubular or trumpet shaped flowers attract moths
  
• corolla has a landing pad for the moth to land on
  and crawl in the flower

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Special Features to Attack Specific Pollinator

• Carrion flowers drab and smell like rotting
  flesh, attracts carrion flies or beetles, thinks
  it is rotting flesh and lay eggs and transport
  pollen to next plant
• Animals obtain reward without pollinating
  nectar robbers prey on pollinating insects

4.
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Special Features to Attack Specific Pollinator

• Produce pheromones odor like a female wasp that
  brings in the male to copulate, in the process it
  picks up pollen to pass on
• called pseudocopulation

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Special Features to Attack Specific Pollinator

• Some flowers warm up and insects are attracted to
  the heat
• see in the sacred lotus heats over 5?C over air
  temp
• increase temperature by rapid cellular
  respiration give off as excess energy as heat
• Other mechanisms flowers follow sun, shiny disc
  shape that reflect sun to center
• usually very little nectar as reward rather than
  heat

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Other Animals Can Pollinate

• Some large flowers attract bats and small mammals
  can pollinate large flowers that are usually
  white and scented like fruit
• must be sturdy to sustain the small animal visits
  and enough nectar and pollen to fulfill the
  animals energy requirement

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Birds also Pollinate Flowers

• Hummingbirds are most common pollinators in North
  America and the honeycreeper in Africa/Asia
• Attracted to bright red flowers with no odors
• use long beaks to get to bottom of tubular
  corollas to get nectar
• Fuchias hang upside down and have an inferior
  ovary protects the ovary and ovules when beak
  enters the flower

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Fruit Develops from Ovary

• Seed container developed from the ovary and
  additional tissues around them
• Occurs only in flowering plants protects seeds
  and helps in dispersal
• Diversity of fruit types based on
  characteristics of mature ovary
• fleshy or dry
• ovary fused with other tissues
• both relate to how seeds are dispersed

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Dichotomous Key

• Use dichotomies 2 successive pairs of features
  at each of several steps to identify the fruits
  and plants

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Fleshy Fruit

• Often have 3 regions
• skin exocarp
• fleshy part mesocarp
• interior endocarp
• in apricot and peaches hard and stoney
• in tomato soft and moist
• All 3 make up the pericarp in stone fruits and
  tomatoes
• Mesocarp and endocarp are indistinct in some
  fruits

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Other Fruits

• Dry fruits all 3 are fused into one pericarp
  thin layer around the seed
• Accessory fruit flesh is expanded receptacle as
  in strawberries not derived from ovary
• Pomes apples are also accesory fruit
• Drupe usually have fleshy mesocarp however
  coconut is a drupe but the mesocarp is a fibrous
  husk
• only endocarp and large seed ends up on grocery
  shelf hard to separate endocarp from seed

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Coconut
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Aggregate Fruits

• Blackberry and magnolia
• blackberry individual ovaries develop into tine
  drupes and in magnolia develop into follicles
• Cob of corn is a multiple fruit but each kernel
  is a single fruit caryopsis or grin

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Dispersal of Fruit

• Fleshy fruit dispersed by hungry animals
• Dry fruit by wind or seed in fruit by wind
• usually have wings or hair to help disperse
• Hormones help fruit development seeds usually
  send out hormones for ovary development use
  artificial hormones to get synchronized harvest
  as in cotton and make fruit without fertilization
  seedless grapes

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Economic Value

• Floriculture business of growing/selling
  ornamental potted plants, flowers, fruits and
  seeds
• 4 billion in tulip sales in Netherlands, 20 of
  all its agriculture
• Flowers are a 8 billion business in USA of cut
  flowers, bedding plants, turf grasses and other
  plants
• Use flowers in making perfume, shampoo and
  lotions collected like we did spearmint oil

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Scents

• Perfume is 20 fragrant oil
• eau de toilette is 11 18 fragrant oil
• Cologne 5 10 fragrant oil