Flowers and Fruits

1
Chapter 12

• Flowers and Fruits

2
Flowers

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

3
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

4
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

9
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

13
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

14
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 carpels) and a gymnoecium (collection of
  stamens) 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