Plants and People

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Plants and People

• Flowers

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Why a Flower?
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The Reproductive Structure of Flowering Plants
Perianth
Petal Corolla SepalCalyx
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Flower Anatomy
Calyx the outer whorl of sepals typically these
are green, but are petal-like in some species.
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Flower Anatomy
Corolla the whorl of petals, which are usually
thin, soft and colored to attract animals that
help the process of pollination. The coloration
may extend into the ultraviolet, which is visible
to the compound eyes of insects, but not to the
eyes of birds.
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Flower Anatomy
Androecium (from Greek andros oikia man's
house) one or more stamens, each with a filament
topped by an anther where pollen is produced.
Pollen contains the male gametes.
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Flower Anatomy
Gynoecium (from Greek gynaikos oikia woman's
house) all the female partsthe pistil(s) with
ovule(s) inside.
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Flower Anatomy
The basic unit of the female reproductive
structure is the carpel. Each physcial body is
called a pistil. A flower may have a single
carpel, which is a simple pistil (unicarpellate),
or several carpels united in one compound pistil
(syncarpous), or a cluster of un-united
carpels/pistils (apocarpous) The sticky tip of
the pistil, the stigma, is the receptor of
pollen. The supportive stalk, the style,
becomes the pathway for pollen tubes to grow from
pollen grains adhering to the stigma, to the
ovules, containing the gametes, housed inside the
ovary.
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Flower Anatomycarpel
carpel structure
fertilization
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Evolution of the Carpel
See figures 3.1 and 3.2 in your book
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Fruit and Seed Formation
A fruit develops from an ovary. A seed develops
from an ovule.
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Flower Structure Variation
perfect
imperfect
imperfect
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Flower Structure VariationOvary Position
A. ovary superior, floral parts hypogynous B.
ovary inferior, floral parts epigynous C. ovary
half-inferior D. ovary superior, floral parts
perigynous, hypanthium cup shaped
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Flower Structure Variation
A flower having sepals, petals, stamens, and
pistils is complete if a flower is lacking one
or more of these whorls, it is said to be
incomplete.
complete
incomplete
no stamens present incomplete
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Inflorescences
An inflorescence is a group or cluster of
flowers. It may be branched or unbranched.
Modifications can involve the length, variations
in the proportions, compressions, and swellings,
and the order in which the flowers open. Usually
the modifications have been evolved to optimize
the plants method of pollen dispersal.
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Inflorescences
raceme
spike
umbel
corymb
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Inflorescences
spadix
head
catkin
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Pollen Dispersal by Animals
Bees, Beetles, Bats, Birds, Butterflies, etc
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Symmetry
Flowers that are actinomorphic have "radial
symmetry", meaning they can be divided into
symmetrical halves by more than one longitudinal
plane passing through the axis, much as a pie can
be cut into several equal and identical pieces.
Zygomorphic flowers are "yoke shaped or
have"bilateral symmetry, where flowers can be
divided by only a single plane into two
mirror-image halves, much like a yoke or a
person's face.
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Dicot versus Monocot
Dicot
Monocot
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Lab Objectives

• 1. Flowers are arranged in groups called
  inflorescences. We will examine some
  inflorescences particular to certain families
  later in the semester. For now, know what an
  inflorescence is and which ones we looked at
  today.
• 2. DRAW a longitudinal section of a typical
  flower labeling the following parts receptacle,
  calyx, sepals, corolla, petals, perianth,
  pedicel, ovary, ovule, style, stigma, pistil,
  gynoecium, anther, filament, stamen, and
  androecium.
• 3. EXAMINE by dissection the floral material
  provided making long and cross sections of the
  flower and its parts. On a separate sheet of
  paper, SKETCH the flowers and label the parts.
  Then, FOR EACH FLOWER, answer the following
  questions
• A. Is the flower actinomorphic (regular) or
  zygomorphic (irregular)?
• B. How many sepals are present? Petals?
  Stamens? Carpels? To count carpels, count the
  locules, styles, style branches, and/or the
  zones of placentation by cross- sectioning the
  ovary.
• C. Is the ovary inferior or superior?
• D. Is the flower from a monocotyledonous or
  dicotyledonous plant?
• E. Is the flower perfect (both sexes present)
  or imperfect? Complete (all four floral whorls)
  or incomplete?

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