The sexual reproductive structures
What is a flower?
• A flower is a highly modified shoot
bearing specialized appendages (modified
• Angiosperms are considered the
• Both monocots (ie grasses) and dicots
(ie petunias) flower.
• The floral stalk is
referred to as the
• The modified shoot
(or floral axis) is
called the receptacle.
• The perianth consists
of the outer
The perianth includes
the sepals and petals,
collectively known as
the calyx (sepals) and
• If the sepals and petals are distinctively
different in appearance, they continue to
be known as sepals and petals.
• If sepals and petals are undifferentiated in
appearance (ie many cactus flowers), they
are collectively described as tepals.
• The androecium
comprises all the
stamens of the flower.
Stamens are usually
differentiated into an
anther and a filament.
Each anther usually
contains four pollen
• Each anther usually contains four pollen
sacs, or microsporangia, which are
often confluent (joined) in two pairs.
• The pollen sacs are joined to each other
and to the filament by a connective.
• Pollen grains (microgametophytes) are
produced in the pollen sacs.
• The gynoecium
comprises all the
carpels of the flower.
Carpels are typically
composed of a
stigma, a style, and
an ovary (unique to
Locule and ovule
• The compartment, cavity, or chamber
within an ovary or anther is called a
• Ovule is the structure in seed plants
comprised of the female gametophyte.
After fertilization, it develops into the
• A nectary is a nectar-producing gland,
often forming projections, lobes, or
disklike structures. Nectaries are often
produced near the base of the androecium
and gynoecium. These are for the
production of nectar or other pollinator
attractants, such as oils or fragrances.
Three major parts of flowers
• Perianth (outer protective and/or colorful
• Androecium (pl. androecia) – pollen
• Gynoecium (pl. gynoecia) – ovule
• Has all three major parts (PAG)
• If one or more of the three major floral
parts (PAG) is missing, the flower is
considered to be incomplete.
Bisexual or perfect flower
• If at least the androecium and gynoecium
are present, the flower is termed bisexual
Unisexual or imperfect flower
• If either the androecium or gynoecium is
lacking, the flower is unisexual or
• If only the androecium is present, the
flower is considered staminate.
• If only the gynoecium is present, the
flower is considered carpellate.
• In a monoecious plant species, both
staminate and carpellate flowers are borne
on a single plant (ie pumpkins)
• In a dioecious plant species, the staminate
and carpellate flowers are borne on
separate individual plants (ie green ash)
• In a polygamous plant species, there are
both bisexual (perfect) and unisexual
(imperfect) flowers on the same plant.
• Perfect flowers have both androecium and
• Imperfect flowers are either staminate or
• Some flowers have an extra series of floral
parts, often showy, called coronas. These
may be outgrowths of the perianth parts,
stamens, or receptacles, and they are
extremely diverse in form and function.
• Radial Symmetry Two or more planes
bisecting the flower
through the center
These flowers are
• Bilateral symmetry
• Arranged so they can
be divided in
symmetrical halves on
only one plane.
These flowers are
• Asymmetrical –
• Flowers that have no
plane of symmetry.
Fusion of floral parts
• Connate – petals united to petals
• Distinct – petals distinct from each other
• Adnate – fusion of unlike parts like
stamens united to petals.
• Free – unlike parts are not fused.
Superior and inferior ovaries
• Flowers in which the perianth and androecium
are below the gynoecium are called
hypogynous. The ovary of such flowers is said
to be superior.
• Flowers in which the perianth and stamens
appear to be attached to the upper part of the
ovary are called epigynous. The ovary of such
flowers is said to be inferior.
Hypogynous and epigynous flowers