Download Angiosperm Reproductive Characters Evolution of Floral Structure

Angiosperm Reproductive
Characters
The flower and fruit are the
distinctive characters that define
Angiosperms
Evolution of Floral Structure
• Flowers are modified
shoots
– Branch with short
internodes
(receptacle)
– 4 Whorls of modified
leaves at nodes
1. Sepals (calyx)
2. Petals (corolla)
3. Stamens
(androecium)
4. Pistil = Carpel(s)
(gynoecium)
• + Nectaries
Presence/Absence of Parts I
• Complete Flower – All
4 whorls present
• Incomplete Flower –
one or more whorls
missing
• e.g., apetalous,
asepalous
1
Presence/Absence of Parts II
• Perfect Flower – All fertile parts present
(male & female) Hermaphrodite
• Imperfect Flower – One part missing
(male or female)
– Staminate flower – androecium only
– Pistillate flower – gynoecium only
– Dioecious – flowers on different plants
– Monoecious – flowers on same plant
Number of Flower Parts
• Most flowers have flower parts in multiples
of 3, 4, or 5. e.g.,
5 sepals, 5 petals, 10 stamens, 5 carpels (carpels
are often the exception to this rule)
• Monocots (lilies, grasses) are usually 3merous
• Dicots (broadleaf and woody) are typically
4-or 5-merous
Fusion of Floral Parts
• Parts of same embryonic origin
– Connate = fused (e.g, petals fused into a
tube)
– Distinct = unfused (separate)
• Parts of different embryonic origin
– Adnate = fused (e.g, stamens adnate to
petals)
– Free = unfused
2
Floral symmetry
• Radial = Actinomorphic,
Regular
– Equal size and spacing
of parts
– Can be cut any way into
mirror images
• Bilateral =
Zygomorphic, Irregular
– One line of
symmetry/divides flower
in half
– Only one way to cut into
mirror images
• Asymetrical = Neither
radial nor bilateral
– No plane of symmetry
(no way to cut equally)
Perianth Shapes Radial (regular)
• For Actinomorphic
Flowers (regular),
e.g.,
– Regular flower –
petals all look the
same with radial
symmetry
– Distinct petals
Perianth Shapes Radial (regular)
• Terms to Describe
Sympetalous
Corollas (tube, throat,
and limb [lobes])
Long-leaf Phlox
– corolla salverform- with a long
tube and abruptly flaring throat
and limb
3
Perianth Shapes
Bilateral (irregular)
• Common
Zygomorphic Corolla
shapes includes
– Bilabiate -upper and
lower lips (Figwort
family)
Perianth Shapes
Bilateral (irregular)
– Papilionaceous -with
standard, wings, keel
(typical of many peas)
Ligulate (Ray) -strap shaped
(sunflower family)
4
Androecium
• Male reproductive
parts
– Stamen = filament +
anther (with pollen)
Androecium
• Male reproductive
parts
– Epipetalous-stamens
adnate to corolla
– Connate stamens filaments fused into a
ring (monadelphous,
diadelphous, etc.)
Gynoecium
• Female reproductive
parts
– Pistil(s) composed of
one or more carpels
(Pistil = stigma, style,
and ovary with ovules)
– Simple ovary of one
carpel
– Compound ovary of
>1 connate carpels
5
Evolution of the Carpel
• From a leaflike
megasporophyll
• Megasporangia (ovules)
on margin
• Infolding enclosed ovules
• Syncarpous gynoecia
derived from fusion of
several simple
(apocarpous) pistils
• Stigma and styles may be
more or less fused
Walters and Keil, 1988
Ovary Position/Insertion of Parts
• Superior Ovary above other parts
– Hypogynous -other
parts inserted below
ovary
– Perigynous -other
parts fused into
hypanthium, with free
parts above ovary
6
Ovary Position/Insertion of Parts
• Inferior Ovary -below other parts
– Epigynous -other parts inserted above ovary, with or
without a hypanthium
7