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Flowers
Flowers
• Functions
• Specialized Shoots Bearing
Reproductive Organs
• Typically Composed of 4 Whorls of
Highly Modified Leaves Called Floral
Organs
• Determinate Shoots
Symmetry
• How Many Directions Can You Slice Flowers & Have Them Form
Mirror Images?
• Actinomorphic
—Star Shaped
—Radially Symmetrical
• Zygomorphic
—Not Radially Symmetrical
Pollinators
• Bees
• Hummingbirds
• Bats
• Wasps
• Flies
• Moths
• Other?
MONOCOTS
DICOTS
Embryo With single
cotyledons
Pollen With single furrow or
pore
Flower parts in multiples of
three
Major leaf veins parallel
Stem vascular bundles
scattered
Roots are adventitious
Embryo With two
cotyledons
Pollen With three furrows
or pores
Flower parts in multiples of
four or five
Major leaf veins reticulated
Stem vascular bundles in a
ring
Roots develop From radicle
Secondary growth absent
Secondary growth Often
Flower Parts
• Some Flower Parts Are Not Essential
–Sepal
• Structure Which Usually Forms the Outermost Whorl of the Flower
• Collectively, the Calyx
– Petals
• Dicot Accessory Flower Structures
• Usually Whorled Floral Structures Which Collectively Make Up the
Corolla
• They Protect the Inner Reproductive Structures
• Often Attract Insects By Their Color or Nectar
• Thus Facilitate Pollination
• Perianth
– Non-Reproductive Parts of the Flower
Essential Flower Structures
• Stamen (Male Flower)
–Anther (Produces Pollen)
–Filament (Stalk to Support
the Anther)
• Androecium (All Stamens)
• Pistil (Female Flower)
–Stigma (Receives Pollen)
–Style (Connects Stigma to
Ovary)
–Ovary (Contains the Egg & 1 or
More Ovules)
–Gynoecium (All Pistils)
• Nectaries at Base of Perianth
–Produce Sticky, Sugary Substance, Attract Pollinators
• Receptacle
–The Enlarged Apex of the Pedicel Into Floral Parts Arise
–Supports the Flower
–Strawberry
• The Fleshy Portion
–Apple
• Ovary Is Recessed Into the Receptacle
• Rachis
–Main Axis or Shaft
• Main Stem of Inflorescence
• Stalk of a Compound Leaf
• Cluster of Grapes
• Head of Wheat
• Pedicel
–Supports an Individual Flower in an Inflorescence
• Peduncle
–Floral Axis
–Stalk That Connects a Flower to the Stem
–Single Flowers or Inflorescences
• Bracts
–Modified Leaves That Replace the Calyx & Corolla
Flower vs. Inflorescence
• Flower
–Reproductive Structure Found
in Angiosperms
• Inflorescence
–Collection of Individual
Flowers on a Main Stem
http://www.lib.ksu.edu/wildflower/drawing/inflorescence.jpg
Types of Inflorescences
• Spike
–Flowers Attached Directly to Rachis
–Sessile
• Flowers Attached Directly to Rachis Without a
Pedicel
• Raceme
–Just Like Spike Except Raceme Has Pedicels
–Flowers Are Pedicellate
• Panicle
–A Branched Raceme
–Each Branch Bears a Further Raceme of
Flowers
–Flowers May Be Sessile or Pedicellate
• Corymb
–Pedicles of Different Lengths Attach at
Different Locations on Axis to Create a
Flat-Topped Inflorescence
• Umbel
–Has No Central Axis
–All Pedicles Attach at the Same Point at
Base of Inflorescence
–
• Head
–Many Sessile Flowers That Are Tightly
Clustered on a Flattened Receptacle
–Two Types of Flowers
• Ray
• Disk
• Capitulum
–Similar to Head Inflorescence Except the Head Is Rounded
–Flowers Can Be Either Sessile or Pedicellate
–eg: Red Clover or White Clover
• Catkins
–Slim, Cylindrical Flower Cluster, Inconspicuous or No Petals
–Usually Wind-Pollinated, Sometimes Insects
Grass Flower
• Spikelet
– Individual Flowering
Unit of Grasses
– Spikelet Contains
1. Glumes
2. Rachilla
3. Florets
4. Lemma
5. Palea
6. Lodicules
7. Pistil
8. Stamens
1. Glumes
– 2 Leaflike
Bracts at Base
of Spikelet &
Enclose the
Rest of Spikelet
2. Rachilla
– The Central
Axis of the
Spikelet
– It Is a StalkLike Structure
That Connects
All the Florets
3. Florets
– 1 or More per
Spikelet
– Contain
Stamens &
Pistil With
Other Bracts
– Uppermost
Floret Usually
Undeveloped
& Sterile
4. Lemma
– The First Bract at
the Base of the
Floret
– Its Tip Is Called the
Awn
5. Palea
– A Bract Located Just
Above & Opposite
the Lemma
– Together the Lemma
& Palea Enclose the
Stamens & Pistil
6. Lodicules
– Very Small
Bracts at
Base of Pistil
– Serve No
Known
Function
Except for
Identification
7. Pistil
– The Female Organ
of the Plant
8. Stamens
– The Male
Reproductive
Organs of the
Plant
– In Monocots, the
Stamens Occur in
Multiples of 3
– Most Grasses Have
3 Stamens
Plant Sex!
• Complete Flower
–Contains All 4 Flower Parts
• Sepals
• Petals
• Pistil
• Stamens
• Incomplete Flower
–Missing 1 or More of These Parts
• Perfect Flowers
–Contain Both the Stamens & Pistil
• Imperfect Flowers
–Are Missing Either the Stamens or Pistil
–Monoecious vs. Dioecious
• Pistillate Flower
–Has Only Female Flower Parts
• Staminate Flower
–Has Only Male Flower Parts
• Monoecious Plants
–“One House”
–Pistillate Flowers & Staminate Flowers on the Same Plant
–eg: Corn, Begonia
• Dioecious Plants
–“Two Houses”
–Only Staminate or Pistillate Flowers
–eg: Buffalograss, Holly
• Synoecious Plants
–Contain Perfect Flowers
• Hypanthodium
–Spherical Receptacle With Cavity Inside
–Numerous Small Sessile Flowers on Inner Surface
–Most Self-Pollinating
–Explodes Seeds Everywhere