Inflorescences
Spring 2014
What is an inflorescence?
• Simpson = An aggregate of one or
more flowers, the boundaries of
which generally occur with the
presence of vegetative leaves below
• Judd et al. 2008 = The shoot system
which serves for the formation of
flowers and which is modified
accordingly
Look for the flowering zone!
(from Judd et al. 2008)
Inflorescence development
Determinate: the apical meristem of the primary
inflorescence axis terminates in a flower, which
usually matures first with overall maturation from
the apex to the base
Indeterminate: the apical meristem of the primary
inflorescence axis does not terminate in a flower
but rather retains its meristematic potential,
with maturation going from the base to the apex
Fig. 9.35
Determinate inflorescences
From: nickrentlab.siu.edu
scorpioid cyme
cyme
terminal &
solitary
head
helicoid cyme
Indeterminate inflorescences
Fig. 9.36
raceme
spike
panicle
head
spadix
Determinate or indeterminate types
Fig. 9.37
Also heads can be either
determinate or indeterminate.
Secondary or compound inflorescence types
Fig. 9.38
Specialized inflorescence types
Fig. 9.39
Fruits
Spring 2014
Maturation
• An inflorescence matures into an
infructescence.
• An ovary (simple or compound) matures
into the fruit (but may include additional
structures (e.g., hypanthium or perianth
parts).
• A fertilized ovule matures into a seed.
Ovary wall becomes the pericarp:
•
ENDOCARP – innermost layer
•
MESOCARP - middle layer
•
EXOCARP - outermost layer
pericarp
Each can be modified independently of the others
(e.g., the endocarp can be stony, the mesocarp fleshy,
and the exocarp leathery) or the pericarp can be of
uniform color or texture.
exocarp
mesocarp
endocarp
seed
Avocado
(Persea, Lauraceae)
Three main fruit groups
• Simple fruit = a fruit that develops from a
single flower with a single simple or
compound pistil
• Aggregate fruit = develops from multiple
separate carpels (pistils) of a single flower;
unit fruit is what develops from one carpel
• Multiple fruit = a fruit derived from the
gynoecia of several closely clustered flowers;
unit fruit comes from one flower
Simple fruits
• Simple fruits = fruits developing from
the gynoecium of a single flower (i.e.,
a single carpel or a compound ovary
of 2 or more carpels); can be dry or
fleshy
Dry Simple Fruits
• Dry at maturity
• Does fruit open (dehisce) or not?
(Dehiscent versus indehiscent)
• Number of carpels?
Number of seeds?
• Are any wings or other appendages
present?
Indehiscent Dry Fruits
Fig. 9.40
Achene: single-seeded, seed
coat not fused to pericarp
Utricle – a bladdery or inflated achene
with the pericarp larger than the seed
Caryopsis: “Grains”; singledseeded, seed coat fused to
pericarp; unique to grasses
Wheat
(Triticum aestivum)
Maize (Zea mays)
Samara — a single-seeded, dry,
winged indehiscent fruit
Ulmus (Ulmaceae)
Dry Indehiscent Fruits: Nuts
hard-shelled,
one-seeded
Fig. 9.41
Dehiscent Dry Fruits
Follicle: one suture opens
Asclepias (Milkweed, Apocynaceae)
Follicles in the
Ranunculaceae
(buttercup family)
http://tezalizard.blogspot.com
Legume: opens along 2 sutures
Bean Family
Fabaceae
(Leguminosae)
Capsule: a dry fruit formed from 2
or more united carpels and
dehiscing at maturity to release
the seeds
Loculicidal Capsule
Each carpel splits along the middle,
opening directly into the locule
Septicidal Capsule
The carpels
separate
along their
side walls,
or septa.
Poricidal Capsule
Papaver (Poppy, Papaveraceae)
Capsule modifications
In some plant families, capsules are
modified in special, characteristic ways.
Fruit and seed dispersal are still the
guiding needs.
Cruciferous Dry Fruits
Silique
Silicle
Mustard Family (Brassicaceae or Cruciferae)
2-carpellate, outer rim (replum), persistent
partition (false septum)
Schizocarp of mericarps
Dill (Apiaceae)
samaroid mericarps
Acer (Sapindaceae)
Fleshy Simple Fruits
One or more layers of the pericarp
become fleshy—which one(s)?
Number of carpels? Number of seeds?
From a superior or inferior ovary?
Fleshy Simple Fruits
• Berry – Entire pericarp fleshy or exocarp
•
•
may be leathery; one to many seeds
Drupe - Mesocarp fleshy, endocarp
hard, exocarp variable; usually one
seeded but can have multiple seeds
Pome – Fleshy mesocarp (mainly
hypanthium tissue) and leathery or
papery endocarp; derived from an
inferior ovary (Rosaceae)
Berry
Capsicum (Solanaceae)
Berry—other examples
blueberries
bananas
eggplants
tomatoes
tomato
relatives
Berry (Pepo)
Found in the
Cucumber Family
(Cucurbitaceae):
parietal placentation,
leathery exocarp
Berry
(hesperidium)
Found in the citrus
family (Rutaceae):
Leathery exocarp, fleshy
modified trichomes
(juice sacs)
Drupe—stony endocarp
Drupe - Coconut
Cocos nucifera
(Arecaceae)
Pome
Rose family (Rosaceae): inferior ovary, cartilaginous
endocarp, fleshy hypanthial tissue
Three main fruit groups
• Simple fruit = a fruit that develops from a
single flower
• Aggregate fruit = develops from multiple
separate carpels of a single flower; unit fruit
is what develops from one carpel
• Multiple fruit = a fruit derived from the
gynoecia of several closely clustered flowers;
unit fruit comes from one flower
Aggregate
Fruit
Rubus
(Rosaceae)
Aggregate of Achenes
Aggregate of samaras
Three main fruit types
• Simple fruit = a fruit that develops from a
single flower
• Aggregate fruit = develops from multiple
separate carpels of a single flower; unit fruit
is what develops from one carpel
• Multiple fruit = a fruit derived from the
gynoecia of several closely clustered flowers;
unit fruit comes from one flower
Multiple fruit of achenes
Platanus (sycamore)
A. Laurent
Multiple Fruit - Pineapple
Ananas (Bromeliaceae)
Multiple Fruit: Syconium (Fig)
Ficus (Moraceae)