Inflorescences

Spring 2013

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 flowerbut rather retains its meristematic potential,with maturation going from the base to the apex

Determinate inflorescencesFig. 9.35

cyme

scorpioid cyme

head helicoid cyme

terminal &solitary

Indeterminate inflorescences

Fig. 9.36

spadixheadpanicle

raceme

spike

Determinate or indeterminate types

Fig. 9.37Also heads can be either.

Secondary or compound inflorescence types

Fig. 9.38

Specialized inflorescence types

Fig. 9.39

Fruits

Spring 2013

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

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.

pericarp

Avocado (Persea, Lauraceae)

seed

endocarpmesocarp

exocarp

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

• Multiple fruit = a fruit derived from the gynoecia of several closely clustered flowers

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”; singled-seeded, 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

Dehiscent Dry FruitsFig. 9.41

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 separatealong 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

samaroid mericarpsAcer (Sapindaceae)

Dill (Apiaceae)

Fleshy Simple Fruits

One or more layers of the pericarpbecome 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 tomatoes

eggplantsbananas 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

• Multiple fruit = a fruit derived from the gynoecia of several closely clustered flowers

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

• Multiple fruit = a fruit derived from the gynoecia of several closely clustered flowers

Multiple fruit of achenes

A. Laurent

Platanus (sycamore)

Multiple Fruit - Pineapple

Ananas (Bromeliaceae)

Multiple Fruit: Syconium (Fig)

Ficus (Moraceae)