Inflorescences

Spring 2012

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,with maturation going from the base to the apex

Determinate inflorescencesFig. 9.35

cyme

scorpioid cyme

headhelicoid cyme

terminal &solitary

Indeterminate inflorescences

Fig. 9.36

spadixheadpanicle

raceme

spike

Determinate or indeterminate types

Fig. 9.37

Also heads can be either.

Secondary or compound inflorescence types

Fig. 9.38

Specialized inflorescence types

Fig. 9.39

Fruits

Spring 2012

Maturation

• An inflorescence matures into an infructescence.

• An ovary (simple or compound) matures into the fruit (but may include additional structures (e.g., hypanthium).

• 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)

pericarp

Avocado (Persea, Lauraceae)

seedseed

endocarpendocarp

mesocarpmesocarp

exocarpexocarp

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

Simple fruits

• Simple fruits = fruits developing from a single carpel or a compound ovary (2 or more fused carpels) (e.g., apple); 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 present?

Indehiscent Dry Fruits

Fig. 9.40

Achene: single-seeded, seed coat not fused to pericarp

Utricle – achene with the pericarp much larger than the seed

Caryopsis: “Grains”; singled-seeded, seed coat fused to pericarp; unique to grasses

Wheat (Triticum aestivum)

Maize (Zea mays)

Samara

Ulmus (Ulmaceae)

Dry Indehiscent Fruits: Nuts

hard-shelled,one-seeded

Dehiscent Dry FruitsFig. 9.41

Follicle: one suture opens

Asclepias (Milkweed, Apocynaceae)

Legume: opens along 2 sutures

Bean Family Fabaceae(Leguminosae)

Cruciferous Dry Fruits

Silique Silicle

Mustard Family (Brassicaceae)2-carpellate, outer rim (replum), persistent partition (false septum)

Capsule: a fruit formed from 2 or more united carpels and dehiscing at maturity to release the seeds

Loculicidal Capsule

Septicidal Capsule

Poricidal Capsule

Papaver (Poppy, Papaveraceae)

Schizocarp of mericarps

samaroid mericarpsAcer (Sapindaceae)

Dill (Apiaceae)

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 - Exocarp & mesocarp fleshy, endocarp hard (single-seeded)

• Pome – Fleshy mesocarp; exocarp fused to hypanthium/receptacle (Rosaceae)

Drupe

Drupe - Coconut

Cocos nucifera (Arecaceae)

Berry

Capsicum (Solanaceae)

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)

Pome

Rose family (Rosaceae): inferior ovary, cartilaginous endocarp, fleshy hypanthial tissue

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

Aggregate Fruit

Rubus(Rosaceae)

Aggregate of Achenes

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)