Inflorescences & Fruits

Spring 2010

What is an inflorescence?

• Harris & Harris = The flowering part of a plant; a flower cluster; the arrangement of flowers on the flowering axis

• Judd et al. = The shoot system which serves for the formation of flowers and which is modified accordingly

Look for the flowering zone!

Fig. 4.27 from the text

Fig. 4.28 from the text

Determinate Determinate inflorescencesinflorescences

Fig. 4.29 from the text

cyme

umbel

scorpioid cyme

headhelicoid cyme

terminal &solitary

IndeterminateIndeterminateinflorescencesinflorescences

Fig. 4.30 from the text

spadixheadpanicle

spike

raceme

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

Fig. 4.31 from the text

Fruit diversity

Simple vs. multiple fruits

• Simple fruit = a fruit that develops from a single flower

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

Simple fruits: two types

• “Simple” simple fruits = fruits developing from a single carpel or a compound ovary (2 or more fused carpels) (e.g., apple)

• Aggregate simple fruits = fruits developing from several separate carpels of a single gynoecium (e.g., blackberry)

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?

Follicle: one suture opens

Asclepias (Milkweed, Apocynaceae)

Legume: opens along 2 sutures

Bean Family Fabaceae(Leguminosae)

Cruciferous Dry Fruits

Silique Silicle

Mustard Family Brassicaceae (Cruciferae)

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)

Indehiscent Dry Fruits

Samara

Acer (Sapindaceae)

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

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

Wheat (Triticum aestivum)

Maize (Zea mays)

Dry Indehiscent Fruits: Nuts

hard-shelled,one-seeded

Fleshy Fruits

One or more layers of the pericarp

become fleshy; may be brightly colored.

If the ovary is inferior, then the hypanthium may also be involved and it may be the conspicuously fleshy part of the fruit.

Fleshy Fruits

• Berry – Entire pericarp fleshy or exocarp may be leathery, one to many seeds

• Drupe - Exocarp & mesocarp fleshy, endocarp hard

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

Berry

Capsicum (Solanaceae)

Berry

Berry (Pepo)

Found in the Cucumber Family (Cucurbitaceae)

Berry(hesperidium)

Found in thecitrus family(Rutaceae)

Drupe

Drupe - Coconut

Cocos nucifera (Arecaceae)

Pome

Aggregate Fruit

Rubus(Rosaceae)

Multiple Fruit - Pineapple

Ananas (Bromeliaceae)

Multiple Fruit: Syconium (Fig)

Ficus (Moraceae)

Accessory fruits

Fruit or cluster of fruits in which structuresin addition to the matured gynoecium forma functional part of the fruit.

Simple accessory fruit: e.g., strawberry

Multiple accessory fruit: e.g., pineapple

Accessory “Fruit” – Aggregate of Achenes