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 inflorescences Fig. 9.35

scorpioid cyme cyme terminal & solitary head helicoid cyme

Indeterminate inflorescences Fig. 9.36

raceme spike spadix head panicle

Determinate or indeterminate types Also heads can be either. Fig. 9.37

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

exocarp mesocarp endocarp seed Avocado (Persea, Lauraceae)

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 Fruits Fig. 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 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 - 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 Platanus (sycamore) A. Laurent

Multiple Fruit - Pineapple Ananas (Bromeliaceae)

Multiple Fruit: Syconium (Fig) Ficus (Moraceae)