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 = 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

Determinate inflorescences Fig. 9.35

From: nickrentlab.siu.edu

cyme scorpioid cyme head helicoid cyme terminal & solitary

Indeterminate inflorescences Fig. 9.36

spadix head panicle raceme spike

Determinate or indeterminate types Fig 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 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 endocarp mesocarp exocarp

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”; 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 Fruits Fig. 9.41

Follicle: one suture opens Asclepias (Milkweed, Apocynaceae)

Follicles in the Ranunculaceae (buttercup family)

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 samaroid mericarps Acer (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 - 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 blueberriestomatoes eggplants bananas 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 A. Laurent Platanus (sycamore)

Multiple Fruit - Pineapple Ananas (Bromeliaceae)

Multiple Fruit: Syconium (Fig) Ficus (Moraceae)