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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 - PowerPoint PPT Presentation
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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
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
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
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?
Caryopsis: “Grains”; singled-seeded, seed coat fused to pericarp; unique to grasses
Wheat (Triticum aestivum)
Maize (Zea mays)
Capsule: a dry fruit formed from 2 or more united carpels and dehiscing at maturity to release the seeds
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)
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(hesperidium)
Found in the citrus family (Rutaceae):Leathery exocarp, fleshy modified trichomes (juice sacs)
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
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