Anthophyta (part 2)

flowers and fruits

Outline

Flowers

structure

four floral whorls attached to receptacle

1. sepals
2. petals
3. stamens = anther + filament
4. carpel(s) [=pistil(s)] = ovary + style + stigma

terminology

• calyx = sepals collectively
• corolla = petals collectively
• perianth = corolla + calyx

placement of ovary may vary

• hypogynous flowers have a superior ovary
• epigynous flowers have an inferior ovary
• perigynous flowers have a cup-shaped receptacle surrounding the ovary

some flowers lack one or more floral whorl:

• incomplete vs. complete flowers
• perfect vs. imperfect flowers
  • staminate vs. pistillate imperfect flowers

some plant species are dioecious

dioecious species have individuals that either male or female

their plants have either staminate or pistillate imperfect flowers

monoecious species have individuals that are both male and female

their plants have:

1. both staminate and pistillate imperfect flowers on same plant, or
2. perfect flowers

evolutionary trends

early flowers	modern flowers
radially symmetry	bilaterally symmetry (in some)
many parts in each whorl, often an indefinite number	reduced number of floral parts
receptacle relatively long	shortened receptacle, some fusion of floral parts (w/in whorl or between whorls)
superior ovary	inferior ovary (in some)
insect pollinated (beetles)	wind pollination in some, other insects etc. performing pollination

pollination

considerations

pollinators

plant as food source: eat pollen, drink nectar

plants must:

• prevent excessive pollinator herbivory (closed carpels)
• keep pollinator from going home sated -- offer limited reward
• keep pollinator within species

many plants have specialized on a kind of pollinator

floral syndromes -- flower morphologies associated with specific kinds of pollinators. Depend on senses, flying abilities, morphology, intelligence and behavior of animal

beetles -- "mess and soil" pollination

pollinator	flower
poor vision good sense of smell poor fliers hairy, good chewers, eat pollen & nectar stupid diurnal	color dull, white large, bowl-shaped strong, fruity or carrion odor inferior ovaries e.g., wild roses, Magnolia, Queen Anne's lace (wild parsley)

butterflies

pollinator	flower
good vision (UV) poor sense of smell good fliers, land to feed drink nectar with long proboscis diurnal	reds, oranges, blues with nectar guides often in UV flat-topped, vertical, with long tubular corollas fresh, agreeable smell close up e.g., milkweeds

moths

pollinator	flower
poor vision good sense of smell good fliers, hover when feeding hairy, drink nectar with long proboscis nocturnal	color white long tubular corollas, often presented horizontally strong, perfumey odor, often only after dark e.g., Nicotiana (like petunias)

bees

pollinator	flower
good vision (UV), can't see red poor sense of smell good fliers, land to feed hairy, eat pollen & nectar intelligent diurnal	yellow, blue, white often with nectar guides often in UV landing platform, sometimes the lip of bilaterally symmetrical flowers mild, fresh smell e.g., [MANY flowers] orchids, snapdragons, sunflowers, etc.

birds and bats -- analogous to butterflies and moths, except:

• they are larger and "warm-blooded," so they have greater energetic rewards
• most hummingbirds hover when feeding, especially like red
• bats eat nectar and pollen

promotion of outcrossing -- preventing self-pollination

some plants prefer selfing -- weeds, tundra plants

most have adaptations to prevent it:

• being dioecious
• dichogamy -- e.g., protrandry
• physical arrangement of anthers and stigma
• genetic self-incompatibility

Fruits

structure

classification of fruits

according to state at maturity:

• fleshy
• dry

according to tissues that give rise to it:

• "true" -- ovary wall only
• accessory -- other tissue

according to complexity:

• simple
• aggregate
• multiple

function

protection of seeds

dispersal of seeds

explosive fruits

wind -- dandelions, maples,

water -- coconuts and some sedges

animals

external & involuntary

• hooks and glue
• burdocks, beggar's ticks etc.

internal & voluntary

• most fleshy fruits do this
• plants advertise when fruit is ripe/seeds are mature
  • unripe: green, unpalatable: astringent/sour/hot/toxic
  • ripe: red or other color, palatable: tasty/sweet/juicy/smelly
• seeds are digestion-resistant, fruits have laxative properties

voluntary (external) by gatherers

• acorns/squirrels
• elaiosomes/ants

Vocabulary

click here to go to angiosperm vocabulary