AngiospermsThe most advanced plant group

Jaime Crosby, CHS

General Characteristics of Flowering Plants

• Largest and most diverse division of plants with over 250,000 species– Can live in all biomes from desert to frigid

areas

• Definition: Seed in a vessel– The vessel is the carpel, the flower part

that becomes the fruit– Thus the seed is no longer naked, but

protected by a fruit• Anything with a seed is a fruit• Fruits: peppers, tomatoes, pumpkin, apples

Classification: 2 large classes

• Monocots– Leaves/petals in 3’s, one cotyledon

(seed leaf), parallel leaf veins, monkey faces, no wood rings

• Dicots– Leaves/petals in 4’s or 5’s, two

cotyledons, branched veins, ring of vascular bundles, possible tree rings

Views on origination

• Contemporary: believe angiosperms evolved independently from seed ferns, and the flower is a modified stem with modified leaf petals

• Traditional: believe angiosperms evolved from conifers and the flower is a modified cone

Life cycle of angiosperms…

• TREMENDOUS EVOLUTIONARY ADVANCEMENT…

• Structure of typical flower:

• Sepals enclose flower bud before opening– All sepals = calyx

• Petals attract insects and act as a landing pad– All petals = corolla

• Stamen = anther + filament– Inside the anther are the

microsporangia in which pollen is produced

• Pistil = Stigma + Style + Ovary– Female megagametophyte (ovule) is

produced here, fertilization occurs here, fruit develops here

Pollination

• Self or cross pollination– Most flowers produce sperm/eggs at

opposite times to avoid self-pollination

• Pollen grain lands on flower, form pollen tube toward ovary– Pollination by wind, water, insects,

birds and animals

• Double Fertilization: Each pollen grain contains 2 sperm; one sperm fuses with egg to form zygote, the other fuses with 2 polar nuclei to produce a triploid (3N) endosperm– Endosperm = food for the embryo in

the seed

• After fertilization, the seed forms, and the ovary wall thickens and becomes the fruit

• The seed becomes dormant until conditions are right for germination

• The seed absorbs water and the embryo grows a primary root and a cotyledon which will become the shoot

2 Vocab words about Angiosperms

• Parthenocarpy: fruits from unfertilized eggs like seedless watermelon, etc.

• Co-evolution: When 2 organisms evolve structures in response to each other– Hummingbirds and trumpet vines– Barbs, sweet fruits, etc.

• Velcro

Pollination ecology…

• Vectors– Bees use flower nectar as primary

nourishment• Prefer blue and yellow flowers with

honey guides which lead bees in• Ultraviolet patterns on flowers visible to

bees

• Flies– Dull red/brown colors– Foul “carrion” odors

• Moths/Butterflies– White or yellow colors– Sweet fragrances

• Beetles– Flowers generally white or dull color– Strong yeasty, spicy or fruity odors

• Birds– Flowers with bright red or yellow

inflorescences that produce copious amounts of nectar

– Tubular

• Bats– Tropical flowers that open at night

with ball-like flowers

Orchid Adaptations to welcome bees

• Pollinia sacs contain pollen– Stick to back/neck

• Petals modified to resemble female bees– Males try to mate

Angiosperm Bingo

• Cotyledon Triploid Fruit• Contemporary Traditional• Monocot Dicot Dispersal• Parthenocarpy Petals• Sepals Pollen tube• Germination Double Fert.• Pollination Yeasty, spicy• Carrion Yellow, blue, white, sweet• Pistil Stigma Style• Ovary Stamen Anther• Filament Corolla Calyx• 250,000 Velcro Integument• Endosperm Co-evolution