Lab 2: Angiosperm Flowers: Lab 2: Angiosperm Flowers Biology 101 Spring 2005


Life problems addressed this week: Life problems addressed this week How do plants reproduce when they can’t move from place to place?


Recall Life Cycles in Angiosperms: Recall Life Cycles in Angiosperms Plants alternate between the sporophyte generation (2n) and the gametophyte generation (n) during their life cycles The mature plant we see in Angiosperms is the sporophyte or diploid generation The female gametophyte develop and are retained within the parent plant, the male gametophytes are pollen grains


Angiosperm Life Cycle: Angiosperm Life Cycle


Basic Flower Structure: Basic Flower Structure


Flower Structure: Flower Structure A specialized shoot with four circles of modified leaves: sepals, petals, stamens, and carpels At the bottom of the flower are the sepals, which are usually green and enclose the flower before it opens, they are sterile Above the sepals are the petals, which are brightly colored in most flowers (but not usually wind pollinated ones), they are also sterile The stamens and the carpels are fertile leaf derived floral parts


Flower Pollination: Flower Pollination Flowers may be pollinated by wind or one of several different types of animals; insects, birds, or mammals Flower structure reflects pollination scheme Some flowers self-pollinate but more often have a structure that ensures cross-pollination


Wind Pollinated Flowers: Wind Pollinated Flowers Flower color usually dull Usually no odor Many tiny flowers Common in plants that occur in dense populations


General Insect Pollinated Flowers: General Insect Pollinated Flowers Flower color usually bright often yellows to blues, poor in reds, often UV patterning Fresh and/or sweet odor Flowers usually have a flat platform like arrangement


Bee Pollinated Flowers: Bee Pollinated Flowers Variable yellows, blues, but not red, often UV patterning Strong sweet odors Often sturdier flowers with fused arrangements that causes bee to brush against pollen while forcing its way in


Bird Pollinated Flowers: Bird Pollinated Flowers Flowers often reddish, birds have excellent vision from red to violet No odors Large nectaries, often places for the bird to perch which also facilitate pollination


Mammal Pollinated Flowers: Mammal Pollinated Flowers Flower color often dull (many mammal pollinators are nocturnal), but not always Highly fragrant flowers, not always sweet Flowers large, often sturdy with a heavy stem when pollinated by mammals other than bats


Pollen Tube Growth: Pollen Tube Growth


Life problems addressed this week: Life problems addressed this week How do plants reproduce when they can’t move from place to place? Flower structure facilitates pollination which gets the male gametophyte near the female gametophyte, then pollen tube growth completes the process


Part II: Part II A TA’s Guide to Flowers Used in Lab


Geraniums: Geraniums Very basic flower plan Stigmas and anthers are not mature at the same time (helps prevent self-fertilizations) Insect generalist UV patterning Syncarpel of five fused carpels (count the lobes)


Snapdragon: Snapdragon Heavy lower petal supports a bee and only opens to a forceful insect insuring the correct pollinator Similar to the orchid because they are both pollinated by large bees Pollen rubs onto bee’s back


Orchid: Orchid Sepals are colored in the orchid Has a column (fusion of stamens and carpel(s) into one structure Is a monocot Heavy lower petal called a labellum


Milkweed: Milkweed Part of a cluster of flowers called an inflorescence As insect moves over the flower, leg slips and gets caught on corpusculum of pollinium Pollinia then get stuck in the slits with the stigma


Sunflower: Sunflower Composite flower composed of ray florets and disc florets Ray floret is sterile, one petal and a few sepals Disc floret is fertile Disc florets mature at different times preventing self-fertilization


Bird of Paradise: Bird of Paradise Boat-shaped bract called the spathe holds the inflorescence Blue “arrowhead” formed by modified petals, when bird lands, exposes the anthers At the base of “arrowhead” a third petal forms the deep nectary


Poinsettia: Poinsettia Red showy structures are not petals, actually specialized leaves called bracts Actually an inflorenscence, flowers are small round in the middle and they aren’t even technically single flowers Nectary for birds


Sugarbush (Protea): Sugarbush (Protea) Bloom close to ground so can be pollinated by rodents Hearty flower and heavy stem help support weight of rodent Inflorescence with large showy bracts


Wheat: Wheat Wind pollinated Inflorescence of many small pollen laden flowers Bracts enclose the flowers Not showy, scented, or colored