Lab #6B

Angiosperms

Flowers• structure of a flower – 4 rings of modified

leaves called flower organs:– 1. sepals– 2. petals– 3. stamens– 4. carpels

Stamen

Filament

Anther

Stigma Carpel

Style

Ovary

Petal

ReceptacleOvule

Sepal

1. Stigma2. Style3. Anther4. Filament5. Sepal

Perfect flowers

• male and female on same plant– lilies– dandelions– roses– virtually every fruit and vegetable plant in North America

• tomatoes

apple blossom

african violet

dandelion

Imperfect flowers

• male and female reproductive parts on separate flowers– but may be on the same plant– staminate flowers– carpellate flowers

staminate flowers

In fl o rescen ces

• inflorescences = group of cluster of flowers arranged on a stem that is comprised of a main branch or a complicated arrangement of branches

• several types– raceme - unbranched main

axis, flowers attached by a pedicel

– spike – unbranched main axis, directly attached flowers

– panicle – branched main axis– corymb– head (flower head) – also

known as a composite flower

Composite flowers

• composite flowers = clusters of many small flowers called florets – each of which is a full flower

• chicory, dandelion, chrysanthemum, yarrow, coreopsis, sunflower, dahlia, zinnia, goldenrod, aster, lettuce, thistle and Black-eyed Susan.

• composites are miniaturized flowers • numerous flowers packed onto a

platform called a receptacle,• so the sunflower is actually a

collection of hundreds of flowers!• two kinds of flowers: disk flowers and

ray flowers• disc flowers – center of the receptacle• ray flowers – surround the disc flowers

(look like petals) ray flowers

disc flowers

Flower ovules

Lilium ovary with ovules

Ovary with ovule

Ovary with ovules

Ovules

Ovule

Ovules

Anthers

Fruit

• composed of an outer wall = pericarp and the inner placenta with seeds– pericarp is made up of an exocarp, a

mesocarp and an endocarp• e.g. apple – skin = exocarp; flesh =

mesocarp; paper part in the center = endocarp; seeds

• classified as: simple, multiple or aggregate– simple – one carpel or several fused

carpels form the fruit• e.g apple

– multiple – more than one flower with female parts

– aggregate – number of separate carpels form the fruit

Fruits – dichotomous tree

• first division – fleshy or dry• I. Fleshy

– A. simple (from a single ovary) or B. complex (from more than one ovary)• A. simple- drupe (hard endocarp = cherry, olive, coconut), berry (fleshy

endocarp = tomato, grape, peppers, cucumbers), pome (apples, pears)• B. complex – aggregate (fruit from many carpels on a single flower =

strawberry, raspberry), multiple (fruit from carpels of many flowers fused together = pineapple, corn)

• II. Dry– A. fruits that split open at maturity (more than one seed) or B.

fruits that do not split (one seed)• A. fruits that split – along one seam (peas, beans and peanuts), along

multiple seams (okra, lilies, poppies)• B. fruits that don’t split – hard pericarp (acorns, chestnut), thin pericarp

and winged (maples, ash, elm), thin pericarp no wings (sunflowers, cereal grains, grasses)

Placentation

• ovules develop from the placenta and are attached to the ovary wall until maturation into seeds

• arrangement of the placenta = placentation– parietal – ovules on the outer ovary wall or extensions of it– free central – ovules along a central column or axis– axile – ovules along a central axis which is connected to the ovary wall

PlacentationAxile placentation Parietal placentation