Flowers and Arabidopsis thaliana

Carpel

female egg producing reproductive organ of a flower which contains the stigma, style, ovary, and ovules

Stigma

where pollen sticks/attaches to

Style

the long tube that connects the stigma to the ovary

Ovary

BECOMES THE FRUIT

enlarged structure at the base of carpel where the ovules are located

Ovules

BECOMES THE SEED

contains egg or female gametophyte

Stamen

male pollen producing final organ which consists of the anther, filament, and pllen

Anther

part of the stamen that produces pollen

Filament

stalk like structure that holds the anther

Pollen

contains sperm nuclei & is the immature male gametophyte

Petals

whorl of flower organs that are often brightly colored to attract pollinators

Corolla

whorl of petals in a flower

Sepals

whorl of leaf like organs outside the corolla; help protect the unopened flower bud

Calyx

whorl of sepals in a flower

Pollination

the transfer of pollen from the anther to the stigma (from one flower to another not in the same flower)

Perfect flowers

flowers that have both sperm & egg producing parts (have stamen and carpels)

Complete flowers

flowers that have all four organs (sepals, petals, stamen, and pistils/carpels)

Incomplete

flowers that are missing any one or more floral organs (sepals, petals, stamen, and pistils/carpels)

True

a flower can be perfect but incomplete

Timing, morphological, and biochemical

types of strategies that flowers use to avoid self-pollination

Coevolution

Interactions between two different species as selective forces on each other, resulting in adaptations that increase their interdependency

ex: animal flowering plant interactons

Bees

-Live on the nectar and feed larvae, also eat the pollen

-Guided by sight and smell

-See yellow and blue colors and also ultraviolet light (not red)

-Flowers have “honey guides” and bee landing platforms

Butterflies and moths

-are also guided by sight and smell

-for one of the insects, they can see red an orange flowers

-for one of the insects, flowers are usually shaped as a long tube b/c of insect’s proboscis so that those insects can get to the nectar

-for the other of the insects, flowers are usually white or pale with sweet strong odor for night pollination

Flies

like flowers that smell like dung or rotten meat because they lay their eggs there

but their larvae die due to lack of food

Beetles

pollinate flowers that are dull in color, but have very strong odor

Birds

-Have a good sense of color and like yellow and red flowers

-Don’t have a good sense of smell, so flowers for them usually have little odor

-the flowers they pollinate provide fluid nectar in greater quantities than insects

-the flowers may have long, tubular corolla

-Pollen is large & sticky

Bats

flowers are white for night pollination

Mice

flowers pollinated by these animals are usually inconspicuous and open at night

Arabidopsis thaliana

-a small plant in the mustard family related to broccoli, cabbage, & cauliflower

-a model system of choice/plant “guinea pig” for research in plant biology

-important scientific discoveries in understanding plant growth & development have been made by focusing on the molecular genetics of this plant

-Easy to grow and is short

-Has a short life cycle of about 6-8 weeks and has a small genome

ABC model for plant development

shows that 3 genes are involved in the formation of flower organs and was discovered by doing deletion mutations

Rings 1 and 2

Gene A

Rings 2 and 3

Gene B

Rings 3 and 4

Gene C

A only = sepals

Ring 1

A & B = petals

Ring 2

B & C = stamens

Ring 3

C only = carpels

Ring 4

carpel, stamen, stamen, carpel

Mutant without gene A expression

Sepal, sepal, carpel, carpel

Mutant without gene B expression

Sepal, petal, petal, sepal

Mutant without gene C expression

Carpel, carpel, carpel, carpel

Mutant without A and B

Sepal, sepal, sepal, sepal

Mutant without B and C

all leaves

Mutant without A, B, or C expression

Important scientific discoveries in Arabidopsis

Flower development, photoreceptors in plants, phototropism, gravitropism, plant pathogen interactions, mechanisms of plant hormone action, and more