KEY CONCEPT Reproduction of flowering plants takes place within flowers.

Flowers contain reproductive organs protected by specialized leaves. Sepals and petals are modified leaves. Sepals are outermost layer that protects developing flower sepal

Petals can help to attract animal pollinators

A stamen is the male structure of the flower. filament anther anther produces pollen grains filament supports the anther

The innermost layer of a flower is the female carpel. style stigma ovary stigma is sticky tip style is tube leading from stigma to ovary ovary produces female gametophyte

Flowering plants can be pollinated by wind or animals. Flowering plants pollinated when pollen grains land on stigma. Wind pollinated flowers have small flowers and large amounts of pollen.

Animal pollinated flowers have larger flowers and less pollen. many flowering plants pollinated by animal pollinators pollen grains pollination occurs as animal feeds from flower to flower animal pollination more efficient than wind pollination

Fertilization takes place within the flower. Male gametophytes, or pollen grains, are produced in the anthers. male spores produced in anthers by meiosis each spore divides by mitosis to form two haploid cells two cells form a single pollen grain pollen grain

One female gametophyte can form in each ovule of a flower’s ovary. four female spores produced in ovule by meiosis one spore develops into female gametophyte female gametophyte contains seven cells one cell has two nuclei, or polar nuclei one cell will develop into an egg

Pollination occurs when a pollen grain lands on a stigma. pollen tube sperm stigma one cell from pollen grain forms pollen tube other cell forms two sperm that travel down tube

Flowering plants go through the process of double fertilization. female gametophyte ovule egg sperm polar nuclei

Flowering plants go through the process of double fertilization. endosperm seed coat embryo one sperm fertilizes the egg other sperm unites with polar nuclei, forming endosperm endosperm provides food supply for embryo

Each ovule becomes a seed. The surrounding ovary grows into a fruit.

Animals, wind, and water can spread seeds. Seeds dispersed by animals can have nutritious fruits or fruits that cling.

Seeds dispersed by wind can have wing- or parachute- like fruits. Seeds dispersed by water can have fruits that float. Cypselae Double samaras

Seeds begin to grow when environmental conditions are favorable. Seed dormancy is a state in which the embryo has stopped growing. Dormancy may end when conditions are favorable. While dormant, embryo can withstand extreme conditions.

Germination begins the growth of an embryo into a seedling. water causes seed to swell and crack coat embryonic root, radicle, is first to emerge water activates enzymes that help send sugars to embryo

Germination begins the growth of an embryo into a seedling. water causes seed to swell and crack coat embryonic root, radicle, is first to emerge water activates enzymes that help send sugars to embryo embryonic shoot, plumule, emerges next leaves emerge last

Once photosynthesis begins, the plant is called a seedling.

Plant hormones regulate plant functions. Hormones are chemical messengers. produced in one part of an organism stimulates or suppresses activity in another part

Gibberellins are plant hormones that produce dramatic increases in size. ending seed dormancy rapid growth of young seedlings rapid growth of some flower stalks

Ethylene causes the ripening of fruits. some fruits picked before they are ripe sprayed with ethylene to ripen when reach destination

Cytokinins stimulate cytokinesis. final stage in cell division produced in growing roots, seeds, and fruits involved in growth of side branches

Auxins lengthen plant cells in the growing tip. stimulates growth of primary stem controls some forms of tropism A tropism is the movement of plant in response to an environmental stimulus.

Went's Experiment Explore the steps involved in an experiment performed by Dutch botanist Frits Went.

Plants can respond to light, touch, gravity, and seasonal changes. Phototropism is the tendency of a plant to grow toward light. auxins build up on shaded side of stem cells on shaded side lengthen causes stem to bend toward light

Thigmotropism is a plant’s response to touchlike stimuli. climbing plants and vines plants that grow in direction of constant wind Thigmotropism A plant turns and bends in response to contact with an object.

Gravitropism is a plant’s response to Earth’s gravitational pull. positive gravitropism is downward growth (roots) negative gravitropism is upward growth (shoots) Gravitropism Plant stems grow upward, against gravity.

Photoperiodism is a response to the changing lengths of day and night. triggers some plants to flower (see below) triggers fall colors/winter dormancy of deciduous trees Photoperiodism A plant moves its leaves during the day.