Lesson Overview Lesson Overview Reproduction in Flowering Plants Lesson Overview 24.1 Reproduction in Flowering Plants

Lesson OverviewLesson Overview Reproduction in Flowering PlantsReproduction in Flowering Plants

Lesson OverviewLesson Overview24.1 Reproduction in 24.1 Reproduction in

Flowering PlantsFlowering Plants


The Structure of Flowers

• Flowers are reproductive organs composed of four different kinds of specialized leaves: sepals, petals, stamens, and carpels.


Sepals and Petals

• Sepals = outermost circle of floral parts o Enclose the bud before it opens and

protect the flower while it is developing

• Petals = brightly colored and found just inside the sepalso Colors, number, and shapes attract

insects and other pollinators


Stamens • Stamens = male parts of the flowero Consists of a stalk called a filament

with an anther at its tipoAnthers = structures that produce pollen

grains—the male gametophytes


Carpels • Carpels = innermost floral parts—produce

and shelter the female gametophytes and, later, seedsoEach carpel has a broad base forming an

ovary, which contains one or more ovules where female gametophytes are produced


Carpels • Pistil = a single carpel or several fused carpels

• Style = diameter of the carpel narrows into a stalk

• Stigma = the top of the style –a sticky or feathery portion specialized to capture pollen


Label the parts of the flower


Label the parts of the flower


The Angiosperm Life Cycle

• Alternation of generations between diploid sporophyte phase and haploid gametophyte stage.


Development of Male Gametophytes

• The male gametophytes—the pollen grains—develop inside anthers.

• First, meiosis produces four haploid spore cells.


Development of Male Gametophytes • Each spore undergoes one mitotic division

to produce the two haploid nuclei of a single pollen grain.

• Two nuclei are surrounded by a thick wall that protects the male gametophyte.


Development of Female Gametophytes • Female gametophytes develop inside each

carpel of a flower.

• The ovules—the future seeds—are enveloped in a protective ovary—the future fruit.


• A single diploid cell goes through meiosis to produce four haploid cells, three of which disintegrate.

Development of Female Gametophytes


Pollination

• Pollination = transfer of pollen to the female portions of the flower

• Some are wind pollinated, but most are by animals


Pollination • Insect pollination is beneficial to insects and

other animals because it provides a dependable source of food—pollen and nectar.

• Plants benefit because the insects take the pollen directly from flower to flower.

• Insect pollination is more efficient than wind pollination, giving insect-pollinated plants a greater chance of reproductive success.


Fertilization

• If a pollen grain lands on the stigma of a flower of the same species, it begins to grow a pollen tube.

• Of the pollen grain’s two cells, one cell—the “generative” cell—divides and forms two sperm cells.

• The other cell becomes the pollen tube.


Fertilization

• The pollen tube contains a tube nucleus and the two sperm cells.

• The pollen tube grows into the style, where it eventually reaches the ovary and enters an ovule.


Vegetative Reproduction

• Vegetative reproduction is the formation of new individuals by mitosis and does not require gametes, flowers, or fertilization

• New plants may grow from roots, leaves, stems, or plantlets

• This takes place naturally in many plants


Examples of Vegetative Reproduction • A potato can grow whole new

plants from buds called “eyes.”• Strawberry plants send out long,

trailing stems called stolons that produce roots, stems, and leaves.

• Many cactus species drop sections of their stems that grow at the base of the larger adults


Vegetative Reproduction

• Can reproduce quickly

• Produces genetically identical offspring, enabling well-adapted individuals to rapidly fill a favorable environment

• Drawback = no new combinations of genetic traits


Plant Propagation (Your plant projects!) • One of the simplest ways to reproduce

plants vegetatively is by cuttings.

• A grower cuts from the plant a length of stem that includes a number of buds containing meristem tissue.

• That stem is then partially buried in soil or in a special mixture of nutrients that encourages root formation.

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Lesson Overview Lesson Overview Reproduction in Flowering Plants Lesson Overview 24.1 Reproduction in Flowering Plants