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Lesson Overview Reproduction in Flowering Plants Lesson Overview 24.1 Reproduction in Flowering Plants Lesson Overview Reproduction in Flowering Plants The Structure of Flowers • Flowers are reproductive organs composed of four different kinds of specialized leaves: sepals, petals, stamens, and carpels. Lesson Overview Reproduction in Flowering Plants 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 sepals o Colors, number, and shapes attract insects and other pollinators Lesson Overview Reproduction in Flowering Plants Stamens • Stamens = male parts of the flower o Consists of a stalk called a filament with an anther at its tip o Anthers = structures that produce pollen grains—the male gametophytes Lesson Overview Reproduction in Flowering Plants Carpels • Carpels = innermost floral parts—produce and shelter the female gametophytes and, later, seeds oEach carpel has a broad base forming an ovary, which contains one or more ovules where female gametophytes are produced Lesson Overview Reproduction in Flowering Plants 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 Lesson Overview Reproduction in Flowering Plants Label the parts of the flower Lesson Overview Reproduction in Flowering Plants Label the parts of the flower Lesson Overview Reproduction in Flowering Plants The Angiosperm Life Cycle • Alternation of generations between diploid sporophyte phase and haploid gametophyte stage. Lesson Overview Reproduction in Flowering Plants Development of Male Gametophytes • The male gametophytes—the pollen grains—develop inside anthers. • First, meiosis produces four haploid spore cells. Lesson Overview Reproduction in Flowering Plants 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. Lesson Overview Reproduction in Flowering Plants 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. Lesson Overview Reproduction in Flowering Plants Development of Female Gametophytes • A single diploid cell goes through meiosis to produce four haploid cells, three of which disintegrate. Lesson Overview Reproduction in Flowering Plants Pollination • Pollination = transfer of pollen to the female portions of the flower • Some are wind pollinated, but most are by animals Lesson Overview Reproduction in Flowering Plants 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. Lesson Overview Reproduction in Flowering Plants 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. Lesson Overview Reproduction in Flowering Plants 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. Lesson Overview Reproduction in Flowering Plants 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 Lesson Overview Reproduction in Flowering 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 Lesson Overview Reproduction in Flowering Plants 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 Lesson Overview Reproduction in Flowering Plants 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.