Angiosperms and Seed Plant Reproduction

1. Angiosperms and Seed Plant Reproduction

2. Angiosperms • Angiosperms: seed plants that develop unique reproductive organs known as flowers. • Flowers are an evolutionary advantage because they attract pollinators (birds and bees) • All flowers contain ovaries, which protect the seed and give angiosperms their name • After pollination, ovary develops into fruit which contains the seed • Fruit: wall of tissue surrounding the seed • Fruits are used to disperse seeds (animals eat, digest, deposit seeds in different locations)

3. Diversity of Angiosperms • Extremely diverse- monocots and dicots, woody and herbaceous plants and trees, annual and perennial flowers

4. Seeds contain single cotyledon (one seed leaf in plant embryo) Leaves have parallel veins Flowers have petals and other parts in multiples of three Vascular bundles are scattered throughout the stem Have fibrous roots Seeds contain two cotyledons (two seed leaves in plant embryo) Leaves have branched veins Flowers have petals and other floral parts in multiples of 4 or 5 Vascular bundles arranged in ring in the stem Have taproots Monocots and Dicots Dicots Monocots Monocots and dicots are named for the number of seed leaves in the plant embryo

5. Monocots and Dicots • Monocots include corn, wheat, lilies, orchids and palms • Dicots include roses, clover, tomatoes, oaks, and daisies

6. Monocots

7. Dicots

8. Woody and Herbaceous Plants • Woodiness of stems can also be used to subdivide angiosperms • Woody plants include trees, shrubs, vines • Cells have thick cell walls • Grapes, ivy, blueberries, rhododendrons, roses • Herbaceous plants do not produce wood • Dandelions, zinneas, petunias, sunflowers

9. Woody and Herbaceous Plants

10. Annuals, Biennials, Perennials • Another way to subdivide angiosperms is by the life span of the plant • Three categories of plant life spans • Annuals: grow from seed to maturity and die in one growing season • Marigolds, petunias, pansies, wheat, cucumbers • Biennials: complete their life cycle in two years • Parsley, evening primrose, celery, foxglove • Perennials: live for more than two years • Most have woody stems

11. Annuals and Biennials

12. Gymnosperm Life Cycle • Reproduction in gymnosperms takes place in cones, which are produced by a mature sporophyte plant • Two types of cones: pollen (male) and seed (female) • Pollen cones contain pollen grains • Pollen grains are the entire male gametophyte • Contain haploid nuclei that divide after fertilization • Seed cones are the larger, more familiar cones • Contain ovules at the base of each scale on the cone, in which the female gametophyte develops • Each gametophyte in the ovule contains a few eggs

13. Gymnosperm Life Cycle

14. Gymnosperm Life Cycle • Entire life cycle takes two years to complete before starting over • In spring, pollination begins when male cones release pollen grains in the wind • Caught in sticky secretions from female cones • Fertilization occurs when the pollen grain lands in an ovule, splits open, and grows into a structure called a pollen tube. • Pollen tube will reach the female gametophyte where one sperm will fertilize the egg to create a diploid zygote, which will grow into the new sporophyte plant

15. Gymnosperm Life Cycle

16. Angiosperms- Flower Structure • Flowers are reproductive organs that are composed of four kinds of specialized leaves: sepals, petals, stamens, and carpels • Sepals: outermost part, green and leaflike • Enclose the bud before it opens • Petals: found just inside sepals; attract insects and other pollinators to the flower • How are the bright colors of the flower and evolutionary advantage?

17. Angiosperms- Flower Structure • Within the ring of petals are the structures that produce male and female gametophytes • Male parts • Stamen: made up of anther and filament • Filament: long, thin stalk that supports the anther • Anther: oval sac where male gametophytes are produced by meiosis

18. Angiosperms- Flower Structure • Female parts • Carpels: also known as pistils; produce female gametophytes • Ovary: based of carpel that contains ovules where female gametophytes are produced • Style: narrowing of carpel near top • Stigma: sticky portion of carpel at top of style; attracts pollen grains • Some plants contain flowers that produce both sexes of gametophytes; others produce the sexes on separate flowers

19. Flower Structure

20. Angiosperm Life Cycle • Reproduction in angiosperms takes place in the flower • Following pollination and fertilization, seeds develop in protective structures • Flower production begins life cycle • Male gametophyte develops inside the anther; spore cells undergo meiosis to produce haploid spre cells that become single pollen grains • Female gametophyte develops in the ovules, which are contained in the ovary • Embryo sacis female gametophyte; contains eight nuclei from single divided cells that will become eggs

21. Fertilization in Angiosperms • Pollen lands on stigma; produces pollen tube • Pollen tube reaches embryo sac • Two fertilizations take place- double fertilization • One of the sperm nuclei fuses with the egg to produce a diploid zygote • Other sperm nuclei fuses with two embryo sac nuclei to become triploid (3N) cell, which will grow into the endosperm: food for growing seedling

22. Angiosperm Life Cycle

23. Seed Development and Dispersal • As angiosperm seeds mature, the ovary walls thicken to form a fruit that encloses the developing seed • Dispersal • Animals • Wind and water (wings) • Dormancy due to environmental conditions; germinates when conditions improve

24. Questions • What generation of gymnosperm is the more familiar plant? Is it haploid or diploid? • Sporophyte; haploid • Where are the gametophytes in gymnosperms located? • Male gametophytes (pollen grains) located within the male (pollen) cones. Female gametophytes develop at the base of the scales in the seed cone. • What is the function of the scales on the seed cone? • To produce and protect the seeds. • How is the structure of the pollen grain related to its function? • It has two tiny wings that aid in its dispersal by the wind • Where do the male and female gametophytes develop in angiosperms? • Males in the anther; females in the ovules of the ovary • Explain the process of double fertilization, and why its results are so unusual. • After the zygote has formed, the remaining sperm nuclei fertilize remaining egg nuclei to form triploid endosperm that nourishes the developing embryo