Flowers

Flowering Plants Gymnosperms produce seeds on exposed structures called cones. Angiosperms develop unique reproductive organs known as flowers. Flowers are reproductive organs composed of 4 types of specialized leaves: Sepals, Petals, Stamens, & Carpels

Flower Structure Stamen Stigma Carpel Anther Style Filament Ovary Petal Ovule Sepal

Structure & Function 3. The outermost part are the Sepals which open/close to protect the flower. 4. The often brightly colored Petals attract pollinators (animals) to the flower.

Structure & Function 5. Stamen are the male reproductive parts made up of the Anther & Filament. 6. Anthers produce pollen (which contain sperm). 7. Filaments are long thin stalks that support anthers.

Structure & Function 8. Carpels are the female reproductive parts made up of the Stigma, Style, & Ovary. 9. Stigma, produces a sticky substance to trap pollen. It is supported by the Style. 10. The Ovary, contains ovules (eggs).

Stamen Carpel Filament Style Anther Checkpoint Stigma

Pollination

Pollination 11. Most gymnosperms (cone-bearing plants) and some angiosperms are wind pollinators. 12. Releasing pollen into the wind is less efficient, therefore Angiosperms have a variety of adaptations (bright colors and sweet nectar) that attract Animal pollinators. 13. Animals transport pollen directly from flower to flower.

Pollination 14. This is an example of a Mutualistic Symbiotic relationship since the plants benefit from being directly pollinated and the animals benefit because the flower provides a source of food.

Angiosperm Fertilization

Gametophyte Formation In angiosperms, gametophytes develop within the reproductive structures of flowers. Embryo sacs, which are the female gametophytes in angiosperms, form within the ovary of the pistil.

Gametophyte Formation Pollen grains, the male gametophytes, form within the anthers of the stamens.

Fertilization For fertilization to occur in angiosperms, a pollen grain must land on a stigma and then absorb moisture. The pollen grain will then germinate. After fertilization, germination occurs. Germination is when the tube cell forms a pollen tube, and then grows through the stigma and style to the ovary. After the pollen tube penetrates the ovule, two sperm can travel through the pollen tube and reach and fertilize the egg

Fertilization, continued One of the two sperm will fuse with the egg and form a diploid zygote, which will eventually develop into an embryo. The second sperm fuses with the two polar nuclei, producing a triploid (3n) nucleus. This nucleus then develops into tissue called endosperm.

Gametophyte Formation, continued

The endosperm provides nourishment for the embryo The endosperm provides nourishment for the embryo. Endosperm can be used up by the developing embryo or be could still be on the seed after the embryo is fully mature. This process of two cell fusions, which is called double fertilization, is unique to angiosperms.