Ch. 24- Reproduction of Seed Plants

1. Ch. 24- Reproduction of Seed Plants

2. Haploid Diploid • I. Reproduction With Cones and Flowers • A. Alternation of Generations • - All plants have a life cycle in which a diploid sporophyte generation alternates with a haploid gametophyte generation. MEIOSIS Gametophyte Plant (N) Sporophyte Plant (2N) FERTILIZATION

3. B. Life Cycle of Gymnosperms • - Reproduction in gymnosperms takes place in cones, which are produced by a mature sporophyte plant. • 1. Pollen cones • a. Also called malecones. • b. Produces the male gametophytes, which are called pollengrains.

4. 2. Seed Cones • a. Produce female gametophytes • b. Much larger than pollen cones • c. At the base of each cone scale are found 2 ovules in which the female gametophytes develop

5. 3. Pollination – The pollen is carried by the wind and caught on a sticky secretion (pollination drop) on one of the scales of the female cone.

6. 4. Fertilization • a. When a pollen grain lands near an ovule, it grows a pollentube into the ovule. • b. A sperm from the pollen tube fertilizes the egg in the ovule.

7. Development a. Fertilization produces a zygote which grows into an embryo b. The embryo becomes enclosed in a seed

8. C. Structure of Flowers • - Flowers are the reproductive organs that are composed of four kinds of specialized leaves: sepals, petals, stamens, and carpels. (Figure 24-5)

9. Pistil Stamen Style Stigma Anther Filament Ovary Petal Sepal Ovule

10. 1. Sepals • a. The outermost circle of floral parts contains the sepals, which in many plants are green and closely resemble ordinary leaves • b. Enclose bud and protect the flower during development

11. 2. Petals • a. Brightly colored and found just inside the sepals • b. Attract insects and other pollinators to the flower

12. 3. Stamens • a. Produce male gametophytes – pollen grains • b. Consists of anther and filament

13. 4. Carpels • a. Also called pistils • b. produce female gametophytes – eggs • c. Consists of ovary, style, and stigma

14. D. Life Cycle of Angiosperms • 1. Reproduction in angiosperms takes place within the flower • 2. Following pollination and fertilization, the seeds develop inside protective structures

15. E. Pollination • 1. Most gymnosperms and some angiosperms are wind pollinated, whereas most angiosperms are pollinated by animals. • 2. Insect pollination is more efficient than wind pollination, giving insect-pollinated plants a greater chance of reproductive success.

16. F. Fertilization in Angiosperms • 1. Double Fertilization – Inside the embryo sac, two distinct fertilizations take place • a. First, one of the sperm nuclei fuses with the egg nucleus to produce a diploid zygote, which will grow into the new plant embryo.

17. b. Second, the other sperm nucleus fuses with two polar nuclei in the embryo sac to form a triploid (3N) cell. This will grow into a food-rich tissue know as endosperm, which nourishes the seedling as it grows.

19. II. Seed Development and Germination • - the development of the seed, which provides protection and nutrition for the embryo, was a major factor in the success of plants on land.

20. A. Seed and Fruit Development • 1. As angiosperm seeds mature, the ovary walls thicken to form a fruit that encloses the developing seed. • 2. The term fruit, biologically speaking, applies to any seed that is enclosed within its embryo wall.

22. B. Seed Dispersal • 1. Dispersal by Animals- Seeds dispersed by animals are typically contained in fleshy, nutritious fruits.

23. 2. Dispersal by Wind and Water- Seeds dispersed by wind or water are typically lightweight, allowing them to be carried in the air or to float to the surface of the water.

25. C. Seed Dormancy • 1. Some seeds sprout rapidly while other seeds enter a period of dormancy, during which the embryo is alive but not growing. • 2. Environmental factors such as temperature and moisture can cause a seed to end dormancy and germinate.

26. D. Seed Germination • - The early growth stage of the plant embryo