S tamen = filament + anther

1. Angiosperms: Production of Male Gametophyte Stamen = filament + anther Meiosis inside anther male spores Details follow

2. Haploid Haploid Haploid Haploid Angiosperms: Production of Male Gametophyte Meiosis in lily anther 4 haploid daughter cells, also called “pollen tetrads”

3. Haploid Haploid Haploid Haploid Angiosperms: Production of Male Gametophyte From the point of view of the plant life cycle, anther = male sporangium Each of the 4 pollen tetrads = spore Because of their small size, they are called “microspores”. Pollen tetrads = microspores

4. Angiosperms: Production of Male Gametophyte Haploid Haploid Haploid Haploid As anther matures, 4 microspores of a tetrad separate from each other Haploid nucleus of each microspore undergoes a single mitotic division Mitosis The 2 resulting haploid nuclei become encased in a thick, resistant wall, forming a pollen grain. Pollen Grain

5. Angiosperms: Production of Male Gametophyte Haploid Haploid Haploid Haploid From the point of view of the angiosperm life cycle, a pollen grain is an immature male gametophyte, since it has been produced by the mitotic division of a spore. Mitosis Pollen Grain

6. Angiosperms: Production of Female Gametophyte The pistil (female reproductive portion) is composed of the stigma, style, and ovary.

7. Angiosperms: Production of Female Gametophyte An ovary may contain a number of ovules. Meiosis takes place inside the ovules, resulting in the production of female spores. Details follow

8. Angiosperms: Female Gametophyte Only one of the haploid spores resulting from meiosis in the ovule matures. It undergoes 2 rounds of mitosis to form the “embryo sac”, which has 8 haploid nuclei. Embryo sac = female gametophyte

9. Alternation of Generations: Angiosperms To complete the life cycle, the gametes produced by the male and female gametophyte must unite, restoring the diploid sporophyte. Female gametophyte = embryo sac Immature male gametophyte = pollen grain

10. Fertilization and Embryo Formation Pollen grain landing on stigma of ovary pollen tube growth

11. Fertilization and Embryo Formation 2 haploid cells of pollen grain are called the “generative cell” and the “tube cell” Pollen tube growing from a pollen grain

12. Fertilization and Embryo Formation As pollen tube grows towards ovule, nucleus of “generative cell” divides by mitosis, producing 2 haploid sperm

13. Fertilization and Embryo Formation The pollen grain, along with the pollen tube containing 2 sperm, is the mature male gametophyte.

14. Fertilization and Embryo Formation Pollen tube continues to grow, entering ovule through opening called the “micropyle”

15. Fertilization and Embryo Formation One of the sperm fertilizes the egg, producing a diploid zygote. This zygote will divide and differentiate, forming the sporophyte plant. The angiosperm life cycle has been completed. The other sperm will fuse with the 2 central haploid nuclei in the embryo sac, producing a triploid nucleus. These events are called “double fertilization”.

16. Fertilization and Embryo Formation Tissue that develops from the triploid nucleus = “endosperm”. Energy stored in this tissue nourishes the developing embryo.

18. We have derived many medical compounds from the unique secondary compounds of plants. • More than 25% of prescription drugs are extracted from plants, and many more medicinal compounds were first discovered in plants and then synthesized artificially.

19. Evolutionary Trends in Plant Life Cycles Angiosperms demonstrate an evolutionary trend in which the gametophyte is further reduced in size, and increasingly dependent upon the sporophyte.

20. Development of the Young Dicot Sporophyte Developing zygote, endosperm, and other tissues of the ovule eventually become a seed Bean Corn Example follows

21. Development of the Young Dicot Sporophyte developing ovules Continued Longitudinal section through Capsella ovary

22. Development of the Young Dicot Sporophyte Suspensor Developing embryo proper endosperm Continued

23. Development of the Young Dicot Sporophyte As development continues, cotyledons fill entire embryo sac As the embryo develops, cotyledons begin to grow

24. Development of the Young Dicot Sporophyte Here is a longitudinal section of an ovary with a number of well-developed ovules inside.

25. Development of the Young Dicot Sporophyte Today’s lab: examine external and internal structure of a mature ovule, i.e. a seed:

26. Seed Germination Germination and seedling development in beans

27. Common Plant Cell Types Collenchyma Sclerenchyma Fibers Sclereids Parenchyma

28. Common Plant Cell Types Vessel elements & tracheids: important in xylem tissue cork cells: important in bark tissue sieve tube members & companion cells: important in phloem tissue

29. Primary vs. Secondary Growth Primary growth= growth in length, e.g. in seed germination Secondary growth = growth ingirth(width), e.g.Tilia stem cross-section

30. Primary Meristems Whether they are involved in primary or secondary growth, all plant cells and tissues arise from three primary meristems*: • protoderm •ground meristem •procambium *Meristem: plant tissue that remains embryonic as long as the plant lives, allowing for indeterminate growth

31. Primary & Secondary Growth in a Woody Stem Primary meristems Protoderm Ground meristem Procambium Primary Tissues Epidermis Pith Ground Cortex Primary phloem Primary xylem Lateral Meristem Secondary Tissues Periderm Cork cambium cork 2o phloem 2o xylem Vascular Cambium

32. Tissue Arrangement in Typical Herbaceous Stems Epidermis Cortex Vascular bundle Phloem Xylem Fascicular cambium Interfascicularcambium Pith Monocot Dicot

33. Secondary Growth in a Woody Dicot vascular cambium produces 2o xylem (= wood) to the inside, 2o phloem to the outside

34. Tilia cross-section Primary xylem Vascular cambium Secondary phloem Secondary xylem Phloem ray Pith

35. Cell Types in Secondary Phloem Ray of Bark Sieve tube members Companion cells Fibers

36. Rachis Pinnate Simple versus Compound Leaves

37. Generalized Leaf Anatomy

38. Typical Dicot Leaf X-Section Cuticle Epidermis Palisade Parenchyma Vascular bundles Guard Cells Spongy Parenchyma Stoma

39. Typical Monocot Leaf X-Section Bundle sheath cell Midvein Vein Epidermis Phloem Xylem Stoma Bulliform Cells

40. Leaf Stomata: Allow Gas Exchange Guard cells with chloroplasts Stomata in Zebrina leaf epidermis Stoma Subsidiary cells

41. Bulliform Cells

42. Let’s see some TRICHOMES!