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

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

3. 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”.
Haploid
Pollen tetrads = microspores

4. Angiosperms: Production of Male Gametophyte
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
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 Developing embryo proper
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 in girth (width), e.g. Tilia stem cross-section

30. • protoderm • ground meristem • procambium 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
Interfascicular cambium
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. Simple versus Compound Leaves
Rachis
Pinnate

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. Guard cells with chloroplasts
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!