Chapter 39
Reproduction in plants
aka. How plants have sex
aka. Plant sexy time
- Most flowering plants display sexual reproduction
- Two gametes fuse to produce offspring with a unique combination of genes
- They undergo Alternation of Generations
- Two multicellular life cycle stages
- diploid
- Spore producing sporophyte
- produces spores by meiosis
- a type of cell division that results in four daughter cells each with half the number of chromosomes of the parent cell, as in the production of gametes and plant spores.
- produces spores by meiosis
- Spore producing sporophyte
- haploid
- Gamete producing gametophyte
- produces gametes by mitosis
- a type of cell division that results in two daughter cells each having the same number and kind of chromosomes as the parent nucleus, typical of ordinary tissue growth.
- produces gametes by mitosis
- Gamete producing gametophyte
- Egg is Female
- Sperm is Male
Evolutionary Trends in the Plant Kingdom
- Sporophyte has become larger, more complex
- Flowering plants
- Sporophyte independent
- Dependent gametophyte is only a few cells contained within flowers
- Flowering plants
- Gametophyte has become smaller, less complex
- Moss
- Sporophytes small and dependent on gametohyte (Dominant form)
- Moss
- Female
- 7 cells
- Male
- 2-3 cells
Flower and Sexual Cycle
- Flowers
- ONLY in angiosperms
- All sizes, shapes, colors, and aromas
- Essential process of Sexual reproduction occurs within flowers
- Meiosis/cytokenesis
- reduces chromosome number
- Syngamy (fertilization)
- restores chromosome number
- Meiosis/cytokenesis
"Ideal" Flower
- Uses highly modified leaves arranged in whorls (circular) at the tip of a highly modified stem
- A flower is a highly modified determinate (short term) shoot system
- Pedical, receptical, 4 sets of highly modified leaves are all 2N and part of the sporophyte generation
- Pollen (sperm) and eggs of embryo sac are part of the 1N generation
- Pedical
- flower stalk
- Recepticle
- tip of modified stem with 4 whorls attached
Sexual Cycle