AP Biology, Chapter 38
Plant Reproduction 

SUMMARY
INTRODUCTION

SEXUAL REPRODUCTION
	Sporophyte and gametophyte generations alternate in the life cycles of plants: a 
	review
		1. Outline the angiosperm life cycle.
			a. Dominant diploid sorophyte
			b. Meiosis yields haploid microspores and megaspores
				i. Microspores  male gametophyte  sperm
				ii. Megaspores  female gametophyte  egg
			c. Sperm + egg  zygote  diploid sporophyte
	Male and female gametophytes develop within a flower's anthers and ovaries, 
	Respectively
		2. List the four floral parts in their order from outside to inside the flower.
			a. Sepals, petals, stamens, carpals
		3. Describe the functions of sepals, petals, stamens, and carpels.
			a. Sepals: green modified leaves surrounding and protecting the petals		
			b. Petals: colored modified leaves in animals-pollinated flowers		
			c. Stamens: male reproductive organs, produce pollen		
			d. Carpels: female reproductive organs, produce ovules
		4. Distinguish between: a) complete and incomplete flowers, b) bisexual and unisexual 
		flowers, and c) monoecious and dioecious plant species.
			a. Complete and incomplete
				i. Complete have sepals, petals, stamens, carpals
				ii. Incomplete don't
			b. Bisexual vs. unisexual
				i. Bisexual = perfect = having stamens and carpals
				ii. Unisexual have either stamens or carpals
			c. Monoecious and dioecious
				i. Monoecious have both male and female on the same plant
				ii. Dioecious have separate male and female plants
		5. Explain by which generation, structure, and process spores are produced.
			a. Both produced on the sporophyte by meiosis
			b. Anthers produce microspores in sporangia or pollen sac
			c. Carpals produce megaspores in the ovule 
		6. Explain by which generation, structures, and processes gametes are produced.
			a. Female
				i. One megaspore divides 3 times by mitosis
				ii.  one egg + 2 polar nuclei + 5 other
			b. Male
				i. Each microspore divides once by mitosis
				ii.  one tube nucleus + one generative nucleus
				iii. Generative nucleus divides again by mitosis giving 2 sperm
	Pollination brings male and female gametophytes together
		7. Explain how pollen can be transferred between flowers.
			a. Grasses and most trees: by wind, large amounts of pollen
			b. Animal-pollinated make less pollen
		8. Describe the sequence of events that lead from pollination to fruit formation.
			a. Pollen on the stigma sends pollen tube down the style
				i. Enters the ovary and grows through the micropyle
				ii. One sperm + egg  zygote
				iii. One sperm + polar nuclei  3n  endosperm
			b. Ovule  seed; ovary wall  fruit
	Researchers are unraveling the molecular mechanisms of self-incompatibility
		9. Describe mechanisms that prevent self-pollination and explain how this contributes to 
		genetic variation.
			a. Some self-pollinate, most avoid it
				i. Separate sexes
				ii. Different maturation times for stamens and carpals
				iii. Physical arrangement of stamens and carpals
				iv. Biochemical self-incompatibility
			b. Cross pollination increases combinations of traits
	Double fertilization gives rise to the zygote and endosperm
		10. Distinguish between pollination and fertilization.
			a. Pollination results in transfer of pollen to the stigma
			b. Fertilization fuses the nuclei of the gametes
		11. Outline the process of double fertilization and describe the function of endosperm.
			a. Process
				i. One sperm + egg  zygote
				ii. One sperm + polar nuclei  3n nucleus
			b. 3n nucleus divides to form a multinucleate cell = endosperm
				i. Nourishes the embryo
				ii. Stores nutrients for the seedling
				iii. In dicots, transfers nutrients to the cotyledons
		12. Explain the adaptive advantage of double fertilization in angiosperms.
			a. No food stored unless fertilization occurs
			b. Saves energy and resources
	The ovule develops into a seed containing and embryo and a supply of nutrients
		13. Describe the development of a plant embryo from the first mitotic division to the 
		embryonic plant with rudimentary organs.
			a. Zygote  terminal cell + basal cell
				i. Terminal cell  proembryo
				ii. Basal cell  suspensor
			b. Proembryo
				i. Forms two lobes in dicots, the cotyledons
				ii. Apical shoot meristem forms between the cotyledons
				iii. Apical root meristem forms where the embryo meets the suspensor	
		14. From a diagram, identify the following structures of a seed and recall a function for 
		each: a) seed coat, b) embryo, c) hypocotyl, d) radicle, e) epicotyl, f) plumule, g) 
		endosperm, h) and cotyledon.
			a. See diagram, 5th edition, page 737
			b. Functions
				i. Seed coat: protects and maintains dormancy
				ii. Embryo: the dormant young sporophyte
				iii. Hypocotyl: embryonic stem below the cotyledon
				iv. Radicle: embryonic root, emerges first during germination
				v. Epicotyl: embryonic stem above the cotyledon
				vi. Plumule: embryonic shoot tip and leaves
				vii. Endosperm: food storage tissue in monocot seeds
				viii. Cotyledon: seed leaves; store food for use by the seedling
		15. Explain how a monocot and dicot seed differ.
			a. Dicot: no endosperm, 2 seed leaves
			b. Monocot: single cotyledon between embryo and endosperm
	The ovary develops into a fruit adapted for seed dispersal
		16. Explain how fruit forms and ripens. List the functions of fruit.
			a. Ovary wall thickens into pericarp
			b. Types
				i. Simple fruits form from one ovary in one flower
				ii. Aggregate fruits form from multiple ovaries in one flower
				iii. Multiple fruits form from many flowers
			c. Ripening
				i. Senescence of pod  opening
				ii. Softening  enzymes digest cell walls
				iii. Acids converted into sugars  sweetening 
		17. Explain how selective breeding by humans has changed fruits.
			a. Increase size
			b. Increase number of flowers on the plant
			c. Increase sugar content
	Evolutionary adaptations of seed germination contribute to seedling survival
		18. Explain how seed dormancy can be advantageous to a plant and describe some 
		conditions for breaking dormancy.
			a. Dormancy ensures germination at advantageous time/place/conditions
			b. Variation in dormancy breaking
				i. Desert: after enough rain
				ii. Crowded undergrowth: after fire
				iii. After extended cold: germination in the spring

ASEXUAL REPRODUCTION
	Many plants can clone themselves by asexual reproduction
		19. Distinguish between sexual reproduction and vegetative reproduction.
			a. Sexual reproduction involves meiosis and fertilization
			b. Vegetative is asexual and gives genetically identical offspring
		20. Describe the natural mechanisms of vegetative reproduction in plants, including 
		fragmentation and apomixis.
			a. Fragmentation
				i. Pieces of leaf, stem, or root may separate and regenerate
				ii. Stolons and adventitious roots may become separated fro the parent
			b. Apomixis
				i. = embryo formation from a diploid parent cell in the ovule
				ii. Seed contains a clone of the parent
				iii. Known to occur in dandlions
	Vegetative propagation of plants is common in agriculture
		21. Describe various methods that horticulturists use to vegetatively propagate plants 
		from cuttings.
			a. Cuttings
				i. Pieces removed, suitably treated, can give an entire plant
				ii. Ex.: potato eyes, African violet leaves, vine sections
				iii. Many cultivars are sterile, anyway
			b. Grafting
				i. Piece of one stem inserted into another
				ii. Nearly all citrus (scion) are grafted onto lemon roots (stock)
			c. Plant tissue culture: excised cells grown in sterile conditions 
		22. Explain how the technique of plant tissue culture can be used to clone and 
		genetically engineer plants.
			a. Entire plants can be grown from single cells
				i. Excised under sterile conditions
				ii. Placed in defined growth medium with hormones
				iii. Cell  undifferentiated callus  organs
			b. Excised cells may be genetically altered before culturing 
		23. Describe the process of protoplast fusion and its potential agricultural impact.
			a. Protoplast = plant cell with cell wall removed using enzymes
			b. Protoplasts from different species can be fused
			c. After tissue culture the fused product has a combination of parent traits
	Sexual and asexual reproduction are complementary in the life histories of many 
	plants: a review
		24. Explain the advantages of using both sexual and asexual reproduction.
			a. Sexual
				i. New combinations of traits for changing environments
				ii. Slower and more complicated
				iii. Young offspring small and vulnerable
			b. Asexual
				i. Fixed combination of traits for constant environment
				ii. Simpler and faster
				iii. Offspring less vulnerable since they are mature parts