Understanding Angiosperm Reproduction Process

1. Chapter 38 Reading Quiz • By what process do sporophytes make spores? • What are the two sterile parts of a flower? • What is the name of the food-storing tissue of a seed? • Name one condition that could break “seed dormancy”. • In plants, what is asexual reproduction also known as?

2. 1. Outline the angiosperm life cycle. • Has alternation of generations • Sporophyte is everything from zygote to mature plant • Gametophyte is just pollen (sperm) & embryo sac (egg) 

4. 2. List the four floral parts in their order from outside to inside of the flower. • Sepals  green petal-like structures • Petals  colored structures • Stamens  male structures • Carpels  female structures 

5. 3. Distinguish between complete and incomplete flowers. • Complete flowers  those that have all four plant organs • Incomplete flowers  those lacking one or more of the four organs ex: grasses are incomplete (lack petals) 

6. 4. Distinguish between a perfect and imperfect flower. • Perfect flower  those equipped with both stamens and carpels (can still lack sepals or petals) • Imperfect flower  have only stamens or carpels (are always incomplete) 

7. 5. Distinguish between monoecious and dioecious. • Monoecious  if staminate & carpellate flowers are located on the same individual plant ex: corn • Dioecious  when staminate & carpellate flowers are on separate plants ex: date palms 

8. 6. Explain by which generation, structure, and process spores are produced. • Generation  sporophyte • Structure  within flower structure • Process  meiosis 

9. 7. Explain by which generation, structure and process gametes are produced. • Generation  gametophyte • Structure  within pollen & embryo sac structures • Process  mitosis 

10. 8. Describe the development of a pollen grain in angiosperms. • Within the pollen sacs of the anther, the diploid cells undergo meiosis • This forms 4 haploid microspores • Each one divides once by mitosis and produces 2 cells (generative & tube) • These 2 cells together constitute a pollen grain (an immature male gametophyte) 

12. 9. Of the pollen grain, distinguish among generative cell, tube cell, and sperm nucleus. • Generative cell  the half of the pollen grain that will form 2 sperm • Tube cell  when the pollen lands on the stigma of the carpel, the pollen tube begins to grow through to deliver the sperm to the egg • Sperm nucleus  the 2 sperm created by the generative cell 

13. 10. Describe the development of the embryo sac, and explain what happens to each of its cells. • Embryo sac: 1. Antipodal cells (3) 2. Polar nuclei (2) 3. Egg (1)  female gamete 4. Synergids (2)  flank egg cell 

14. 11. Describe how pollen can be transferred between flowers. • Pollen can be transferred by: 1. Wind 2. Insects 3. Birds 

15. 12. Describe mechanisms that prevent self-pollination, and explain how this contributes to genetic variation. • Similar to immune response in animals • “S-genes” recognize self - if pollen & stigma have same alleles at S-locus, then pollen will not grow tube • The incompatibility can happen at different locations - block inside pollen itself - response by carpel’s stigma 

17. 13. Outline double fertilization and describe function of endosperm. • the pollen tube grows down the style toward the ovary • The generative cell divides by mitosis and forms two sperm • A chemical attractant draws the sperm to the ovary & discharges the two sperm • One sperm fertilizes the egg to form the zygote • The other combines with the 2 polar nuclei to form a triploid nucleus • This gives rise to the endosperm, which stores food 

19. 14. Describe the development of a plant embryo from the first mitotic division to an embryonic plant with rudimentary organs. • Endosperm development  rich in nutrients • Embryo development  first division is transverse, splitting into basal & terminal cells • Terminal gives rise to most of the embryo • Basal becomes thread of cells to anchor the embryo & transfer nutrients • Rudimentary cotyledons appear, and the embryo elongates, stem & root meristems begin to grow out 

21. 15. Draw a seed diagram and label and explain the following structures:a. seed coat b. embryo c. endosperm d. cotyledons

22. 16. Explain how a monocot and dicot seed differs. • Monocot  one cotyledon (seed leaf) for embryo nutrition • Dicot  two cotyledons for embryo nutrition 

23. 17. Describe several functions of fruit and explain how fruits form. Functions  • Enclose & protect seeds • Aid in dispersal by wind or animals Formation  • Begins to develop after pollination triggers hormonal changes that cause the ovary to grow • Pericarp is the thickened wall of the ovary (fruit) 

24. 18. Distinguish among simple, aggregate, and multiple fruits and give examples of each. Simple  a fruit derived from a single ovary • May be fleshy (cherry) or dry (soybean) Aggregate  results from a single flower that has several carpels • Blackberry, raspberry Multiple  develops from an inflorescence (a group of flowers tightly clustered together) • Pineapple 

25. 19. Explain how seed dormancy can be advantageous to a plant and describe some conditions for breaking dormancy. • Seed dormancy  very low metabolic rate & no growth or development • Increases chance that seed will germinate at a time that is advantageous Conditions  environmental • Substantial rainfall • Intense fire • Extended exposure to cold • Passage through an animal’s digestive tract 

26. 20. Explain how a seed mobilizes its food reserves and describe the function of aleurone,  -amylase, and gibberellic acid. • Once seed imbibes water, this triggers the seed to break it’s coat and begin digesting the food supply • This happens because hormones called gibberellins (GA) signals the aleurone (thin outer layer of endosperm • The aleurone synthesizes & secretes the digestive enzymes that hydrolyze the food • The  - amylase is the enzyme that hydrolyzes the food supply to make it available to the now developing seed 

28. 21. Describe variations in the process of germination including the fate of the radicle, shoot tip, hypocotyl, epicotyl, and cotyledons. • Radicle  the root of the embryo, emerges from the seed first • Shoot tip  breaks the soil surface • Hypocotyl  straightening of this pulls the shoot & cotyledons from the soil • Epicotyl  elongation and “unhooking” of this pulls new shoot & leaves to the surface • Cotyledons  some rise with the shoot (bean), some stay underground (pea) 

30. 22. Distinguish between sexual reproduction and vegetative reproduction. • Sexual  involves two different individual plants (one male, one female) - result in genetic variation • Vegetative  essentially a clone of a plant, reproduced through asexual means - possible due to indeterminate growth 

31. 23. Describe natural mechanisms of vegetative reproduction in plants including fragmentation and apomixes. • Fragmentation  the separation of a parent plant into parts that re-form whole plants (one of the most common types) • Apomixes  in dandelions and others - produce seeds without their flowers being fertilized - a diploid cell in the ovule gives rise to the embryo, and the ovules mature into seeds, which are dispersed 

32. 24. Describe various methods horticulturists use to vegetatively propagate plants from cuttings. • Methods are based on the ability of plants to form adventitious roots or shoots • Most houseplants & orchard trees are produced by cuttings • At the cut end of a stem or shoot, a mass of dividing, undifferentiated cells called a callus forms, and the roots develop from this • Grafting  a cutting can be grafted onto another of a closely related species 

33. 25. Explain how the technique of plant tissue culture can be used to clone and genetically engineer plants. • It is possible to grow whole plants by culturing even single parenchyma cells in an artificial medium with nutrients & hormones • Can introduce foreign genes by firing DNA coated pellets into the cells 

34. 26. Describe the process of protoplast fusion and its potential agricultural impact. • Protoplast fusion  - being coupled with tissue culture methods - protoplasts are plant cells that have had their cell walls removed - can be screened for mutations & improve the agricultural value of the plant - could fuse two protoplasts that otherwise would be incompatible & produce a hybrid 

35. Protoplasts

36. 27. Define monoculture and list its benefits and risks. • Monoculture  the cultivation of large areas of land with a single plant variety • Has helped farmers feed populations • Fragile ecosystems; where there is little genetic variability, there is little adaptability 

37. 28. Define growth, morphogenesis, and cellular differentiation. • Development  the sum of all of the changes that progressively elaborate an organism’s body • Growth  an irreversible increase in size, results from cell division and cell enlargement • Morphogenesis  accompanies growth; it is the development of form • Cellular differentiation  the acquisition of a cell’s specific structural and functional features 

38. 29. Describe how the plane of cell division is determined. • The plane in which a cell will divide is determined during the late interphase • The microtubules of the cytoskeleton rearrange • The band that they form will be where the cell will divide 

39. 30. How is cellular differentiation controlled? • Cellular differentiation is controlled by the genes • Differentiation continues throughout the plant’s life • Meristems sustain this indeterminate growth • Differentiation reflects the synthesis of different proteins in different types of cells 

40. 31. Describe what pattern formation and positional information is. • Pattern formation  the development of specific structures in specific locations - a key element in the overall development of an organism’s form • Positional formation  what pattern formation depends upon - signals of some kind that indicate each cell’s location within an embryonic structure, such as a root tip 

41. 32. Describe pattern formation in flower development. • The transition of a vegetative shoot tip into a floral meristem • Begins with a combination of environmental clues (daylength, hormones) • The “meristem identity genes” are switched on • The protein products of these genes are transcription factors that help to activate the genes required for development of the floral meristem • Once induced to flower, positional info commits each part to become one plant organ 