Sex, Seeds, and Science

1. Sex, Seeds, and Science Meghan Miceli, Gabrielle Quilliam, and Yena Lee

2. Agenda • Introductory Video • Seed structure and function • Seed Development • Anatomy • Reproduction of Plants • Life cycles of gynmosperms and angiosperms • Test Your Knowledge • Closing Song

4. Seed Structure • A seed consists of an embryo plant and a food supply, surrounded by a protective coat • The embryo plant consists of an embryo root (radicle), embryo shoot, and one or two cotyledons • A seed can be either monocotyledonous (one cotyledon) or dicotyledonous (two cotyledons) • The cotyledon refers to the number of organs in the flower; in monocots, there are 3 or 6 whereas dicots have 4 or 5

5. Seed Structure The following table outlines the differences between monocots and dicots:

6. Seed Structure The following diagram of the structure of a bean seed locates the various external and internal structural aspects of a dicot seed.

7. Seed Structure • The cotyledons in many cases provide food for the seed • In other seeds, there is a special food storage tissue called the endosperm • The scientific name for the seed coat is the testa • The microphyle is a small hole through the testa located next to the scar where the seed was attached to the parent plant

8. Seed Structure Overview • Seeds are heterosporous: produce different types of spore • Male and female gametophytes • Male gametophytes produced by microspores, housed in a structure called the microsporangium • Female gametophytes produced by megaspores, housed in the megasporangium

9. Types of Seeds • Gymnosperm: seeds that are not enclosed in ovaries (ie. Pine trees with cones) • Angiosperm: seeds that are enclosed in ovaries (ie. Plum tree with fruit)

10. Female Anatomy • Female gametophytes called eggs • Integument: layer of tissues that protects megasporangium • Ovule: entire structure

11. Female Anatomy

12. Male Anatomy • Male gametophytes-sperm • contained in a pollen grain • travels by wind • Pollen grain becomes pollen tube when germinating

14. Seed Dispersal • seeds often become dormant to adapt to harsh environments • This process involves dehydration of the seed resulting in low metabolism and no growth or development • In favourable conditions, the seed will germinate • Seed dispersal reduces competition between offspring and parent and helps spread the species • The type of seed dispersal lies in the structure of the fruit

15. Germination • The development of the seed into a functional plant • Requires several general conditions • Water: After dormancy, the seeds are dry • Oxygen: For aerobic respiration • Appropriate temperature: For enzyme action • Other specific conditions: • May need exposure to fire or smoke

16. Germination • During germination of a starchy seed, metabolic processes result in the absorption of water • This forms gibberellin in the embryo’s cotyledon • This stimulates the production of amylase, which catalyses the breakdown of starch to maltose • This subsequently diffuses into the embryo for energy release and growth

17. Flower Structure • A flower is a specialized structure designed for sexual reproduction • It reproduces through wind pollination or the transfer of pollen from flower to flower • Animal pollinated flowers are brightly coloured to attract potential pollinators

18. Flower Structure Sepals: protects developing flower while in the bud; usually green Petals: brightly coloured to attract pollinators Stamens: produce microspores that develop into pollen grains containing male gametophytes Filament: stalk of stamen that holds up the anther Anther: terminal sac where pollen is produced Carpels: produce megaspores (female gametophytes) Stigma: tip or carpel; sticky to collect pollen

19. Sex Cells of Plants • All plants show two different generations in their life cycle: • A gametophyte generation, which is haploid, producing spores by mitosis • A sporophyte generation, which is diploid, producing spores by meiosis • Spores = sex cells (undergo meiosis) • These two generations alternate with one another

20. Pollination • The base of a flower contains nectar-secreting glands to attract insects • The anthers produce polled, containing male gametes • The filaments hold the anthers in a position that will likely brush pollen onto visiting insects • If the insect is already carrying pollen from another flower (same species), and brushes it onto the stigma, the flower becomes pollinated

21. Pollination • Self-pollination: pollen from the anther of the same plant falls into its own stigma • Form of in-breeding; less genetic variation • Cross-pollination: pollen is carried from the anther of one plant to the stigma of another plant • increases variation; better fitness in offspring • Female stigma may not receive male pollen due to long distance

22. Fertilization • Happens when the male and female sex cells unite to form a diploid zygote • When the pollen grain adheres to the stigma, it begins to grows a pollen tube down to the ovary • The pollen tube carries male gametes to fertilize the ovary, located in the ovule • The fertilized ovule develops into a seed, and the ovary develops a fruit

23. Making Connections • Pollination: the transfer of pollen to the stigma of a flower • Fertilization: the male and female sex cells unite to form a diploid zygote • Seed Dispersal: the movement of seeds away from the parent • Can travel through the digestive system of animals, by wind, or on the coats of animals, depending on the fruit structure the seed is in

24. Fruits • Fruits are mature ovaries • As seeds develop from the ovules, the walls of the ovary thicken, producing the fleshy part of the fruit • The wall protects the dormant seeds and aids in seed dispersion • Fruits have special “features” (ie. Taste) to help with seed dispersal • Some have propellers to fly with wind or ability to pass through animals digestive systems (animal excretions provide fertilizer)

25. Gymnosperm Life Cycle • The following cycle depicts the life cycle of a gymnosperm. Angiosperms are similar, but rather than cones, there are fruits.

26. Gymnosperm

27. Angiosperm

28. Test Your Knowledge • Draw and label a diagram of a dicotyledonous animal-pollinated flower. (5 marks)

29. Test Your Knowledge • State 3 environmental requirements for germination. • Water: After dormancy, the seeds are dry and need hydration • Oxygen: For aerobic respiration • Appropriate temperature: For enzyme action

30. Test Your Knowledge • Fertilization, pollination and seed dispersal all occur during the reproduction of a flowering plant. In what sequence do these processes occur? • A. seed dispersal pollination fertilization • B. fertilization pollination seed dispersal • C. pollination fertilization seed dispersal • D. seed dispersal fertilization pollination

31. Test Your Knowledge • Describe the metabolic events of germination in a starchy seed. • During germination or a starchy seed, metabolic processes result in the absorption of water. This forms gibberellin in the embryo’s cotyledon, which stimulates the production of amylase. This catalyses the breakdown of starch to maltose, subsequently diffusing into the embryo for energy release and growth.

33. Thank You!!! ;)