Plant Reproduction and Hormones INCLUDES: Ch 39- 1st reading assignment Ch 38- 2nd reading assignment Note: This is the

1. Plant Reproduction and Hormones INCLUDES: Ch 39- 1st reading assignmentCh 38- 2nd reading assignment)*Note: This is the second and last PowerPoint for the plant unit.

2. Plant Hormones (Ch 39) The Big 5 to Know (also on plant packet): -Auxin -Cytokinins -Gibberellins -Abscisic Acid -Ethylene

3. Auxin Auxin= hormone that promotes elongation of young developing shoots. -Where would this be naturally produced in plant? -adding can produce formation of roots, fruit growth -Ironically, a very excessive concentration of auxin will INHIBIT growth http://bcs.whfreeman.com/thelifewire/content/chp38/3802003.html

5. Cytokinins Cytokinins=modified forms of adenine that stimulate cytokinesis -involved in: cell division and differentiation apical dominance retard aging -What is a benefit of adding cytokinins to a plant (hint: florists benefit from this)?

7. Gibberellins Gibberellins: -stimulate growth in leaves + stems, but not much effect on roots -commercial applications involve spraying some fruits with this hormone in order to cause to grow larger and farther apart -found in seeds, and with good environmental conditions, cause seeds to break dormancy

9. Abscisic Acid (ABA) Abscisic Acid= produced in terminal bud and helps prepare plants for winter Acts as stress hormone, closing stomata in times of water-stress thus reducing transpiration water loss Thus which hormone does ABA seem to counter?

10. Ethylene Gas hormone that diffuses thru air spaces between plant hormone Causes senescence (aging) in plants�fruit ripening and leaf abscission Ethylene inhibits auxin production (why?) If auxin is very excessively high, you learned this can inhibit growth. Would this stimulate or inhibit ethylene?

11. Other Words� Tropism- growth responses that result in curvature of plant organs toward/away from stimuli PHOTOtropism-response to light (this is due to auxin transport to shoot tips where light is present) GRAVItropism- response to gravity (need not know mechanism, but can read about it if interested!)

12. Circadian rhythm= �biological clock� -plants display �sleep movements� in opening/closing stomata even if kept in total darkness In other organisms: -fungi produce spores only during certain hours -human features (blood pressure, temp, metabolic rate) fluctuate with time of day

13. Plants Respond to Stress Water Deficit= Deal with by wilting (the shape of the wilting leaves reduces exposure to sun), closing stomata, inhibiting further growth Oxygen Deprivation (water logged soil means no cell respiration in roots)= plants can form air tubes that extend from submerged roots to surface so oxygen can reach roots Heat Stress= Transpiration will help evaporative cooling Salt Stress= Excessive salts lower water potential in soil causing water deficit�plants can make their own �compatible solute� that will lower their cells� water potential thus allowing water to enter

14. Plant Reproduction (Ch 38)Early Plants Early plants were still dependent on water to complete their life cycle. But before long, the demands of life on land favored evolution of plants that were resistant to drying rays of the sun and were more capable of conserving water.

15. Seeds The ability to form seeds is a trait that now is the most dominant group of photosynthetic organisms on land. A seed is an embryo of a plant encased in a protective seed coat. The embryo is the early development stage.

16. Seed Plants Seed plants are divided into two groups: gymnosperms which bear their seeds on the surface of cones and angiosperms which are also called flowering plants that have seeds within a layer of tissue that protects the seed.

17. Angiosperms have unique reproductive organs known as flowers. Flowers contain ovaries, which surround and protect the seeds.

18. The unique angiosperm fruit (thick wall of tissue surrounding the seed) is another reason for the success of these plants. They attract animals and when the animal eats the fruit, seeds from the core generally enter the animal�s digestive system. The seeds leave the digestive tract ready to sprout and can be spread many miles.

19. Life Cycle Some angiosperms have a life cycle that is one year long. These are called annuals. Some angiosperms complete their life cycle in two years. These are called biannuals. Some angiosperms live for more than two years. These are called perennials.

20. Alternation of Generations All plants have a life cycle in which a diploid sporophyte generation alternates with a haploid gametophyte generation.

21. Flowers are reproductive organs They have four specialized structures: Sepals Petals Stamen Carpel

22. Sepals The outermost circle of floral parts

23. Petals Brightly colored to attract pollinators and found inside the sepals

24. Stamen Male parts that include the anther (oval sac where meiosis takes place) and filament (long stalk that supports the anther). The anthers are covered with a yellow dust called pollen.

25. Carpel Female parts that include the ovary (which produces female gametophytes) and the stigma (sticky portion where pollen grains land). The stigma is supported by a stalk called the style.

26. Fertilization Fertilization in plants happens when a pollen grain is released from the anther and deposited on the stigma.

27. Flowering plants (angiosperms) often rely on animals and insects to carry pollen from one plant to another. It is beneficial to animals because plants can produce nectar (a sugar rich liquid) that animals can eat. It is beneficial to plants because pollen is taken directly from flower to flower. This is a mutual symbiotic relationship.

28. Steps in Fertilization 1. When the pollen grain lands on the stigma, it grows a pollen tube. The pollen tube grows into the style and enters the ovule. 2. The nucleus in the pollen grain divides and forms two sperm nuclei. 3. One sperm fuses with the egg to make a diploid zygote. This will become the plant embryo. The other sperm nuclei fuses with two polar nuclei (remember how making an egg is uneven cytokinesis and results in polar bodies?)�and makes a TRIPLOID 3N cell. This becomes the endosperm which will be the food supply for the seed. *Animation on NEXT SLIDE*

29. Fertilization Animation http://www.emunix.emich.edu/~ghannan/systbot/doublefertanimation.html Because the endosperm and zygote are fertilized, this is called double fertilization.

31. Fertilization and Life Cycle

32. Flower to Fruit! As angiosperm seeds mature, the ovary walls thicken to form a fruit that encloses the developing seeds. Remember the term �fruit� applies to any seed that is enclosed within its embryo wall. Therefore �fruit� also includes beans, peas, and tomatoes.

35. Know the plant reproduction Vocab on sheet (not all included here)

36. Parts to a Seed

37. Questions to think about: 1. What are the adaptations seed plants have over seedless plants? 2. What are some different ways seeds have adapted to spreading? 3. Why is seed dormancy important and what kind of conditions are needed for breaking dormancy (how does it vary?) 4. What is the function of the cotyledon and endosperm for the seed?