Plant Science

1. Plant Science Plant Growth & Development: Seed Germination Instructional Materials ServiceTexas A&M University - 8385 -

2. Bellwork • Left page • Label top half page • “Brace Map - Seed Parts” • Label bottom half • “Tree Map – Seed Classification” • Right page – write down • Objective: Accurately identify seed parts - Classify types of seeds with examples - Answer: Why do plants use seeds to reproduce.

3. Plant Growth & Development: Seed Germination • Seeds • Seed Classification • Seed Germination • Seed Dormancy • The Germination Process • Leaf Formation

4. Seeds

5. Seeds • The life cycle of many plants begins with a seed. Seeds are essential for the survival and continued existence of many plant species. • Seeds contain the genetic material to produce another plant with identical, similar, or unlike characteristics of the parent plant.

6. Seeds • All seeds contain an embryo and have their own food supply. • The embryo consists of a plumule, epicotyl, cotyledons, hypocotyl, and a radicle.

7. Seeds • The plumule includes the young primordial leaves and growing point of the stem. Plumule

8. Seeds • The epicotyl is the portion of the stem above the cotyledon. Epicotyl Epicotyl

9. Seeds • The cotyledons are the seed leaves used for food storage. Cotyledons Cotyledon

10. Seeds • The hypocotyl is the portion of the stem below the cotyledons. Hypocotyl Hypocotyl

11. Radicle Radicle Seeds • The radicle is the young embryonic root and root tip.

12. Activity – Left Side – Brace Map • 10 minutes • Remember a brace map is used to break down physical things into subparts. • Example: the word “cat” is broken into C A T Use your notes to create a brace map

13. Seed Classification

14. Seed Classification • Flowering plants are classified as monocotyledons (monocots) or dicotyledons (dicots) depending on how many cotyledons they possess, one or two. • A cotyledon is a part of a plant that either stores food or grows to become the first leaves to undergo photosynthesis.

15. Seed Classification • Seeds of dicot plants have two cotyledons. • Seeds of monocot plants have one cotyledon.

16. Dicot Epicotyl Plumule Hypocotyl Radicle Micropyle Hilum Cotyledons Seed Coat

17. Endosperm Cotyledon Coleoptile Epicotyl Axis of Embryo Hypocotyl Radicle Coleorhiza Pedicel Monocot

18. Dicots Dicots include: Garden beans, legumes,alfalfa, soybeans, and cowpeas.

19. Monocots Corn, wheat, rice, and oats are typical monocots.

20. Activity – Left Side – Tree Map • Tree maps are used for classifying things • 10 minutes – break down seeds into the main classifications. Provide three examples of each.

21. Final Activity • Use loose leaf paper and turn in • Write a summary of today’s discussion. • How would you explain to your friends what you learned? • For the final sentence: If you wanted to test your friend’s knowledge of seed parts or classifications, what is one question you would ask?

24. Bellwork • Left page • Date entry 1/25/13 • Write “Mnemonic” • Right page – write down • Objective: Identify key factors needed for germination - - Answer: What is germination

25. Seed Germination

26. Seed Germination Factors affecting seed germination: • Moisture • Temperature • Oxygen • Light

27. Moisture • A seed must have an ample supply of moisture for germination to occur. • Moisture content needed for germination to occur ranges from 25% to 75%. • Once the germination process begins, a dry period or lack of water will cause the death of the developing embryo.

28. Temperature • Temperature affects both the germination percentage and the germination rate. • Germination rate is lower at low temperatures. • Most plant seeds germinate at an optimum temperature range of 68°F to 120°F.

29. Oxygen • Oxygen is necessary for respiration to occur within a seed. Respiration converts the stored food in the seed into energy for germination. • Some seeds require less oxygen than others. • Oxygen deficiency occurs if seeds are planted in flooded or compacted soil.

30. Light • The presence or absence of light may or may not have an effect on germination. • Light is not as important as a viable seed, germination medium, water, optimum temperature, and oxygen.

31. Activity – Left page • Work with your table partner to come up with a mnemonic (sentence) with each word beginning with the following • letters : MTOL letters

32. Seed Dormancy

33. Seed Dormancy • Most seeds produced by mature plants pass through a period of inactivity or dormancy prior to germination. During this period of inactivity, seeds remain viable. • Dormancy may be internal, external, or a combination of both.

34. Embryo (Internal) Dormancy • Dormancy may occur when a mature seed contains an underdeveloped or immature embryo. • Internal dormancy of most seeds involves a period of after-ripening. After-ripening occurs when a seed does not or is not ready to germinate until it completes a certain stage of development. • Some seeds mature in the fruit but do not germinate until released from the fruit.

35. Seedcoat (External) Dormancy • A seed may require a certain amount of light to germinate causing the seed to remain dormant until exposed to light. • The seedcoat may be hard and/or thick, preventing the absorption of water, intake of oxygen, or physically preventing the expansion of the embryo.

36. Adverse Conditions Conditions that may affect the viability and germination of seeds include: • Mechanical Injury • Diseases • Improper Storage • Age • Inadequate Growing Medium

37. Activity • Underneath your mnemonic, in two or three sentences, compare the difference between internal and external dormancy

38. Bell work

39. Bellwork • Left page • Date entry 1/29/13 • Write top half – “Flow map – Water absorption” • Right page – date 01/29/13 and write down • Objective: Identify key steps in germination process. - Answer: What is germination?

40. The Germination Process

41. The Germination Process Steps in the germination process: • Water Absorption • Radicle Emergence • Plant Emergence • Leaf Formation • Photosynthesis

42. Germination

43. Water Absorption • The seed absorbs water and oxygen. • Absorbed oxygen causes the seed to swell and increase in size. • The seed secretes enzymes that convert insoluble starches into soluble sugars. • Soluble sugars dissolve in the absorbed water and are used as food by the plant embryo.

44. Activity • Create a flow map on left page • Show the process of water absorption. • Stay in your seat and work with your table partner.

45. Emergence of Radicle The seed coat ruptures permitting the young root (radicle) to emerge and grow downward to anchor the plant.

46. Emergence of Radicle • In a dicot, the seed coat (testa) splits near the hilum, and the young root becomes the primary root from which all branching roots form.

47. Emergence of Radicle • In a monocot, the young root breaks through the coleorhiza (sheath). • The primary root system that develops from the radicle is temporary and is replaced later with a fibrous root system.

48. Activity • Left page - In three sentences, identify the difference between emergence of a radicle in a monocot versus a dicot.

49. Plant Emergence • The above-soil-surface portion of the plant emerges as the radicle develops into the plant’s root system. • In a dicot, the hypocotyl elongates, forming an arch and pulling the cotyledons upward. • The hypocotyl arch straightens to a vertical position after passing through the soil surface.

50. Plant Emergence