1. Plant Growth & Development: Seed Germination
Plant Science
Plant Growth & Development: Seed Germination
Instructional Materials Service Texas A&M University

2. Bellwork Right page – write down Label top half page
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.

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

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

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

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

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 Right page – write down Date entry 1/25/13 Write “Mnemonic”
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 Right page – date 01/29/13 and write down Date entry 1/29/13
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. 4

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.
3,5

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

51. Plant Emergence (monocot)
In a germinating monocot seed, no hypocotyl arch exists to push the leaf portions through the soil.
Instead, the coleoptile covering the plumule (tight roll of leaves) pierces the soil surface exposing the developing plant to the sunlight.

52. Final Activity Left page Write a summary of today’s discussion.
How would you explain to your friends what you learned? Five or more sentences.
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?

54. Dicot Germination Two types of seed germination occur
among dicots based on how the
seedlings emerge.
Epigeous Germination
Hypogeous Germination

55. Epigeous Germination
In epigeous germination, the hypocotyl of the embryo elongates and raises the plumule, epicotyl, and cotyledons through the soil surface and above the ground.
Garden beans have an epigeous type of germination.

56. Epigeous Germination

57. Hypogeous Germination
In hypogeous germination, the epicotyl elongates and raises the plumule above the ground.
The cotyedons (which are usually still enclosed by the seed coat) and the hypocotyl never emerge and remain below the surface of the soil.
Peas have a hypogeous type of germination.

58. Hypogeous Germination

59. Leaf Formation

60. Dicot Leaf Formation
After emerging through the soil, new leaves form and photosynthesis begins.
In a dicot, the hypocotyl arch straightens, and the plumule is shed.
The cotyledons spread apart to serve as the first leaves to transfer food to other parts of the plant.

61. Dicot Leaf Formation
Once exposed to the air and the light, the epicotyl begins to develop into the stem and true leaves are formed.
The cotyledons shrivel and die as the seedling plant uses their stored food supply.

62. Dicot Leaf Formation
The developing true leaves continue to photosynthesize and produce a constant supply of food reserves.
Hypocotyl elongation is restrained by growth hormones.

63. Monocot Leaf Formation
After the coleoptile and plumule of a monocot emerge, the first true leaves begin to form.
The food supply in the endosperm is used up and photosynthesis begins in the true leaves as they develop.

64. Monocot Leaf Formation
Growth hormones prevent further development of the coleoptile and plumule.
At the time the coleoptile appears above the soil surface, a second root system begins to develop at the base of the coleoptile to form nodal or adventitious roots.

65. Acknowledgements
Shannon Houy, Graduate Technician, Instructional Materials Service, researched and developed the information used in this PowerPoint Presentation.
Christine Stetter, Artist, Instructional Materials Service, developed and illustrated this PowerPoint Presentation.
Keith Zamzow, Curriculum Specialist, Instructional Materials Service, edited and reviewed this PowerPoint Presentation.
Vickie Marriott, Office Software Associate, Instructional Materials Service, edited this PowerPoint Presentation.

66. ALL RIGHTS RESERVED
Reproduction or redistribution of all, or part, of this presentation without written permission is prohibited.
Instructional Materials Service
Texas A&M University
2588 TAMUS
College Station, Texas
 2006