Seeds

1

• Seeds
• Seeds are unique feature of plants

2

• Seeds
• Seeds are unique feature of plants
• Plant dispersal units

3

• Seeds
• Seeds are unique feature of plants
• Plant dispersal units
• Must survive unfavorable
• conditions until they reach
• suitable place (and time) to
• start next generation

4

• Seeds
• Seeds are unique feature of plants
• Plant dispersal units
• Must survive unfavorable conditions until they
  reach
• suitable place (and time) to start next
  generation
• Are dormant

5

• Seeds
• Seeds are unique feature of plants
• Plant dispersal units
• Must survive unfavorable conditions until they
  reach
• suitable place (and time) to start next
  generation
• Are dormant dehydration is key

6

• Seeds
• Seeds are unique feature of plants
• Plant dispersal units
• Must survive unfavorable conditions until they
  reach
• suitable place (and time) to start next
  generation
• Are dormant dehydration is key
• Germinate when conditions are right

7

• Seeds
• Germinate when conditions are right
• Need way to sense conditions while dormant

8

• Seeds
• Germinate when conditions are right
• Need way to sense conditions while dormant
• Need reserves to nourish seedling until it is
  established

9

• Seeds
• (Usually) required for fruit development!

10

• Seeds
• (Usually) required for fruit development!
• Role of fruit is to aid seed dispersal!

11

• Seed Development
• (Usually) required for fruit development!
• Role of fruit is to aid seed dispersal!
• Unfertilized flowers dont develop fruit

12

• Seed Development
• (Usually) required for fruit development!
• Role of fruit is to aid seed dispersal!
• Unfertilized flowers dont develop fruits
• The growth regulators GA, auxin or cytokinin can
  all induce parthenocarpy

13

• Seed Development
• (Usually) required for fruit development!
• Role of fruit is to aid seed dispersal!
• Unfertilized flowers dont develop fruits
• The growth regulators GA, auxin or cytokinin can
  all induce parthenocarpy
• GA auxin or GA cytokinin work best

14

• Seed Development
• (Usually) required for fruit development!
• Role of fruit is to aid seed dispersal!
• Unfertilized flowers dont develop fruits
• The growth regulators GA, auxin or cytokinin can
  all induce parthenocarpy
• GA auxin or GA cytokinin work best
• Hormones from embryo stimulate fruit development

15

• Seed Development
• Hormones from embryo stimulate fruit development
• Other floral organs make inhibitor that blocks
  fruit development until they abscise

16

• Seed Development
• Hormones from embryo stimulate fruit development
• Other floral organs make inhibitor that blocks
  fruit development until they abscise
• Divide seed development into three phases of
  equal time

17

• Seed Development
• Divide seed development into three phases of
  equal time
• Morphogenesis

18

• Seed Development
• Divide seed development into three phases of
  equal time
• Morphogenesis
• Maturation

19

• Seed Development
• Divide seed development into three phases of
  equal time
• Morphogenesis
• Maturation
• Dehydration and dormancy

20

• Seed Development
• End result is seed with embryo packaged inside
  protective coat

21

• Seed Development
• End result is seed with embryo packaged inside
  protective coat
• Seed coat is maternal tissue!

22

• Seed Development
• End result is seed with embryo packaged inside
  protective coat
• Seed coat is maternal tissue!
• Derived from epidermal tissue surrounding ovule

23

• Seed Development
• Seed coat is maternal tissue!
• Derived from epidermal tissue surrounding ovule
• Determines shape of the seed!

24

• Seed Development
• Seed coat is maternal tissue!
• Derived from epidermal tissue surrounding ovule
• Determines shape of the seed!
• Testa mutants have odd-shaped seeds

25

• Seed Development
• Seed coat is maternal tissue!
• Derived from epidermal tissue surrounding ovule
• Determines shape of the seed!
• Testa mutants have odd-shaped seeds
• embryo grows to fill shape set by testa!

26

• Seed Development
• End result is seed with embryo packaged inside
  protective coat
• Endosperm feeds developing embryo (3n grows
  faster)

27

• Seed Development
• End result is seed with embryo packaged inside
  protective coat
• Endosperm feeds developing embryo (3n grows
  faster)
• In many dicots endosperm is absorbed as seed
  develops

28

• Seed Development
• End result is seed with embryo packaged inside
  protective coat
• Endosperm feeds developing embryo (3n grows
  faster)
• In many dicots endosperm is absorbed as seed
  develops
• Often leave a thin layer of endosperm just inside
  testa

29

• Seed Development
• End result is seed with embryo packaged inside
  protective coat
• Endosperm feeds developing embryo (3n grows
  faster)
• In many dicots endosperm is absorbed as seed
  develops
• Often leave a thin layer of endosperm just inside
  testa
• Seeds have three different genetic compositions!

30

• Seed Development
• End result is seed with embryo packaged inside
  protective coat
• Endosperm feeds developing embryo (3n grows
  faster)
• In many dicots endosperm is absorbed as seed
  develops
• In many monocots
• endosperm is seedling food

31

• Seed Development
• Embryogenesis
• Maturation cell division ceases, but cells
  still expand

32

• Seed Development
• Embryogenesis
• Maturation cell division ceases, but cells
  still expand
• Controlled by different genes viviparous mutants
  have normal morphogenesis but dont mature

33

• Seed Development
• Embryogenesis
• Maturation cell division ceases, but cells
  still expand
• Controlled by different genes viviparous mutants
  have normal morphogenesis but dont mature
• Many morphogenesis mutants show normal maturation

34

• Seed Development
• Maturation cell division ceases, but cells
  still expand
• Activate new genes for making storage compounds

35

• Seed Development
• Maturation cell division ceases, but cells
  still expand
• Activate new genes for making storage compounds
• ABA made by maternal tissue initiates this
  process

36

• Seed Development
• Maturation cell division ceases, but cells
  still expand
• Activate new genes for making storage compounds
• ABA made by maternal tissue initiates this
  process
• Seed ABA increases as enter maturation phase

37

• Seed Development
• Maturation cell division ceases, but cells
  still expand
• Activate new genes for making storage compounds
• ABA made by maternal tissue initiates this
  process
• Seed ABA increases as enter maturation phase
• Switch to ABA synthesis by embryo endosperm
  during maturation

38

• Seed Development
• Maturation cell division ceases, but cells
  still expand
• Activate new genes for making storage compounds
• Storage compounds are key for seedlings and crops

39

• Seed Development
• Maturation cell division ceases, but cells
  still expand
• Activate new genes for making storage compounds
• Storage compounds are key for seedlings and crops
• Proteins, lipids carbohydrates but vary widely

40

• Seed Development
• Maturation cell division ceases, but cells
  still expand
• Activate new genes for making storage compounds
• Storage compounds are key for seedlings and crops
• Proteins, lipids carbohydrates but vary widely
• Many 2 metabolites

41

• Seed Development
• Maturation cell division ceases, but cells
  still expand
• Activate new genes for making storage compounds
• Storage compounds are key for seedlings and crops
• Proteins, lipids carbohydrates but vary widely
• Next prepare for desiccation as ABA made by
  embryo (endosperm) increases

42

• Seed Development
• Next prepare for desiccation as ABA made by
  embryo (endosperm) increases
• ABA peaks at mid-maturation, then declines (but
  not to 0)

43

• Seed Development
• Next prepare for desiccation as ABA made by
  embryo (endosperm) increases
• ABA peaks at mid-maturation, then declines (but
  not to 0)
• Blocks vivipary during maturation

44

• Seed Development
• Next prepare for desiccation as ABA made by
  embryo (endosperm) increases
• Make proteins other molecules (eg trehalose)
  that help tolerate desiccation

45

• Seed Development
• Next prepare for desiccation as ABA made by
  embryo (endosperm) increases
• Make proteins other molecules (eg trehalose)
  that help tolerate desiccation
• Next dehydrate (to 5 moisture content) and go
  dormant

46

• Seed Development
• Next dehydrate (to 5 moisture content) and go
  dormant
• Very complex 2 classes of dormancy
• Coat-imposed
• embryo dormancy

47

• Seed Development
• Coat-imposed dormancy (maternal effect)
• Preventing water uptake.

48

• Seed Development
• Coat-imposed dormancy (maternal effect)
• Preventing water uptake.
• Mechanical constraint

49

• Seed Development
• Coat-imposed dormancy (maternal effect)
• Preventing water uptake.
• Mechanical constraint
• Interference with gas exchange.

50

• Seed Development
• Coat-imposed dormancy (maternal effect)
• Preventing water uptake.
• Mechanical constraint
• Interference with gas exchange
• Retaining inhibitors (ABA)

51

• Seed Development
• Coat-imposed dormancy (maternal effect)
• Preventing water uptake.
• Mechanical constraint
• Interference with gas exchange
• Retaining inhibitors (ABA)
• Inhibitor production (ABA)

52

• Seed Development
• Coat-imposed dormancy (maternal effect)
• Preventing water uptake.
• Mechanical constraint
• Interference with gas exchange
• Retaining inhibitors (ABA)
• Inhibitor production (ABA)
• Embryo dormancy (Zygotic effect)

53

• Seed Development
• Coat-imposed dormancy (maternal effect)
• Embryo dormancy (Zygotic effect)
• Making inhibitors (ABA?)

54

• Seed Development
• Coat-imposed dormancy (maternal effect)
• Embryo dormancy (Zygotic effect)
• Making inhibitors (ABA?)
• Absence of activators (GA)

55
Seed Development Coordinated with fruit ripening
fruits job is to protect disperse seed Seeds
remain dormant until sense appropriate
conditions some Lotus germinated after 2000
years!
56

• Seed germination
• Seeds remain dormant until sense appropriate
  conditions
• some Lotus germinated after 2000 years!
• Water

57

• Seed germination
• Seeds remain dormant until sense appropriate
  conditions
• some Lotus germinated after 2000 years!
• Water
• Temperature some seeds require vernalization
  prolonged cold spell

58

• Seed germination
• Seeds remain dormant until sense appropriate
  conditions
• some Lotus germinated after 2000 years!
• Water
• Temperature some seeds require vernalization
  prolonged cold spell
• May break down hydrophobic seed coat

59

• Seed germination
• Seeds remain dormant until sense appropriate
  conditions
• Water
• Temperature some seeds require vernalization
  prolonged cold spell
• May break down hydrophobic seed coat
• May allow inhibitor (eg ABA) to go away

60

• Seed germination
• Seeds remain dormant until sense appropriate
  conditions
• Water
• Temperature some seeds require vernalization
  prolonged cold spell
• May break down hydrophobic seed coat
• May allow inhibitor (eg ABA) to go away
• May allow synthesis of specific RNAs

61

• Seed germination
• Seeds remain dormant until sense appropriate
  conditions
• Water
• Temperature some seeds require vernalization
  prolonged cold spell
• May break down hydrophobic seed coat
• May allow inhibitor (eg ABA) to go away
• May allow synthesis of specific RNAs
• Many require light says photosynthesis is
  possible

62

• Seed germination
• Seeds remain dormant until sense appropriate
  conditions
• Water
• Temperature some seeds require vernalization
  prolonged cold spell
• Many require light says photosynthesis is
  possible
• often small seeds with few reserves

63

• Seed germination
• Seeds remain dormant until sense appropriate
  conditions
• Many require light says that they will soon be
  able to photosynthesize often small seeds with
  few reserves
• Hormones can also trigger (or stop) germination
• ABA blocks it
• GA stimulates it

64

• Seed germination
• Seeds remain dormant until sense appropriate
  conditions
• Many require light says that they will soon be
  able to photosynthesize often small seeds with
  few reserves
• Hormones can also trigger (or stop) germination
• ABA blocks it
• GA stimulates it
• Germination is a two step process
• Imbibition

65

• Seed germination
• Germination is a two step process
• Imbibition is purely physical seed swells as it
  absorbs water until testa pops.
• Even dead seeds do it.

66

• Seed germination
• Germination is a two step process
• Imbibition is purely physical seed swells as it
  absorbs water until testa pops.
• Even dead seeds do it.
• Seeds with endosperm pop testa first, then
  endosperm

67

• Seed germination
• Germination is a two step process
• Imbibition is purely physical seed swells as it
  absorbs water until testa pops.
• Even dead seeds do it.
• Seeds with endosperm pop testa first, then
  endosperm
• Separate processes can pop testa but not
  endosperm

68

• Seed germination
• Germination is a two step process
• Imbibition is purely physical seed swells as it
  absorbs water until testa pops.
• Even dead seeds do it.
• Seeds with endosperm pop testa first, then
  endosperm
• Separate processes can pop testa but not
  endosperm
• Testa and endosperm have different genotypes!

69

• Seed germination
• Germination is a two step process
• Imbibition is purely physical seed swells as it
  absorbs water until testa pops. Even dead seeds
  do it.
• Seeds with endosperm pop testa first, then
  endosperm
• Next embryo must start metabolism and cell
  elongation

70

• Seed germination
• Germination is a two step process
• Imbibition is purely physical seed swells as it
  absorbs water until testa pops. Even dead seeds
  do it.
• Next embryo must start metabolism and cell
  elongation
• This part is sensitive to the environment, esp T
  pO2

71

• Seed germination
• Germination is a two step process
• Next embryo must start metabolism and cell
  elongation
• This part is sensitive to the environment, esp T
  pO2
• Hormones also play a complex role

72

• Seed germination
• Germination is a two step process
• Next embryo must start metabolism and cell
  elongation
• This part is sensitive to the environment, esp T
  pO2
• Hormones also play a complex role
• GA, Ethylene and BR all stimulate

73

• Seed germination
• Germination is a two step process
• Next embryo must start metabolism and cell
  elongation
• This part is sensitive to the environment, esp T
  pO2
• Hormones also play a complex role
• GA, Ethylene and BR all stimulate
• ABA blocks

74

• Seed germination
• Germination is a two step process
• Next embryo must start metabolism and cell
  elongation
• This part is sensitive to the environment, esp T
  pO2
• Once radicle has emerged, vegetative growth
  begins