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Trinity Term 1 > Plant development I - plants are composed of repeated structural units > Flashcards

Plant development I - plants are composed of repeated structural units Flashcards

1
Q

plants are composed of…

A

repeated structural units

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2
Q

… coordinate plant development

A

plant hormones

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3
Q

Describe the roots

A
  • highly explorative
  • explore large areas and volumes of soil
  • induce immobility
  • allow social acquisition of nutrients
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4
Q

What are the constraints of immobility

A

exposed to aggregation and inclemency of weather and elements

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5
Q

Describe plant organs

A

can grow above- (shoot system) and under-ground (root system)

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6
Q

List some plant organs

A
  • reproductive shoot (flower)
  • modified leaves (petals)
  • stamens and carpels
  • bud
  • leaf
  • taproot
  • lateral roots
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7
Q

List 3 directions of plant growth

A
  • apical
  • branching
  • radial
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8
Q

Give some examples of apical growth

A
  • shoots
  • taproots
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9
Q

Give some examples of branching growths

A
  • … branches
  • lateral roots
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10
Q

Give some examples of radial growth

A
  • tubers
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11
Q

List three different plant tissue systems

A
  • epidermal system
  • ground tissue system
  • vascular tissue system
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12
Q

Describe permanent plant tissues

A

can be simple, complex or secretory

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13
Q

Describe the simple permanent plant tissues

A
  • parenchyma
  • schlerenchyma
  • collenchyma
  • epidermis
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14
Q

Describe plant organs

A
  • composed of different tissue systems, each characterised by one or more cell types with characteristics that provide specific functions
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15
Q

How can plant tissues be divided?

A

meristems and the permanent tissues

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16
Q

Describe the SAM

A
  • contained in the terminal bud
  • responsible for the production of shoot-organs
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17
Q

SAM

A

shoot apical meristem

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18
Q

Describe the cambia

A
  • vascular cambium and cork cambium
  • meristematic tissues that enable increase in thickness of stems and roots
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19
Q

Describe the RAM

A

produces new cells at the tip of each root

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20
Q

RAM

A

root apical meristem

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21
Q

When does production of new organs occur mostly in plants?

A

post-embryonically

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22
Q

The root and shoot apical meristems are specified … during embryo development.

A
  • early
  • by heart-stage embryo
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23
Q

Meristems regenerate from…

A

differentiated tissues

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24
Q

Describe explants

A
  • when supplemented with adequate amounts and ratios of phytohormones, they produce new shoot and root meristems
  • can generate new plants
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25
Q

phytohormones

A

growth regulators

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26
Q

Describe adventitious roots

A

produced from de novo formed or inactive pre-existing meristems present along the stem

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27
Q

How do plants compensate
for sessility?

A

high regeneration (pretty much any organ can be regenerated)

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28
Q

Describe silent meristems

A
  • can be reactivated by severely damaged plant parts to restore growth
  • such as after wildfires
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29
Q

Why is regeneration essential?

A

grazing activity of herbivores.

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30
Q

How do we visualise plant meristems?

A
  • signalling reporter proteins mark meristematic cells
  • fluorescent markers: GFP, RFP
  • chromogenic markers: GUS
  • luminescent markers (luciferase)
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31
Q

Describe transcriptional reporters

A

reporter protein produced by reporter gene that follows the cell-specific promotor

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32
Q

Describe a post-transcriptional/translational reporter

A

cell-specific protein reporter fusion produced from reporter gene that follows a gene, which itself follows a cell-specific promotor

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33
Q

How a genetic reporters constructed?

A

fusing together promoters and/or coding ones with reporter genes

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34
Q

Describe the Arabidopsis root

A
  • few cell types originate from the meristematic initials
  • organised around a QC
  • three root tip regions: division zone, elongation zone and differentiation zone
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35
Q

QC

A
  • quiescent centre
  • controls meristematic activity
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36
Q

Describe the division zone

A

where new cells are produced

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37
Q

Describe the differentiation zone

A

where adult cells acquire their final specific function

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38
Q

Describe root hair cell specialisation

A
  • distal part of the RAM
  • epidermal cells in contact with two dorsal cortex cells elongate into a root hair with high SA:Vol
  • maximise exchange of water and minerals from the soil
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39
Q

Describe xylem specialisation

A
  • progressive cell wall thickening and disappearance of cytoplasm
  • generates lignified conduits
40
Q

Describe phloem sieve element specialisation

A

loss of citoplasmic components and perforation of transverse cell walls

41
Q

What is the role of the phloem?

A

transport of photosynthates

42
Q

Describe lateral root formation

A
  • cells from the pericycle in proximity of xylem pole cells divide to generate a new LRP
  • self-organises to produce a lateral root
43
Q

pericycle

A

external part of the stele

44
Q

LRP

A

lateral root primordium

45
Q

Describe the function of the cambial meristem

A
  • new (secondary) xyla and phloems are produced here
  • organising core directs the activity of neighbouring meristematic cells
  • organiser cell differentiates into a xylem cell
  • stem cell divides asymmetrically to generate a new organiser cell.
46
Q

Describe the SAM - the specifics

A
  • embedded in layers of leaf primordia that protect it
  • domed shape can be separated into 3 layers of meristematic cells
  • OC and overlying layers visualized using fluorescent reporters (based on marker genes)
47
Q

OC

A

organising centre

48
Q

Describe the activity of the vegetative SAM

A

protrusion produced by the proliferation of the SAM form a phytomer

49
Q

Describe a phytomer

A

consists of a leaf, an axillary meristem and an internode.

50
Q

Describe the production of new leaves

A
  • phyllotaxis
  • plastochron
51
Q

Describe phyllotaxis

A

position of a new leaf along the stem as compared to the previous one

52
Q

Describe plastochron

A

the time interval between the production of two consecutive phyotomers

53
Q

Describe the phyllotaxis of an alternate leaf

A

180 degrees

54
Q

Describe the phyllotaxis of opposite and decussate leaves

A

90 degrees

55
Q

Describe the phyllotaxis of whorls

A

45 degrees

56
Q

Describe the phyllotaxis of spiralled leaves

A

137 degrees

57
Q

Describe the establishment of a new leaf

A
  • all three layers of cells in the SAM contribute to the the tissues
  • L1 generates the epidermis
  • L2 produces the mesophyll parenchyma
  • L3 gives rise to the vasculature
58
Q

vasculature

A

leaf veins

59
Q

Describe the determination of leaf shape

A
  • gradients of growth
  • direction of growth
60
Q

Describe gradients of growth

A
  • generated by cell division (initially) and expansion (subsequently)
  • in most dicots, a mature leaf is composed of a petiole
61
Q

Describe a petiole

A

contains the midvein and a blade (distal and proximal areas).

62
Q

Describe the direction of growth

A

controlled by how cells divide and in which direction they expand

63
Q

Describe the steps of new leaf formation

A
  • founder cell recruitment (lateral and medial growth)
  • distal growth (of primordium)
  • blade initiation
  • intercalary growth (of developing leaf)
64
Q

Describe a mature leaf

A
  • midrib petiole
  • B/P junction
  • proximal to distal
65
Q

Describe a simple leaf

A

single undivided blade

66
Q

Describe a compound leaf

A

subunits are separated by a bladeless region

67
Q

Leaf shape is ultimately defined by …

A

serrations, lobes and leaflets.

68
Q

Within the same species simple genetic alteration can

A
  • severely affect leaf structure
  • e.g. tomato
69
Q

Lobes and leaflets are created by …

A

initiation during
primordium morphogenesis and differentiation

70
Q

initiation

A

persistence of meristematic regions

71
Q

Describe a transverse section of a leaf

A
  • shows asymmetric cell organization
  • adaxial side
  • abaxial side
72
Q

Describe the adaxial side

A
  • upper
  • optimised for light capture and to retain water
73
Q

Describe the abaxial side

A
  • lower
  • suited for gas exchanges
74
Q

Describe the polarity of the leaf blade

A
  • established very early in the primordium
  • defined by the proximity to the SAM (adaxial closer)
75
Q

Mutations in the genes that regulate polarity generate

A

abaxialized or adaxialized leaves

76
Q

In its reproductive phase, the SAM turns into an

77
Q

IM

A
  • inflorescence meristem
  • produces FMs
78
Q

FMs

A
  • floral meristems
  • determinate meristems that produce whorls of new organs
79
Q

Describe the floral organs

A
  • concentric series
  • sepals (form the calyx)
  • petals (form the corolla)
  • stamens
  • carpels
80
Q

sepals and petals together form the

81
Q

What connects the sepal to the bract?

82
Q

Describe the shoot architecture

A
  • based on meristem termination
  • vegetative meristems at terminal and lateral positions can turn into RMs
  • RMs develop into alternative inflorescences depending on whether they terminate with a flower meristem or continue producing new meristems
  • terminal flower meristems give rise to alternative flower architecture depending on the way they branch and produce alternative floral organs
83
Q

RMs

A

reproductive meristems

84
Q

vegetative shoot systems

A

no flowers

85
Q

Raceme

86
Q

Panicle

87
Q

Mutations of homeotic genes alter

A
  • organ identity
  • not their number (except for agamous)
88
Q

What are the main classes of homeotic gene mutations

A

A, B, C and E

89
Q

Ectopic expression of one D class gene is sufficient to

A

confer hybrid identity to petals

90
Q

‘D’ class mutants produce

A

fruits with ovules reminiscent of carpels

91
Q

Plant organs are produced…

A

post-germination from the meristematic tissues

92
Q

The meristems consist of…

A
  • undifferentiated dividing cells
  • non-diving core that coordinates
    their activity
93
Q

Root architecture depends on…

A

the activity of the RAM and the LRPs

94
Q

Shoot architecture is determined by

A

phyllotaxis and branching

95
Q
  • At the reproductive stage of a plant’s lifecycle, the SAM produces flower meristems that terminate into flowers

Trinity Term 1 (38 decks)

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