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Cell Biology > Plant structure & growth 2 > Flashcards

Plant structure & growth 2 Flashcards

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1
Q

What is the general role of meristems?

A

Generating cells for primary + secondary growth

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2
Q

What type of tissue are meristems?

What are the 2 types of meristems?

A

Embryonic tissue

Apical & lateral

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3
Q

What does secondary growth cause?

A

Increase in diameter of stems + roots in woody plants

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4
Q

Where in a woody plant does secondary growth occur?

A

Stems & roots

- rarely leaves

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5
Q

What does the secondary plant body consist of?

A

The tissues produced by the vascular cambium + cork cambium

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6
Q

What type of plant is secondary growth a characteristic of?

A

Gymnosperms & many eudicots

- NOT monocots

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7
Q

What happens when primary growth from apical meristems nears completion?

A

Vascular cambium forms

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8
Q

What happens during 1st year of secondary growth in the vascular cambium?

A

> Secondary xylem & phloem thicken the stem
Vascular rays form
Cork cambium develops from parenchyma cells + produces cork

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9
Q

What happens to cells external to the cambium during secondary growth?

A

Cells (including epidermis) cannot divide so rupture

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10
Q

What are vascular rays?

A

Radial files of parenchyma

- connects secondary xylem + phloem for nutrient + water movement and repair

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11
Q

What happens in the 2nd year of secondary growth?

A

Secondary growth in secondary xylem, phloem & cork

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12
Q

What is bark?

A

All tissue exterior to vascular cambium

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13
Q

What does developmental plasticity describe?

Give an example

A

The effect of environment on development

Cabomba caroliniana forms diff leaves depending on whether or not apical meristem is submerged

  • feathery leaves underwater reduces resistance to moving water
  • pads on surface to aid flotation
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14
Q

What does development consist of?

Define the components

A

> Growth = irreversible increase in size
Morphogenesis = development of body form & organisation
Cell differentiation = process by which cells w/ same genes become diff from each other

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15
Q

What are the 2 components of growth?

A

Cell division

Cell expansion

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16
Q

What does cell division in meristems do?

What is cell expansion accountable for

A

Increases cell no. + the potential for growth

Actual increase in plant size

17
Q

In what plane do new cell walls form?

A

Perpendicular to main axis of cell expansion

18
Q

When is the plane in which a cell divides determined?

How is it predicted?

A

During late interphase

Microtubules become concentrated into a ring (=preprophase band) that predicts the future of cell division

19
Q

Leaf growth results fro m a combination of what?

A

Transverse + longitudinal cell divisions

20
Q

It has long been thought that leaf form is determined by what?

A

Plane of cell division

21
Q

What does a mutation in the tangled-1 gene in maize do?

A

Affects longitudinal divisions BUT doesn’t affect leaf shape

Mutant leaves grow slower

22
Q

What determines cell fate?

A

The symmetry of cell division

= distribution of cytoplasm between daughter cells

23
Q

Give an example of asymmetrical cell division

A

Asymmetrical cell division and change in plane of cell division in the formation of guard cells

24
Q

What do asymmetrical cell division play a role in?

A

Establishing polarity

- critical step in plant morphogenesis

25
Q

What is polarity?

A

The condition of having structural or chemical differences at opposite ends of an org
e.g. plants have roots + shoots

26
Q

Describe the 1st division of a plant zygote

A

> Asymmetrical

>Initiates polarisation into root + shoot

27
Q

How are gnom mutants of Aridopsis different to normal plants?

A

> Result from a symmetrical 1st division
Have no leaves or roots
Defect traced to an inability to transport auxin in a polar manner

28
Q

How is the expansion of plant cells different to animal cells?

A

Animals: synthesise protein-rich cytoplasm (metabolically expensive)

Plants: grow rapidly at lower energy cost by storage of water in vacuoles
- only 10% is by synthesis of cytoplasm

29
Q

In what plane do plant cells expand primarily?

A

Along plant’s main axis

- shoot + root

30
Q

What does the orientation of cellulose microfibrils in the cell wall cause?
How?

A

Restricts direction of cell elongation

  • microfibrils don’t stretch so cell expands perpendicular to their orientation
  • enzymes weaken cross-links allowing more expansion
31
Q

What is pattern formation?

A

Development of specific structures in precise locations

32
Q

What are the 2 hypotheses to explain the fate of plant cells?

A

Lineage-based
= cell fate is determined early in development + is passed on to progeny cells

Position-based
= cell fate is determined by final position in an emerging organ

33
Q

What do laser ablation experiments suggest about plant cell fate?

How does this compare to animal cells?

A

Cell fate is established late in development + depends on signalling from neighbouring cells

Cells are largely lineage-dependent

34
Q

Describe how positional info is conveyed by cell-to-cell communication in Arabidopsis root epidermis.
What does this result in?

A

Epidermal cell boarding single cortical cell expresses GLABRA-2
= hairless

Epidermal cell boarding 2 cortical cells doesn’t express GLABRA-2
= develops a root hair

35
Q

What does flower formation involve?

A

A phase change from vegetative growth to reproductive growth

  • associated w/ switching on of floral meristem identity genes
36
Q

What is flower formation triggered by?

A

Combination of enviro cues (e.g. day length) + internal signals (e.g. hormones)

37
Q

What are the organ identity gens that regulate the development of floral pattern known as?

A

MADS-box genes

38
Q

Which organ develops where only A genes are expressed?

What about A + B genes?

What about B + C genes?

What about only C genes?

A

Sepals

Petals

Stamens

Carpels

Cell Biology (23 decks)

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