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BB10005 > Growth, morphogenesis and cell differentiation > Flashcards

Growth, morphogenesis and cell differentiation Flashcards

1
Q

What is the purpose of secondary growth?

A

It increases the diameter of stems and roots in woody plants.

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2
Q

Where does secondary growth occur?

A

In stems and roots of woody plants but rarely in leaves.

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3
Q

What does the secondary plant body consist of?

A

The tissues produced by the vascular cambium and cork cambium.

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4
Q

In what types of plants does secondary growth occur in?

A

Gymnosperms and many eudicots, but not monocots.

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5
Q

What happens when primary growth from the apical meristems is near completion?

A

The vascular cambium forms.

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6
Q

How does secondary growth occur?

A

Secondary xylem and phloem thicken the stem and vascular rays form. Cells external to the cambium cannot divide so they rupture, including the epidermis. The cork cambium develops from parenchyma cells and produces cork.

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7
Q

What does developmental plasticity describe?

A

The effect of the environment on development.

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8
Q

How do leaves of cabomba adapt to their environment?

A

They are feathery to reduce their resistance to moving water. Surface leaves are pads that aid in flotation. Cells in these leaves are genetically identical. The environment of the apical meristem influences expression of leaf shape genes.

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9
Q

What is morphogenesis?

A

The development of body form and organisation.

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10
Q

What is cell differentiation?

A

The process by which cells with the same genes become different from each other.

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11
Q

What is growth?

A

An irreversible increase in size.

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12
Q

What does cell division in meristems do?

A

It increases cell number and the potential for growth.

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13
Q

What does cell expansion account for?

A

The actual increase in plant size.

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14
Q

How do new cell walls form, in terms of direction?

A

They form in a plane perpendicular to the main axis of cell expansion.

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15
Q

At what point is the plane in which a cell divides determined?

A

During late interphase.

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16
Q

What is a preprophase band?

A

A ring in which microtubules become concentrated.

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17
Q

What is the purpose of the preprophase band?

A

It predicts the future plane of cell division.

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18
Q

What is responsible for leaf growth?

A

A combination of transverse and longitudinal cell divisions.

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19
Q

What determines cell fate?

A

The symmetry of cell division and the distribution of cytoplasm between daughter cells.

20
Q

What else does asymmetrical cell divisions play a role in?

A

Establishing polarity, which is a critical step in plant morphogenesis.

21
Q

What is polarity?

A

The condition of having structural or chemical differences at opposite ends of an organism, such as plants having a root end and a shoot end.

22
Q

What does the first division of a plant zygote determine?

A

It is normally asymmetrical and initiates polarisation into the shoot and root.

23
Q

What mutant arises from a symmetrical first division?

A

The gnom mutant of arabidopsis.

24
Q

How do animal cells grow?

A

Synthesising a protein-rich cytoplasm, which is metabolically expensive.

25
Q

How do plant cells grow faster than animal cells with a lower energy cost?

A

The intake and storage of water in vacuoles.

26
Q

How do plant cells expand primarily?

A

Along the plant’s main axis - the shoot and root.

27
Q

How is the restricted direction of cell elongation caused?

A

The orientation of cellulose mircrofibrils in the cell wall.

28
Q

What is the consequence of cellulose microfibrils not being able to expand?

A

The cell expands perpendicular to their orientation.

29
Q

How do enzymes allow expansion?

A

They weaken cell wall cross-links.

30
Q

What does the cell do to compensate for the expanding cell wall?

A

More miicrofibrils are made to maintain the expanding cell wall.

31
Q

What is pattern formation?

A

The development of specific structures in precise locations.

32
Q

What is the first hypothesis that explains the fate of plant cells?

A

The lineage based one: in which cell fate is determined early in development and passed on to progeny cells.

33
Q

What is the secondary hypothesis that explains the fate of plant cells?

A

The position based hypothesis: cell fate is determined by final position in an emerging organ.

34
Q

What did laser ablation experiments show?

A

It suggested that the plant cell fate is established late in development and depends on signaling from neighbouring cells.

35
Q

What is cell fate in animals dependent on?

A

Lineage-dependent.

36
Q

What are phase changes?

A

Developmental phases - developing from a juvenile phase to an adult vegetative phase to an adult reproductive stage.

37
Q

Where do phase changes occur within the plant?

A

The shoot apical meristem.

38
Q

What is the most obvious morphological changes that occur in phase changes?

A

Leaf size and shape.

39
Q

What does flower formation involve?

A

A phase change from vegetative growth to reproductive growth.

40
Q

What triggers flower formation?

A

A combination of environmental cues and internal signals (day length and hormones).

41
Q

What is the transition from vegetative growth to flowering associated with?

A

The switching on of floral meristem identity genes.

42
Q

Is floral growth determinate?

A

Yes.

43
Q

What are flowers primordiums?

A

Sepal, petal, stamen and carpel.

44
Q

What are the identity genes that plant biologists have identified?

A

MADS-box genes.

45
Q

What can a mutation in plant organ identity genes cause?

A

Abnormal floral development.

46
Q

What does the ABC hypothesis say?

A

It identifies how floral organ identity genes direct the formation of the four types of floral organs.

BB10005 (22 decks)

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