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Life of Earth 2 > Plant growth > Flashcards

Plant growth Flashcards

1
Q

Generally describe how plants grow

A

Irreversible quantitative change in cell size + no.

Not all cells contribute to growth

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2
Q

Where is growth localised to in plants?

A

Embryonic regions = meristems

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3
Q

How is growth in plants different to growth in animals?

A

Plants:
> growth is restricted to certain regions
> growth is accompanied by increase in no. of parts
> constantly need to replace organs

Animals:
> body plan + organs are laid down in embryogenesis

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4
Q

Which organs only have determinate growth?

When do they cease to grow?

A

Flowers
Fruit
Leaves

Maturity

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5
Q

What is phyllotaxy and what causes it?

Where do floral primordial form?

A

Arrangement on leaves on a stem
- opposite or spiral arrangement

Caused by regular changes in distribution of auxin in meristem

Regions of high auxin conc

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6
Q

What do meristems give rise to?

A

Initials (=stem cells) which remain in meristem

Derivatives which become specialised in mature tissue

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7
Q

Where are apical meristems located?

A

Tips of roots and shoots + in axillary buds of shoots

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8
Q

What is primary growth?

A

Apical meristems elongating shoots + roots

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9
Q

What are the types of primary meristem that apical meristems may differentiate into?

A

Protoderm
Procambium
Ground meristem

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10
Q

Where is protoderm located and what does it develop into?

A

Around outside of stem

Develops into epidermis

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11
Q

Where is procambium located and what does it develop into?

What does it produce?

A

Inside of the protoderm

Develops into primary xylem + phloem

Produces vascular cambium (secondary meristem)

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12
Q

Where the ground meristem located and what does it develop into?

What does it produce?

A

Inside the protoderm and surrounds the procambium

Develops into cortex + pith

Produces cork cambium (secondary meristem)

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13
Q

What is secondary growth?

A

When lateral meristems add thickness to woody plants

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14
Q

What are the 2 secondary lateral meristems?

A

Vascular cambium

Cork cambium

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15
Q

What does the vascular cambium do?

A

Adds layers of vascular tissue = secondary xylem (wood) + secondary phloem

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16
Q

What does the cork cambium do?

A

Replaces the epidermis with periderm

= thicker + tougher

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17
Q

What are the 3 categories of plants based on their life-cycle length?

A

Annuals = life completed in 1yr or less

Biennials = 2 growing seasons

Perennials = long lived

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18
Q

What is the root tip covered by and what is its purpose?

A

Root cap

= protects apical meristem as root pushes through soil + secretes a polysaccharide slime that lubricates soil

19
Q

What are the 3 overlapping zones fo growth behind the root tip?

A

Zone of:
> cell division
> elongation
> differentiation/maturation

20
Q

Where do lateral roots arise from?

A

The pericycle

21
Q

What is the pericycle?

A

Cylinder of parenchyma or sclerenchyma cells that lies inside the endodermis

22
Q

What is a SAM?

A

Shoot apical meristem

= dome-shaped mass of dividing cells at shoot tip

23
Q

Where do axillary buds develop from?

A

Meristematic cells left at the bases of leaf primordia

24
Q

Where do leaves develop from?

A

Leaf primordia along the sides of the apical meristem

25
Q

How does auxin affect axillary buds?

A

Represses development of axillary buds into shoots

= acts as an inhibitor

26
Q

What is apical dominance?

A

Where the central stem is dominant over smaller side stems

27
Q

What does apical dominance help to do?

A

Maintain dormancy of most non-apical buds

- dormancy depends on proximity to active apical bud

28
Q

What does pruning plants do?

A

Removes the dominance of the active apical bud

- auxin is produced at apex which inhibits growth of lateral buds further down stem

29
Q

What are intercalary meristems?

A

Only in monocotyledons

At base of internodes + leaf blades
-> growth occurs at base of stems + leaves
= allows for rapid growth after defoliation by herbivores

30
Q

Which types of plants have secondary growth?

A

(Woody plants)

Gymnosperms
Eudicots

NOT monocots

31
Q

How many times has secondary growth evolved?

A

3 in 420my of vascular plant existence

32
Q

Which group has lost secondary growth?

A

Monocots

type of angiosperm

33
Q

What is the purpose of secondary growth via the vascular cambium?

A

Adds structural support + increases vascular flow

34
Q

What does the cork cambium produce?

What is the purpose of this?

A

A tough, thick covering of wax-impregnated cells

Protects stem from:
water loss
fire
insect attack
bacteria
fungi
35
Q

Which 2 tissues does the cork cambium give rise to?

A

Phelloderm
= thin layer of parenchyma cells that forms on the interior of the cork cambium

Cork cells (phellem)
= accumulates to the exterior of the cork cambium
= deposit waxy suberin in their walls + then die

36
Q

What does periderm consist of?

A

Cork cambium
Phelloderm
Cork cells

37
Q

How do spring, summer + winter wood differ?

A

Spring/Early in season = Xylem vessels w/ large diameters + thin cell walls
- maximises transports of water to new leaves

Summer/Late season = thick cell walls to provide support

Winter = no growth
- vascular cambium inactive

38
Q

What does bark consist of?

A

Al tissues external to vascular cambium

- including secondary phloem + periderm

39
Q

Wha happens as secondary growth continues?

A

Layers of secondary xylem form consisting of tracheids (gymnosperms), vessel elements + fibres

Walls os secondary xylem cells become heavily lignified

40
Q

What are tracheids?

A

type of water-conducting cell in xylem which lacks perforations in the cell wall but have pits

41
Q

What is the difference between softwoods + hardwoods?

A

Soft:
> gymnosperms
> no vessels
> few fibres

Hard:
> angiosperms
> many vessels
> fibres

42
Q

How do living cells in the stem respire if surrounded by dead cells?

A

Lenticel = porous tissue consisting of cells w/ large intercellular spaces

43
Q

What are the evolutionary advantages of secondary growth?

A

Grow taller
-> shade neighbours

Support
Water conduction
Fire resistance

Life of Earth 2 (20 decks)

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