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BIO203 > Water Acquisition > Flashcards

Water Acquisition Flashcards

1
Q

What are some examples of exception to uptake of water by roots?

A

Epiphytes, aquatic plants, parasites

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2
Q

Where does water in the soil come from?

A

Precipitation, irrigation

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3
Q

What are the two types of root systems?

A

Taproot and fibrous

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4
Q

What plants have taproots?

A

Gymnosperms, eudicots

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5
Q

What plants have fibrous systems?

A

Monocots

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6
Q

What is the uptake of water and nutrients determined by?

A

Surface area, particularly of new roots, and fungal associations

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7
Q

Identify the root systems

A

A: fibrous
B: taproot

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8
Q

Which root system is better equipped for drought? Why?

A

Taproot systems reaches deeper into soil for water.

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9
Q

What is leftover after gravitational water is drained?

A

Capillary water

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10
Q

What is the field capacity?

A

Maximum capillary water

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11
Q

What are some problems with gravitational wateR?

A

Flooding
Low O2, which diffuses faster in air than water
Poor root growth
Wilting

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12
Q

How are mangroves adapted to water?

A

Aerial roots above water to take in air

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13
Q

How is rice adapted to wateR?

A

Rice takes in air through stem and leaves, roots go through programmed cell death, providing passageways for air

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14
Q

Which holds the most capillary water and why: sand and clay

A

Sand is reltively large with small SA:V ratio, clay is the opposite. Clay thus has more capillary water, sand is more free draining

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15
Q

How does water move through soil?

A

Bulk flow

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16
Q

What is bulk flow of water through soil affected by?

A

Gaps between soil particles

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17
Q

What are the three factors of soil water potential? Which is more important?

A

Solute potential, pressure potential, matrix portential, solut potential

18
Q

What increases the SA for water uptake?

A

Root hairs

19
Q

Which parts of the root take up water? Which aids in stabilization?

A

Younger (that have root hairs) take up water, older aid in stability as they have lost their root hairs.

20
Q

What produces root hairs

A

Trichoblast

21
Q

What is the symplastic route of water movement?

A

Movement through living pars of the root

22
Q

What is the apoplastic route of water movement?

A

Through non-living parts (cell walls, intercellular spaces)

23
Q

When does water enter the root?

A

When the water potential of root cell is more negative than the water potential of the soil

24
Q

Why does removing water from the soil reduce the water potential gradient?

A
  • As water is drawn out, soil particles dry, matrix potential decreases
  • Solutes in soil become more concentrated and osmotic potential becomes more negative
  • Eventually potential of soil and root become equal, water uptake ceases (permanent wilting point of the soil)
25
Q

What is the visible sign of root pressure?

A

Dew

26
Q

What causes dew?

A

High soil water content and cool, damp atmosphere

27
Q

What is the cause of root pressure?

A
  • Shoot needs ions to support growth
  • Ions transported from soil into root, then stele
  • Exported to shoot, but accumulate in root when transpiration is low
  • Water potential gradient forms, water moves into stele, creating pressure
28
Q

What is the adequate zone?

A

Concentration of particular ion where the plant’s growth is 90% normal or above

29
Q

What is the deficiency zone?

A

Not enough of ion, growth limited below 90%

30
Q

What is the toxic zone?

A

Concentration of ions that becomes toxic, growth drops below 90%

31
Q

What is meant by some halophytes being osmatic adjusters?

A

Osmotic adjusters: exclude salt, cells produce osmotically active compounds to prevent net flow of water potential out by reducing water potential

32
Q

What is a cost of tolerating salt?

A

Slower growth

33
Q

What is meant by some halophytes being salt accumulators?

A

Sequester salt in vacuole.
Accumulate organic osmolytes in cytoplasm
Ionic balance achieved

34
Q

How do some halophytes use salt glands?

A

Salts exported to external glands or bladders on leaves, leaves are shed, lowering local salt concentrations

35
Q

What do high salt environments do to proteins?

A

Salts disrupt hydration shells around proteins, leading to denaturation

36
Q

How are proteins protected from salts?

A

Surrounded by compatible solutes that act as hydration cells.

37
Q

What are costs to tolerating salt and drought?

A
  • Moving ions requires energy
  • Root systems already require energy without drought or salt stress
  • Can reduce fitness if stress is not imposed
38
Q

How can tolerance costs be reduced?

A

Make responses inducible as opposed to constituted.

39
Q

How do plants respond to stress?

A

Change in gene expression

40
Q

What must plants be able to do to respond to stress?

A
  1. Detect stress
  2. Activate appropriate genes to produce appropriate proteins

BIO203 (12 decks)

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