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Biology 223 > Chapter 36 - 3 > Flashcards

Chapter 36 - 3 Flashcards

Transpiration Drives Transport through Xylem

1
Q

An average tree transports how many gallons of water from roots to leaves daily?

A

200 gallons.

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2
Q

How does mineral and water absorption occur?

A

Root tips with root hairs make maximum absorption possible due to surface areas.

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3
Q

What do root hairs absorb?

A

Soil solution (water and other minerals and chemicals absorbed in that water)

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4
Q

Where does this soil solution go?

A

Enters hydrophillic space inside of cell walls and into root cortex.

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5
Q

Where is soil solution kept?

A

Extracellular space which increases efficiency of absorption into cells due to the collective surface area of cortex cells being greater than epidermis cells alone.

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6
Q

Does everything follow the diffusion route?

A

No, some chemicals like potassium still use active transport.

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7
Q

What vascular tissue carries water and minerals from roots to the rest of the plant?

A

Xylem.

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8
Q

Endodermis regulates transport from where?

A

From cortex to vascular cylinder and xylem.

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9
Q

What is the apoplast?

A

Extracellular fluid

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10
Q

What is symplast?

A

Collective cytoplasm

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11
Q

What is the protoplast?

A

The cytoplasm of one cell

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12
Q

What are the 3 routes to the endodermis?

A

Apoplastic route
Symplastic route
Transmembrane route

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13
Q

What is the apoplastic route?

A

Uptake of soil solution by root hairs into extracellular space which allows fluids to move through cortex.

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14
Q

What is the symplastic route?

A

Minerals and water that cross plasma membrane and enter symplast.

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15
Q

What is the transmembrane route?

A

When water and minerals can pass from apoplast into protoplast then move via symplast.

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16
Q

What is the endodermis?

A

It controls entry into stele

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17
Q

How does endodermis control entry into stele?

A

Endodermal cells connected by waxy suberin containing casparian strip.

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18
Q

What does the endodermis provide?

A

A selectively permeable barrier that only allows materials in symplast or protoplast to enter into stele. Important for keeping toxins out of vascular tissue. Also prevents reverse diffusion of materials from xylem into cortex and soil.

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19
Q

How is fluid taken into the xylem?

A

By tracheids and vessel elements then bulk transport is possible.

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20
Q

Once H2O is absorbed what are minerals calles?

A

Xylem sap

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21
Q

How does bulk flow function?

A

Xylem sap is transported to veins that branch to each leaf. Can move 15-45 meters per hour!

22
Q

What is xylem sap bulk transport driven by?

A

Transpiration

23
Q

How much water can a single maize plant move?

A

60 L of H2O during growing season.

24
Q

What will happen if transpired fluid is transpired due to dry soil?

A

It will wilt and wither and die

25
Q

What do root cells actively transport?

A

Mineral ions into the xylem.

26
Q

What do casparian strips prevent?

A

Ions from leaving to the cortex.

27
Q

What will follow minerals to maintain osmotic pressure?

A

Water H2O

28
Q

What does osmotic pressure generate?

A

Root pressure pushing xylem sap upwards which occurs at NIGHT. This can lead to guttation.

29
Q

What is guttation?

A

The forcing of H2O from leaves.

30
Q

Is root pressure a main contributor to flow of xylem sap?

A

Not at all! Very minor contributor but does occur at night in small plants.

31
Q

What is the cohesion tension hypothesis?

A

That transpiration is the physical pull of water molecules up the plant due to evaporation of water molecules. It is a chain reaction of evaportaion.

32
Q

Can dead plants continue xylem transport?

A

Yes, even after death plants can continue to transport xylem sap upwards for weeks.

33
Q

What pressure is Xylem sap?

A

Xylem sap is under negative pressure.

34
Q

Describe the transpiration pull process?

A

The process in which water is pulled up fro the roots to the leaves. It occurs because of water loss from the leaf surface through the stomata. This loss creates a negative pressure which causes water to move upward through xylem vessels. This movement is driven by cohesion and adhesion between water molecules and vessel walls.

35
Q

What is essential for transpiration pull?

A

Water inside of the leaf is essential for CO2 to react with.

36
Q

What is CO2 needed for?

A

Photosynthesis.

37
Q

What is within the mesophyll for transpiration?

A

The air is saturated with H2O. Water diffuses out of the leaf into the air through the stomata. This is transpiration. Leads to transpirational pull.

38
Q

Is there any energy imput for transpirational pull?

A

No. Sunlight warms the leaves causing transpiration. Basically xylem flow is solar powered.

39
Q

What are the 5 steps of transpirational pull? (doesn’t need to be memorized, just comprehended.)

A
  1. Water vapor diffuses from moist leaf air space to the air through stomata.
  2. Water is replaced in the air space from water film coating the mesophyll cells.
  3. Air and Water interface retreats into the cell wall increasing surface tension and rate of transpiration.
    4.Increased surface tension pulls H2O from adjacent cells.
  4. H2O from Xylem is pulled into adjacent cells to replace lost H2O.
40
Q

What is cohesion?

A

The attractive force between molecules of the same substance. In transpirational pull, the water molecules creating hydrogen bonds.

41
Q

Within the xylem what is significant about the H2O column?

A

It’s as strong as steel with a similar diameter.

42
Q

What do these hydrogen bonds allow for?

A

H2O to be pulled up like a string rather than individual molecules.
As H2O leaves the xylem the pull is relayed molecule to molecule moving units up as a whole.

43
Q

What is adhesion?

A

Attraction between H2O and polar molecules.

44
Q

Are H2O and cellulose polar or non polar?

A

Polar. This creates a strong attraction between them in the xylem. It also prevents gravity from pulling the H2O down.

45
Q

Compare and Contrast Adhesion and Cohesion.

A

Both: Involve water molecules attracting/ sticking to things. In adhesion it’s more water and in cohesion it is the xylem vessel walls. Both aid in upward movement of H2O molecules.

Cohesion: Attraction between water molecules facilitating their movement in a column. Pulls water molecules upward

Adhesion: Attraction between water molecules and vessel walls aiding in the upwards transport of water. Counters force of gravity by enabling water to adhere to xylem walls and move against water.

46
Q

What is the flow fo the xylem sap driven by?

A

Physical properties that lead to a water potential difference.

47
Q

What is the evaporation of water from leaves called?

A

Transpiration.

48
Q

Water loss lowering water and air interference creates what type of pressure?

A

Negative pressure.

49
Q

Entire solution moves together due to what?

A

Cohesion of water molecules due to hydrogen bonding.

50
Q

Xylem sap doe snot move backwards due to what?

A

the adhesion of water molecules with cellulose/Xylem walls.

51
Q
A

Biology 223 (12 decks)

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