Chapter 36 - 3

Question 1

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

Answer 1

200 gallons.

Question 2

How does mineral and water absorption occur?

Answer 2

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

Question 3

What do root hairs absorb?

Answer 3

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

Question 4

Where does this soil solution go?

Answer 4

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

Question 5

Where is soil solution kept?

Answer 5

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

Question 6

Does everything follow the diffusion route?

Answer 6

No, some chemicals like potassium still use active transport.

Question 7

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

Answer 7

Xylem.

Question 8

Endodermis regulates transport from where?

Answer 8

From cortex to vascular cylinder and xylem.

Question 9

What is the apoplast?

Answer 9

Extracellular fluid

Question 10

What is symplast?

Answer 10

Collective cytoplasm

Question 11

What is the protoplast?

Answer 11

The cytoplasm of one cell

Question 12

What are the 3 routes to the endodermis?

Answer 12

Apoplastic route
Symplastic route
Transmembrane route

Question 13

What is the apoplastic route?

Answer 13

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

Question 14

What is the symplastic route?

Answer 14

Minerals and water that cross plasma membrane and enter symplast.

Question 15

What is the transmembrane route?

Answer 15

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

Question 16

What is the endodermis?

Answer 16

It controls entry into stele

Question 17

How does endodermis control entry into stele?

Answer 17

Endodermal cells connected by waxy suberin containing casparian strip.

Question 18

What does the endodermis provide?

Answer 18

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.

Question 19

How is fluid taken into the xylem?

Answer 19

By tracheids and vessel elements then bulk transport is possible.

Question 20

Once H2O is absorbed what are minerals calles?

Answer 20

Xylem sap

Question 21

How does bulk flow function?

Answer 21

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

Question 22

What is xylem sap bulk transport driven by?

Answer 22

Transpiration

Question 23

How much water can a single maize plant move?

Answer 23

60 L of H2O during growing season.

Question 24

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

Answer 24

It will wilt and wither and die

Question 25

What do root cells actively transport?

Answer 25

Mineral ions into the xylem.

Question 26

What do casparian strips prevent?

Answer 26

Ions from leaving to the cortex.

Question 27

What will follow minerals to maintain osmotic pressure?

Answer 27

Water H2O

Question 28

What does osmotic pressure generate?

Answer 28

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

Question 29

What is guttation?

Answer 29

The forcing of H2O from leaves.

Question 30

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

Answer 30

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

Question 31

What is the cohesion tension hypothesis?

Answer 31

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.

Question 32

Can dead plants continue xylem transport?

Answer 32

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

Question 33

What pressure is Xylem sap?

Answer 33

Xylem sap is under negative pressure.

Question 34

Describe the transpiration pull process?

Answer 34

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.

Question 35

What is essential for transpiration pull?

Answer 35

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

Question 36

What is CO2 needed for?

Answer 36

Photosynthesis.

Question 37

What is within the mesophyll for transpiration?

Answer 37

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.

Question 38

Is there any energy imput for transpirational pull?

Answer 38

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

Question 39

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

Answer 39

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.

Question 40

What is cohesion?

Answer 40

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

Question 41

Within the xylem what is significant about the H2O column?

Answer 41

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

Question 42

What do these hydrogen bonds allow for?

Answer 42

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.

Question 43

What is adhesion?

Answer 43

Attraction between H2O and polar molecules.

Question 44

Are H2O and cellulose polar or non polar?

Answer 44

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

Question 45

Compare and Contrast Adhesion and Cohesion.

Answer 45

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.

Question 46

What is the flow fo the xylem sap driven by?

Answer 46

Physical properties that lead to a water potential difference.

Question 47

What is the evaporation of water from leaves called?

Answer 47

Transpiration.

Question 48

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

Answer 48

Negative pressure.

Question 49

Entire solution moves together due to what?

Answer 49

Cohesion of water molecules due to hydrogen bonding.

Question 50

Xylem sap doe snot move backwards due to what?

Answer 50

the adhesion of water molecules with cellulose/Xylem walls.