Chapter 35

Question 1

Transpiration

Answer 1

Water loss via evaporation from leaves when stomata are open and air surrounding leaves is drier than air inside leaves

Leaves with large amount of surface area lose large amounts of water through transpiration

Question 2

Water potential

Answer 2

Tendency of water to move from one area to another

Determines direction that water moves (from areas of high water potential to areas of low potential)

When the solute potential inside the cell and in surrounding solution is the same there is no net movement of water

Question 3

Water-potential gradient

Answer 3

High potential in soil; low potential in air

To move up plant, water moves down water-potential gradient in soil, tissues and atmosphere

Question 4

How is water absorbed into the root epidermis

Answer 4

Absorbed through osmosis

Travels through root cortex towards vascular tissues via three pathways

Transmembrane route, Apoplastic pathway, symplastic pathway

Question 5

Casparian strip

Answer 5

Ring of hydrophobic waxy compound in cell walls of endodermal cells

Blocks apoplastic pathway at endodermis and force liquids to cross the plasma membrane of endodermal cells.

Question 6

How water move from roots to shoots

Answer 6

A. Root pressure
B. Capillary action
C. Cohesion-tension

Question 7

Root pressure

Answer 7

A hypothesis that explains how water moves from roots to shoots

Stomata close at night to minimize water loss, and roots accumulate ions and H2O from soil

Creates a positive pressure that forces water up xylem

Question 8

Guttation

Answer 8

when water is secreted from the tips of the leaves of plants

Question 9

Capillarity

Answer 9

A hypothesis that explains how water moves from roots to shoots

Happens in response to 3 forces
Adhesion
Cohesion
Surface tension

Question 10

Adhesion

Answer 10

Attraction of unlike molecules

Water and solutes stick to sides of tube and results an upward pull

Question 11

Cohesion

Answer 11

Water molecules are bound together through hydrogen bonding

As a result of cohesion, as one molecule moves, it pulls up another water molecule

Question 12

Surface tension

Answer 12

When H20 molecules are being held together by cohesion

Measure of how much the molecules at the surface of the liquid are being pulled inward due cohesion

Question 13

Cohesion-tension theory

Answer 13

Leading hypothesis to explain water movement in vascular plants

1. Water vapor diffuses out of leaf
   Pressure decreases
2. Water evaporates inside leaf
3. Water is pulled out of xylem
4. Water pulled up xylem
5. Water pulled out of root cortex
6. Water diffuses from soil into root (osmosis)

Sun provides energy to move water through xylem

Question 14

Photosynthesis-transpiration

Answer 14

Balance between conserving H2O and maximizing photosynthesis

Plants from dry habitats and modified leaves have adaptations that slow transpiration to limit water loss.

Question 15

Translocation

Answer 15

Movement of sugars using bulk flow through phloem from sources to sinks

Question 16

Source

Answer 16

Tissue where sugar enters phloem

Sugar concentrations are high

Question 17

Sink

Answer 17

Tissue where sugar exits phloem

Sugar concentrations are low in sinks

This is where sugars are used or stored (roots and fruits of a plant)

Question 18

Sieve tube elements

Answer 18

Part of the phloem

Long thin cells that have perforated ends called sieve plants

Responsible for transporting sugars throughout the plant

Alive at maturity and lack secondary cell walls and nucleus

Question 19

Companion cells

Answer 19

Part of phloem

Provide materials to maintain the cytoplasm and plasma membrane of sieve-tube elements

Controls the metabolic activity of sieve tube elements

Question 20

Pressure-Flow hypothesis

Answer 20

Explains how sugars move through phloem

Pressure based on cohesion and phloem loading/unloading

Question 21

Phloem loading

Answer 21

Sugar is moved by active transport from source cells through companion cells to sieve tube members,

Water follows passively from xylem to sieve tube elements

Turgor pressure builds up in sieve tube elements in the source region

Question 22

Phloem unloading

Answer 22

Sucrose transfers into the sink from by passive or active transport

Water goes back into the xylem and turgor pressure in sieve tube elements drop due to the loss of solutes

Question 23

Result of phloem loading and unloading

Answer 23

High turgor pressure near source and low turgor pressure near sink

drives phloem
sap from source to sink via
bulk (pressure) flow

One-way flow of sucrose
& continuous loop of water
movement occurs, as water
supplied to & from xylem

Question 24

Result of phloem loading and unloading

Answer 24

High turgor pressure near source and low turgor pressure near sink

drives phloem sap from source to sink via bulk (pressure) flow

One-way flow of sucrose & continuous loop of water
movement occurs, as water supplied to & from xylem

Question 25

Turgor pressure

Answer 25

Pressure exerted by fluid in a cell that presses the cell membrane against the cell wall

Question 26

Symplastic route

Answer 26

A route where water travels from root hairs to xylem via plasmodesmata

Question 27

Transmembrane route

Answer 27

A route where water travels from root hairs to xylem via water channels (aquaporins)

Question 28

Apoplastic route

Answer 28

A route where water travels from root hairs to xylem within porous cell walls

Question 29

How sugar transported across membrane

Answer 29

Passive transport by diffusion
Active transport involving membrane proteins and ATP

Question 30

Two types of membrane proteins that facilitate passive transport by diffusion

Answer 30

Channel proteins
Carrier proteins

Question 31

Channel proteins

Answer 31

Form pores that selectively admit certain ions

Question 32

Carrier proteins

Answer 32

Responsible for the facilitated diffusion of sugars, amino acids across the plasma membranes of most cells.

bind specific molecules to be transported on one side of the membrane.

Question 33

Active transport proteins

Answer 33

Involves transport of molecules against electrochemical gradient with expenditure of ATP

Proteins involved in the process are
Pumps
Symporters
Antiporters
Proton pumps

Question 34

Pumps

Answer 34

Type of active transport

transmembrane proteins that actively move ions and/or solutes against a concentration or electrochemical gradient across biological membranes.

Question 35

Symporters (cotransporter)

Answer 35

proteins that simultaneously transport two molecules across a membrane in the same direction against the concentration gradient

Example of secondary active transport

Question 36

Antiporters (cotransporter)

Answer 36

membrane protein that transports two molecules at the same time in the opposite direction.

Example of secondary active transport

Question 37

What impact, if any, do you predict elevated CO2 levels will have on the number of stomata in leaves, and on the transpiration rate?

Answer 37

The number of stomata would decrease and the transpiration rate would decrease

Question 38

Which tissue acts as a filter on the water absorbed by root hairs?

Answer 38

Endodermis