Chapter 36: Resource Aquisition And Transport In Vascular Plants

Question 1

Movement of Water and Minerals

Answer 1

They are pulled up from the roots by positive pressure, or tension, which is generated by evaporation of water from the leaves.

Question 2

Movement of Sugars

Answer 2

Pushed by positive pressure from where they are produced or stored to where they are needed. They can be moved both ways between leaves and roots.

Question 3

Apoplast

Answer 3

Everything external to the plasma membrane of a plant cell, including cell walls, intercellular spaces, and the space within dead structures, such as xylem vessels and tracheids

Question 4

Symplast

Answer 4

The continuum of cytosol connected by plasmodesmata between cells

Question 5

Apoplastic route

Answer 5

Water and solutes move along the continuum of cell walls and extracellular spaces

Question 6

Symplastic Route

Answer 6

Water and solutes move along the continuum of cytosol. This requires the substances to cross a plasma membrane when first entering the plant.

Question 7

Transmembrane Route

Answer 7

Water and solutes move out of one cell, across the cell wall, and into a neighboring cell. This requires the repeated crossing of plasma membranes as substances exit one cell and enter the next.

Question 8

Osmosis

Answer 8

The diffusion of free water across a selectively premeable membrane

Question 9

Water potential

Answer 9

The physical property predicting the direction in which water will flow, governed by solute concentration and applied pressure.

Water potential = solute potential + pressure potential

Question 10

Solute potential

Answer 10

A component of water potential that is proportional to the molar of its solution and that measures the effect of solutes on the direction of water movement; it can be either negative or zero

Question 11

Pressure potential

Answer 11

A component of water potential that consists of the physical pressure on a solution, which can be positive, negative, or zero

• when a solution is being withdrawn by a syringe is under negative pressure
• when it is being expelled it is under positive pressure

Question 12

Protoplast

Answer 12

The living part of a plant cell, which also includes the plasma membrane

Question 13

Turgor Pressure

Answer 13

The force directed against a plant cell wall after the influx of water and swelling of cell due to osmosis

Question 14

Aquaporin

Answer 14

A channel protein in a cellular membrane that specifically facilitates osmosis

Question 15

Bulk flow

Answer 15

The movement of fluid to a difference in presure between two locations. This is independent of solute concentration

Occurs in the vascular tissue

Long distance transport

Question 16

Endodermis

Answer 16

In plant roots, the innermost layer of the cortex that surrounds the vascular cylinder. Functions as a final checkpoint for the selective passage of materials from the cortex into the vascular cylinder

Question 17

Casparian Strip

Answer 17

A water-impermeable wing of wax in the endoermal cells of plants that blocks the passive flow of water and solutes into the stele by way of cell walls.

This means that the water and minerals must cross the selectively permeable plasma membrane of an endodermal cell

Question 18

Transport of water and minerals into the xylem

Answer 18

Water and minerals in the root cortex must enter the xylem of the vascular cylinder. They go through endodermal cells which discharge them for their protoplast to their cell wall through diffusion and active transport. The water and minerals can then be transported to tracheid and then to the shoot system.

Question 19

Xylem Sap

Answer 19

The dilute solution of water and minerals carried through vessels and tracheids. It is transported through bulk flow to the veins that branch through each leaf.

Question 20

Transpiration

Answer 20

the evaporative loss of water from a plant

Air outside the leaf has a lower water potential than the air inside the leaf so water vapor inside the leaf diffuses and exits via the stomata. This creates tension and pulls teh xylem sap up to the leaves

Question 21

Root Pressure

Answer 21

Pressure exterted in the root of plants as the result of osmosis, causing exudation from cut stems and guttation of water from leaves

Question 22

Guttation

Answer 22

The exudation of water droplets from leaves caused by root pressure in certain plants

Question 23

Cohesion Tension Hypothesis

Answer 23

Transpiration exerts pull on xylem sap, putting the sap under negative pressure, or tension, and that the cohesion of water molceules transmits this pull along the entire length of the xylem from shoots to roots.

Question 24

Role of Stomata in Regulating transpiration

Answer 24

By opening and closing stomata, gaurd cells balance the plant’s requirement to conserve water with its requirement for photosynthesis.

Stimuli for stomatal opening and closing

• light
• depletion of CO2
• Internal Clock
• Drought Stress

Question 25

Translocation

Answer 25

The transport of organic nutrients in phloem of vascular plants

Question 26

Phloem sap

Answer 26

The sugar rich solution carried through a plant’s sieve tubes

Question 27

Sugar source

Answer 27

A plant organ in which sugar is being produced by either photosynthesis or the breakdown of starch. Mature leaves are the primary sugar sources of platns

Question 28

Sugar Sink

Answer 28

A plant organ that is a net consumer or storer of sugar. Growing roots, buds, stems, and fruits are examples of sugar sinks supplied by phloem

Question 29

Bulk flow by positive pressure

Answer 29

Sugar is loaded into the sieve tube at the source. This reduced the water potential inside of the sieve element which causes it to uptake water.

The uptake of water creates positive pressure that forces the sap to flow along the tube.

The pressure is relieve by the unloading of sugar and the loss of water at the sink.

Question 30

The symplast is highly dynamic

Answer 30

Plasmodesmata can change in permeability and number.

The phloem also conducts nerve-like electrical signals that help integrate whole-plant function