Notes 5

Question 1

T or F: Natural selection favored taller plants with rough and thin appendages, multicellular branching roots, and unefficient long distance transport.

Answer 1

False: Natural selection favored taller plants with flat and broad appendages, multicellular branching roots, and efficient long distance transport.

Question 2

What huge step in evolution of plant lead to the long distance transport of water and minerals?

Answer 2

Xylem and Phloem

Question 3

Xylem transports water from ____ to _____

Answer 3

roots to shoots

Question 4

Phloem trasnports photosynetic products from ___ to _____

Answer 4

sources to where it is needed

Question 5

What is the gas taken up/released through the stomata of leaves and green stems?

Answer 5

CO2

Question 6

T or F: Phloem sap can flow both ways between shoots and roots.

Answer 6

True. Phloem sap can flow both ways between shoots and roots. It moves from sites of sugar production (leaves) or storage (roots) to sites of sugar use or storage.

Question 7

Roots exchange gasses with air spaces of soil taking in ____ and discharging ___.

Answer 7

O2, CO2

Question 8

Water and minerals are transported ___ from roots to shoots as _____ .

Answer 8

Upward, xylem sap

Question 9

What is transpiration and what does it do?

Answer 9

Transpiration, loss of water from leaves (mostly through stomata), creates a force within leaves that pulls xylem sap upwards.

Question 10

What are the 2 major pathways of transport in plants?

Answer 10

The apolast and the symplast.

Question 11

What is the apoplast?

Answer 11

A method of transport and consists of everything external to the plasma membrane. Includes cell walls, extracellular spaces, and the interior of dead cells such as vessel elements and tracheids.

Question 12

What is the symplast?

Answer 12

A method of transport that Consists of the entire mass of cytosol of all the living cells in a plant, as well as the plasmodesmata, Channels through cell walls that connect the cytoplasm of adjacent plant cells allowing water, small solutes, and larger molecules to pass between cells.

Question 13

What are 3 transport routes for water and solutes within plant tissues or organs?

Answer 13

The apoplastic route, the symplastic route, and the transmembrane route.

Question 14

Where does the apoplastic route go?

Answer 14

through cell walls and extracellular spaces

Question 15

Where does the symplastic route go?

Answer 15

Through the cytosol. substances must cross a plasma membrane once, when they first enter the plant then can move from cell to cell via plasmodesmata

Question 16

Where does the transmembrane route go?

Answer 16

across cell walls and requires repeated crossings of plasma membranes.

Question 17

The apoplast a continuum of what?

Answer 17

Apoplast is a continuum of cell walls and extracellular spaces.

Question 18

The symplast is a continuum of what?

Answer 18

Symplast is a continuum of cytosol connected by plasmodesmata.

Question 19

If a flaccid (limp) cell is placed in an eviornement with a higher solute concentration, what will happen?

Answer 19

the cell will lose water and undergo plasmolysis.

Question 20

Whats plasmolysis?

Answer 20

Plasmolysis occurs when the protoplast shrinks and pulls away from the cell wall.

Question 21

Whats the protoplast?

Answer 21

Protoplast=cytoplasm, organelles, and plasma membrane of the cell.

Question 22

If a flaccid (limp) cell is placed in an eviornement with a lower solute concentration, what will happen?

Answer 22

the cell will gain water and become turgid.

Question 23

What happens when a cell is turgid?

Answer 23

-cytosol full of water, plasma membrane presses against cell wall
-Turgid cells are firm and swollen
-Turgor loss in plants causes wilting which can be reversed when the plant is watered

Question 24

Efficient long distance transport of fluid requires what?

Answer 24

Bulk flow, movement of a fluid to a difference in pressure between two locations.

Question 25

Where does long distance bulk flow occur?

Answer 25

Long distance bulk flow occurs in tracheid and vessel systems of the xylem and sieve tube elements of phloem
Efficient movement is possible because mature tracheids and vessel elements have no cytoplasm and sieve tube elements have few organelles.

Question 26

Most absorption of water occurs where?

Answer 26

Most water and mineral absorption occurs near root tips, where root hairs are located and epidermis is permeable to water.
Root hair accounts for much of the surface area of roots and much absorption.
Root hairs absorb soil solution, water and dissolved mineral ions

Question 27

How do plants transport water and minerals from root hairs to the xylem?

Answer 27

The apoplastic route: the uptake of soil solution by hydrophilic walls of roots hair provides access to apoplast. Water and minerals diffuse into the cortex along a matrix of walls and extracellular spaces.
The symplastic route: minerals and water that cross plasma membrane of root hairs can enter symplast
The transmembrane route: as soil solution moves along apoplast some water and minerals are transported into protoplasts of cells of epidermis and cortex then inward via symplast.
Endodermis route: controlled entry to vascular cylinder. The controlled waxy casparian strip in the walls of the endodermal cells blocks passage of water and minerals. Only materials already in symplasts or entering that pathway by crossing plasma membrane of endodermal cell can detour around casparian strip and pass into vascular cylinder
Transport in xylem: endodermal cells and living cells in vascular cylinders discharge water and minerals into their watts (apoplast). Xylem vessels then transport water and minerals by bulk flow upward into the shoot system.
(REVIEW NOTES ON THIS)

Question 28

What is the endodermis?

Answer 28

The endodermis is the innermost layer of cells in the root cortex.It surrounds the vascular cylinder, and is the last checkpoint for selective passage
of minerals from the cortex into the vascular cylinder.

Question 29

Water and minerals can cross cortex via ___ or ____. Minerals already in ____ when
reach endodermis continue through plasmodesmata of endodermal cells and into vascular cylinder.

Answer 29

Water and minerals can cross cortex via symplast or apoplast. Minerals already in symplast when
reach endodermis continue through plasmodesmata of endodermal cells and into vascular cylinder.

Question 30

Minerals that reach endodermis via apoplast
encounter a barrier in the walls of each endodermal cell called what?

Answer 30

The Casparian strip. It is a belt made of waxy suberin. impervious to water and dissolved minerals

Question 31

Water and minerals can’t cross denodermis because of what? what do they do instead?

Answer 31

Water and minerals cannot cross endodermis and enter vascular cylinder via apoplast. Must cross the selectively permeable plasma membrane of an endodermal cell before entering vascular cylinder, Thus must enter symplast. Essential mineral ions
travelling via the apoplast are transported by membrane transporters into the cytosol of
endodermal cells. In this way the endodermis transports needed minerals into xylem and keeps out unneeded and toxic substances .

Question 32

Are trachied and vessel element spart of the apoplast, symplast, or transmembrane?

Answer 32

These water-conducting cells lack protoplasts so are parts of apoplast.

Question 33

Water and mineral move from where to where?

Answer 33

Water and minerals move from protoplasts of endodermal cells into their cell walls

Question 34

____ and ____ are involved in this movement from symplast to apoplast.

Answer 34

Diffusion and active transport