Plant Transport

Question 1

What is the difference between transport in short distance and long distance?

Answer 1

short distance: diffusion or active transport

long distance: bulk flow

Question 2

What do proton pumps do?

Answer 2

create a hydrogen ion gradient that is a form of potential energy (can be harnessed to do work)
contributes to a voltage: membrane potential

Question 3

How is the membrane potential useful?

Answer 3

drives the transport of solutes into the cell

contributes to the absorption of K+ by root cells

Question 4

When do cotransport occur?

Answer 4

when a transport protein couples the diffusion of one solute H+ with the active transport of another NO-

Question 5

What is water potential?

Answer 5

a measurement that combines the effects of solute concentration and pressure
determines the direction of water movement (moves from high potential to low potential)

Question 6

What is solute potential?

Answer 6

also called the osmotic potential

proportional to the number of dissolved molecules, more solutes makes it more negative

Question 7

What is pressure potential?

Answer 7

the physical pressure on a a solution

Question 8

What is the water potential equation?

Answer 8

Psi = Psi solute + Psi pressure measured in MPa

Question 9

What are the three routes for transport?

Answer 9

Transmembrane route
Symplastic route
Apoplastic route

Question 10

What is the transmembrane route?

Answer 10

out of one cell, across a cell wall, and into another cell

Question 11

What is the symplastic route?

Answer 11

via the continuum of the cytosol

Question 12

What is the apoplastic route?

Answer 12

via the cell walls and extracellular spaces

Question 13

Where does most water and mineral absorption take place?

Answer 13

near the root tips, where the epidermis is permeable to water

Question 14

What is the Casparian Strip? What does it do?

Answer 14

a waxy strip of the endodermal wall

it blocks apoplectic transfer of minerals from the cortex to the vascular cylinder

Question 15

What does the endodermis do?

Answer 15

regulates and transports needed minerals from the soil into the xylem

Question 16

How do plants lose most of their water?

Answer 16

through transpiration, evaporation of water from the plants surface

Question 17

What is lost water replaced by?

Answer 17

replaced by bulk flow of water and minerals, called xylem sap, from the steles of roots to the stems and leaves

Question 18

How is root pressure generated?

Answer 18

at night, transpiration is low
root cells still pump mineral ions into the xylem of the vascular cylinder, lowing water potential
water flows in from the roots cortex, causes root pressure

Question 19

What is guttation?

Answer 19

water is pushed out through leaves from roots

Question 20

What is the transpiration-cohesion-tension mechanism?

Answer 20

water is pulled upward by negative pressure in the xylem
water vapor in airspaces of leaf moves down water potential gradient and exits the leaf via stomata, which lowers the Psi in the mesophyll
transpiration produces negative pressure (tension) in the leaf, which exerts a pulling force on water in the xylem, pulling water into the leaf

Question 21

How is transpirational pull facilitated?

Answer 21

by cohesion of water molecules to each other and adhesion of water molecules to the cell walls.

Question 22

What part of the plant is water attracted to?

Answer 22

cellulose in xylem cell walls

Question 23

What prevents the xylem from collapsing?

Answer 23

thick walls of trachea and vessels

Question 24

What controls the diameter of stoma?

Answer 24

guard cells

Question 25

What opens and closes the stomata?

Answer 25

changes in turgor pressure

Question 26

When is abscisic acid produced?

Answer 26

in response to water deficiency and causes the closure of stomata

Question 27

What is translocation?

Answer 27

the transport of sugars through phloem

Question 28

What is phloem sap?

Answer 28

an aqueous solution that is high in sucrose

Question 29

Where does phloem sap travel?

Answer 29

from a sugar source to a sugar sink

Question 30

What is a sugar source?

Answer 30

an organ that is a net producer of sugar, such as mature leaves

Question 31

What is a sugar sink?

Answer 31

an organ that is a net consumer or storer of sugar, such as a tuber or bulb, or any growing tissue

Question 32

What does phloem loading require?

Answer 32

active transport

Question 33

What enables cells to accumulate sucrose?

Answer 33

proton pumping and cotransport of sucrose and H+

Question 34

How does sap move in angiosperms?

Answer 34

through a sieve tube by bulk flow driven by positive pressure