Plant Transport

Question 1

Components of water potential

Answer 1

total potential = solute potential + pressure potential

Question 2

Movement of water

Answer 2

Passive movement toward more negative total water potential

Question 3

Hypotonic solution for plants

Answer 3

Turgid cell (normal)

Question 4

Isotonic solution for plants

Answer 4

Flaccid cell (limp)

Question 5

Hypertonic solution for plants

Answer 5

Plasmolyzed cell

Question 6

Solutes’ effect on potential

Answer 6

Negative effect

Binding of water molecules

Question 7

Positive pressure’s effect on potential

Answer 7

Positive effect

Pushing water

Question 8

Solutes’ and positive pressure’s effects on water movement

Answer 8

Opposing effects on water movement (net 0)

Question 9

Negative pressure (tension)’s effect on potential

Answer 9

Negative effect

Pulling water

Question 10

Movement of water into cell

Answer 10

Water goes into cell until cell potential=solution potential

Question 11

Passive transportation

Answer 11

No energy required
Movement from high to low concentration
Simple diffusion
Facilitated diffusion: channel (charged molecules) or carrier (binds specific molecule)

Question 12

Active transportation

Answer 12

Energy required
Movement from high to low concentration
Primary active: transport directly coupled to ATP
Secondary active: solute transported using potential energy from chemiosmosis (H+ gradient)

Question 13

Positive ions moving out of cell (membrane is positively charged)

Answer 13

Can be done if the concentration gradient is greater than the charge differential

Question 14

Structural aspects of stomata

Answer 14

Guard cells attached to each other at their ends

Radially oriented microfibrils- more support on inside of cell than outside

Question 15

Mechanism of water movement in stomata

Answer 15

Pumping K+ in or out of the guard cell changes solute potential and total potential
Osmosis due to potential differences
Guard cells swell or go limp, opening or closing stomata

Question 16

Short distance transport

Answer 16

Diffusion: 3 routes
Apoplastic route (non-living parts, within cell walls)
Symplastic route (living parts, within cytoplasm)
Transmembrane route

Question 17

Casparian strip

Answer 17

Links endodermal cells in plants

Prevents passage of cations and most solutes into endodermis

Question 18

Transport of sucrose in plant cells

Answer 18

Mesophyll cell -> bundle-sheath cell -> phloem parenchyma cell OR companion cell (through cell wall)-> sieve tube element -> phloem parenchyma cell
Sucrose is cotransported against its concentration gradient with H+ from the cell wall space into the sieve tube cell

Question 19

Transport of sucrose from source cell (leaf) to sink cell (root)

Answer 19

Loading of sugar from source cell (leaf) into sieve tube (phloem)
Uptake of water: osmosis from xylem (water pressure moves sucrose from high pressure to low pressure)
Unloading of sugar from sieve tube into sink cell (storage root)
Water recycled back into xylem

Question 20

Cohesion-tension theory

Answer 20

Long distance transport in xylem: water molecules cohere to each other and adhere to the xylem walls, overcoming gravity
Works by tension (negative pressure): much lower potential at top than at bottom
Too much tension: cavitation (air bubble)