Ch16-2

Question 1

Root hair cells

Answer 1

Long to provide large surface Area
Thin for short diffusion distances
Water moves in by osmosis due to higher WP in soils as inside root hair cells are dissolved sugars and amino acids

Question 2

Apoplastic pathway

Answer 2

Water passes from cell to cell through cell wall

Question 3

Symplastic pathway

Answer 3

Water travels from cell to cell through cytoplasm by osmosis
Passes through small openings called plasmodesmata

Question 4

Water movement

Answer 4

Water entering by osmosis increases WP of root hair cells
Cell now has higher WP than next cell
Water moves down WP gradient
Process repeated across cells
Loss of water from first cortical cell causes more water to move in from root hair cells by osmosis

Question 5

Water movement steps

Answer 5

Root hair cell
Cortex
Endodermis
Xylem

Question 6

Apoplastic to xylem

Answer 6

Root has casparian strip
Forces water to go through cell membrane to control which substances can enter the plant

Question 7

How substances move into xylem

Answer 7

Water travels into xylem due to AT of salts
Salts move through carrier proteins
Creating lower WP in xylem so water moves in by osmosis
Creates root pressure

Question 8

Evidence for root pressure

Answer 8

Pressure increases with rise of temperature
Metabolic inhibitors prevent AT and root pressure ceases

Question 9

Transpiration

Answer 9

Evaporation of water from leaves through the stomata
Causes more water to be drawn up by xylem

Question 10

Stomata and guard cells

Answer 10

When stomata open :
Water enters by osmosis
Guard cells turgid
When stomata close :
Water leaves guard cells
Guard cells are flaccid

Question 11

Cohesion

Answer 11

Strong H bonds between water molecules cause them to stick creating a column of water
Water pulled up xylem as result of transpiration pull

Question 12

Tension

Answer 12

Sucking force created when water evaporates from leaves through

Question 13

Evidence for cohesion tension

Answer 13

During day :
High transpiration so more tension and less pressure = tree trunk shrinks
If xylem vessel breaks down and air enters water no longer drawn up as continuous column of water broken

Question 14

Translocation

Answer 14

Process by which organic molecules and some ions are transported through the pollen

Question 15

Adaptations of phloem

Answer 15

Made of sieve tube elements
End walls perforated to form sieve tube plates
Companion cells have mitochondrion needed for energy to move dissolved substances
Movement in both directions