mass transport

Question 1

transpiration

Answer 1

-evaporation of water through stomata creates negative pressure in substomatal cavity
-water diffuses from surfact of leaf cell to replace water lost by evaporation
-water moves through leaf cells
-water is drawn out of the xylem
-water moves up through the xylem to replace lost water

Question 2

what is water drawn up through the xylem by

Answer 2

-cohesion
-adhesion
-hydrostatic pressure gradient

Question 3

plasmodesmata

Answer 3

channels that connect cytoplasm of adjacent plant cells

they facilitate movement of substances between plant cells

Question 4

mass flow in xylem

Answer 4

the movement of water and ions from roots to rest of the plant driven by pressure gradient and transpiration (evaporation causes negative pressure in substomatal cavity causing water to be lost from leaf cells through plasmodesmata, causing water to be drawn out of xylem, this causes hydrostatic pressure gradient in xylem, water moved up through xylem stem due to cohesion between water molecules due to intermolecular forces between them due to the polar nature of water due to covalent bonding between O and H and adhesion between water molecules and lignin xylem walls)

Question 5

why does water adhere to lignin in xylem walls

Answer 5

lignin contains hydroxyl groups that can form hydrogen bonds with water molecules

Question 6

what creates a hydrostatic pressure gradient in xylem

Answer 6

water being drawn out of xylem (to replace water lost from leaf cells that replaces water in substomatal cavity after evaporation)

Question 7

how does water move in a continuous stream

Answer 7

by cohesion between water molecules and adhesion between water molecules and ligin

Question 8

cohesion tension model

Answer 8

process of water being transported upwards through plants driven by transpiratio, cohesion and adhesion

Question 9

transpiration (again)

Answer 9

evaporation of water from leaves creating negative pressure which pulls water upwards through the xylem

unidirectional

doesnt require atp/ not dependent on active transport

Question 10

root uptake

Answer 10

as water is pulled upwards it creates a water potential gradient causing water to enter the root from the soil via osmosis

Question 11

translocation

Answer 11

collection and delivery of photosynthetic products

bi-directional

dependent on active transport

Question 12

translocation process (involves xylem)

Answer 12

-water pulled up through xylem via transpiration
-sources load organic molecules into companion cells which load them into sieve tube elements
-water potential in sieve tubes decreases
-water drawn in from xylem via osmosis
-this raises pressure potential in sieve tube
-internal pressure differences in sieve tubes drive phloem sap along sieve tubes to sink cells
-organic molecules/sucrose is unloaded into sink cells
-this increases water potential in sieve tubes in phloem
-water moves into xylem via osmosis
-carbohydrates in sink cells can be used in times of less photosynthesis due to less sunlight

Question 13

monosaccharides

Answer 13

glucose fructose galactose