mass transport plants

Question 1

xylem tissue function

Answer 1

transport water through stem up plant to plant leaves

Question 2

adaptions of xylem tissue

Answer 2

cells joined with no end walls forming long continuous tube so water flows as continuous column
cells less organelles easier water flow with no obstructions
thick cell walls with lignin so withstand tension
pits in side walls allow lateral water movement

Question 3

CT LEAF

Answer 3

Water lost from leave by transpiration - water evaporates from mesophyll cells into air spaces and WV diffuses through open stomata
reducing wp of mesophyll cells
so water drawn out xylem down wpg

Question 4

xylem CTT

Answer 4

1. Water lost from leaf because of transpiration
2. Lowers water potential of mesophyll
3. Water pulled up xylem (creating tension);
4. Water molecules cohere by hydrogen bonds;
5. (forming continuous) water column;
6. Adhesion of water (molecules) to walls of xylem;

Question 5

roots ctt

Answer 5

water enters root via osmosis

Question 6

how to set up potometer

Answer 6

cut shoot underwater at slant preventing water entering xylem
assemble potomètre with capillary tube end submerged in beaker of water
insert shoot underwater
ensure apparatus air and water tight
dry leaves
give time for shoot to acclimatise
shut tap to reservoir
form an air bubble and remove en of capillary tube from water

Question 7

how can photometer be used to measure rate of transpiration

Answer 7

record position of air bubble
record distance moved in certain amount of tine
calculator volume of uptake in given time
use radius of capillary tube to calc cross sectional area of water
and multiply by this by distance moved by air bubble
calc rate of water uptake - divide volume by time

Question 8

Describe how a potometer can be used to investigate the effect of a named
environmental variable on the rate of transpiration

Answer 8

carry out above and change on variable at a time wind light humidity temp
keep other variables constant

Question 9

limitations of using photometer to measure transpiration rate

Answer 9

rate of water uptake might not be same as rate of transpiration
water used for support and turgidity
water used for photo and produced in respiration
rate of movement in shoot in photometer may not be the same as the rate of movement in the whole plant
shoot in potometer has no roots whereas plant does
xylem cells are very narrow

Question 10

light intensity effect on transpiration

Answer 10

increases it
stomata open in light to let in co2 for photosynthesis
allowing water to evaporate faster
stomata close when its dark so lower transpiration rate

Question 11

temp effect on transpiration

Answer 11

increase it
water molecules - higher ke
so water evaporates faster

Question 12

wind intensity effect on transpiration

Answer 12

increase rate of transpiration
wind blows away water molecules from stomata decreases wp of air around stomata
incr WPG - water evaporates faster

Question 13

humidity

Answer 13

decrease rate of transpiration
more water in air so it has hwp
decreases wpg from leaf to air
water evaporates slower

Question 14

phloem tissue function

Answer 14

transport organic substances eg sucrose in plants

Question 15

how is phloem tissue adapted to function

Answer 15

sieve tube elements no nucleus and few organelles so easier flow of organic susbtances
end walls between cells perforated forming sieve plates
companion cells many mito high rate of respiration to make ATP for active transport of solutes

Question 16

translocation

Answer 16

movement of assimilates eg sucrose from source where made to sink where stored by mass flow

Question 17

mass flow hypothesis

Answer 17

at source sucrose AT into PST
by CC
lowers wp in sieve tubes so water enters from xylem via osmosis
increases hydrostatic pressure in sieve tubes creating a hydrostatic pressure gradient
so mass flow occurs movement from source to sink
at sink - sucrose removed by AT to be used by respiring cells or stored in storage organs

Question 18

tracer experiment

Answer 18

leaf supplied with radioactive tracer eg co2 w radioactive isotope
radio active tracer incorporated into organic substances during photosynthesis
the move around plant by translocation
movement tracked using autoradiography or geiger count

Question 19

ringing experiment

Answer 19

remove or kill phloem
budge forms on source side of ring
fluid from buldge has a high conc of sugars than below
showing sugars transported in phloem
tissue below ring die as cant get organic substances