IB Biology SL B3.2 Transport Questions

a. water is lost through the stomata/leaves by evaporation;

b. water is drawn out of xylem vessels / spongy mesophyll into leaf airspaces;

c. adhesion allows water to travel through cell walls (by capillary action) / against gravity;

d. this generates tension/pulling force/negative pressure potentials inside the xylem vessels;

e. tension/transpirational pull draws water up in the xylem;

f. cohesion ensures a continuous column of water in the xylem/OWTTE;

g. concentration gradient created in roots allowing water intake by osmosis (from soil)

Marking guidance:

MAX 5 for transpiration (marking points a,b,c,d,e,f,g,h)

a. transpiration is the loss of water from (the surface of) the leaf / through stomata;

b. loss of water by evaporation from cell walls in leaf cells causes water to be drawn from neighbouring/other cells;

c. lost water drawn out of the xylem/creates transpirational pull;

d. transpiration pull/tension draws water up the xylem;

e. cohesion is hydrogen bonding between water molecules;

f. cohesion (of water molecules) ensures a continuous column of water;

g. adhesion of water is (hydrogen bonding) between water and other polar molecules;

h. (adhesion is involved) in capillary action in soil/in plant cell walls/lignin;

Max 3 for xylem adaptation (for marking points i,j,k,l)

i. xylem (vessels) lack cell contents for unimpeded flow;

j. xylem (vessels) have lignified walls to withstand tensions;

k. xylem (vessels) have incomplete or absent end walls for unimpeded flow;

l. xylem (vessels) have pits/pores/gaps for entry and exit of water;

For i. Look for descriptions of structures or lack of structures, do not credit the
cell is dead alone as this is not a functional adaptation.

7
max