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Mark Scheme

Unit Code

Page 4 of 7

2803/01

Session

Year

January

2001

Abbreviations, annotations and conventions used in the Mark Scheme

/ ; NOT )

ecf AW ora

= alternative and acceptable answers for the same marking point = separates marking points = answers which are not worthy of credit = words which are not essential to gain credit = underlining) key words which must be used to gain credit = error carried forward = alternative wording = or reverse argument

Question 3 (a)

Expected Answers

loss of water vapour / evaporation; from (aerial) surfaces of plants / leaves; diffusion (of water vapour) through, stomata / into atmosphere / AW;

(b)(i)

potometer;

(ii)

water uptake / AW; ® rate of transpiration

(iii)

cut shoot under water / make sure no air in xylem; insert shoot into potometer underwater / potometer set up under water; dry off leaves / avoid wetting leaves; all joints, air-tight / water-tight; (A) no air bubbles in potometer use, healthy / non-wilted, shoot; keep environmental conditions constant; cut stem at slanted angle; allow settling time (before taking measurements);

(c)

3 – 5 pointed star of xylem with phloem indicated between ‘arms’; xylem, phloem labelled correctly;

(d)

phloem; transports away from, leaf / source; ora for xylem

(e)

out of cell; down a water potential gradient / to lowest water potential / to most negative water potential;

Mark Scheme

Version Final

Marks

2 max

3 max

2

2

2

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