Fig. 1.1 and Fig. 1.2 are photomicrographs of sections through the leaves of two different plants. Fig. 1.1 is a photomicrograph of a section through a leaf of Cornish heath, Erica vagans. [Figure 1.1] Fig. 1.2 is a photomicrograph of a section through a leaf of Himalayan cedar, Cedrus deodara. [Figure 1.2] Fig. 1.1 and Fig. 1.2 are not shown at the same magnification.

Mark scheme

Marking points from the official mark scheme (Feb/Mar 2019). The mark or mark type is shown in brackets.

1. [1] A = palisade mesophyll;
2. [1] B = epidermis ;
3. [1] C = spongy mesophyll;
4. [max 3] accept ora throughout
5. [max 3] any three from:
6. Erica v Cedrus:
7. curled / rolled, leaf (v not, curled / rolled);
8. hairs / trichomes (v no trichomes);
9. no hypodermis / AW v hypodermis / layer of cells below epidermis / layer of cells between epidermis and palisade mesophyll;
10. A ref. to two layers of outer cells in Cedrus
11. AVP;;
12. e.g. Erica has thicker cuticle
13. Erica has larger epidermal cells
14. sunken stoma visible in Cedrus
15. Cedrus has cylindrical / needle-shaped, leafA circular in (cross-) section
16. Cedrus has lower surface area to volume ratio ;
17. [max 3] any three from:
18. idea that stomata, only open during the day / open during the day and close at night ;
19. statements about gas exchange:
20. stomata open to obtain (enough) carbon dioxide for photosynthesis ;
21. A carbon dioxide not required at night
22. statement about transpiration:
23. (most) water vapour lost via open stomata ;
24. very little water (vapour) lost via cuticle ;
25. I ref. to temperature