Biology · May / June 2023 · Paper 42 · Question 1

it is made of (named) tissues (in a leaf) ;

(tissues), working together / for a specific (named) function(s) ;

ref to photosynthesis ;

B is the palisade (mesophyll / tissue / layer / cells) and C contains spongy (mesophyll / tissue / layer / cells) / vascular

bundles / xylem / phloem ;

any three from:

layer B

cells are, tightly / vertically, packed or columnar or few cross walls ; (cells / layer) positioned (immediately) below, layer A / the upper epidermis ;

to (maximise) light (energy) reaching, cells / chloroplasts / layer ; ref to many chloroplasts / lots of chlorophyll ;

(large) vacuole keeps the chloroplasts towards the sides of cells ; any three from:

layer C

cells are loosely packed / layer contains (interconnecting) air spaces (between cells) ;

(mesophyll / air spaces) to allow, gas exchange / diffusion of (named) gases ;

(mesophyll / air spaces) to allow evaporation (of water) from cell surfaces (into air spaces) ;

(xylem) has, thick / lignified / waterproofed / pitted, cell wall ; (xylem) (long) continuous tube / no cytoplasm / hollow or no end / cross, walls ;

(xylem) to allow transport of, water / mineral ions ;

(phloem) to allow, translocation / transport of, sucrose / sugar / amino acids ;

guard (cell) ;

gas exchange (described) / (regulation of) transpiration / AW ;

reduce water loss (through transpiration) ;

ref to preventing wilting ;

any three from:

stomata will take longer to close / reduces (stomatal) closure / reduces (stomatal) response ;

reduced, water vapour / concentration / diffusion, gradient (between the air spaces and the outside) ;

so the (guard) cells do not lose water (as, quickly / much as the first experiment) ;

the (guard) cells, stay / become, turgid or (guard) cells take longer to become flaccid ;