The transport of water from the soil solution to the xylem of roots occurs by the apoplast and symplast pathways. Mineral ions can be transported dissolved in water.

Mark scheme

Marking points from the official mark scheme (Oct/Nov 2024). The mark or mark type is shown in brackets.

1. [4] any four from: 1 cell wall, pathway / route / AW ; R crossing membranes / passing through vacuoles / passing through cytoplasm, in context of passage to endodermis I diffuses / osmosis / active transport 2 movement (also), through intercellular spaces / in spaces between cells ; R intracellular spaces 3 named cell layer in apoplast pathway to endodermis ; e.g. epidermal cells / root hair cells cells of cortex / cortical cells / parenchyma cells must be in context of cell walls 4 cannot cross / stops at, Casparian strip (of endodermal cells) ; 5 detail ; made of, suberin or described as a, waxy / waterproof / impermeable (layer / substance / material in cell walls) 6 (overall) movement down a water potential gradient ; R ref. to osmosis / active transport context of across root or from root to xylem (owing to overall root to, leaf/atmosphere, gradient) 7 AVP ; e.g. non-living pathway / does not cross membranes, until the endodermis idea that water needs to pass across a cell (surface) membrane to control substances entering xylem
2. [3] net movement of K+ | membrane protein needed (yes or no) | ATP used (yes or no) | name of transport mechanism against the concentration gradient | yes | yes | active, transport / uptake down the concentration gradient | yes | no | facilitated diffusion one mark each correct column ;;; if no marks gained, allow one mark for a correct row