-water from the soil (+ all dissolved substances) can flow through the cell walls (apoplastic transport is uncontrolled) or through the symplast (controlled by membranes)

-the plant only has direct control over the composition in spaces delimited by biomembrane (living cells)

-the sum of all protoplasts (which are connected by plasmodesma): symplasts

-all parts outside living cells (cell walls, intercellulars, dead xylem elements) are not filtered by membranes: apoplast

-central cylinder: radial vascular bundle in the centre - phloem and xylem arranged radially and without pith rays - important difference to the shoot