apoplast An interconnected system in plants that consists of all the cell walls and the water that exists in them (the cell wall is composed of cellulose fibres, between which are spaces filled with water). The movement of water (and dissolved ions and solutes) through the cell walls is known as the apoplast pathway. This is the main route by which water taken up by a plant travels across the root cortex to the endodermis (see also Casparian strip). Compare symplast.

apoplast Areas of a plant that lie outside the plasmalemma, such as cell walls and dead tissues of the xylem. The apoplast may represent one of the main pathways of water movement through the plant.