xylem

Water can also enter the root by seeping into the cell walls of the root hair cells. It can then move through these cell walls and the cell walls of other cells all the way to the centre of the root.

It can also travel in the spaces between the cells. This is called the apoplast pathway.

There are gaps in the cell walls of cortex cells. These gaps allow the cytoplasm of one cell to connect with the cytoplasm of the adjacent cell. These gaps are called plasmodesmata (singular = plasmodesma).

Water can travel from cell to cell by osmosis as just described. This is called the symplast pathway.

So water moves across the cortex by the apoplast and symplast pathways towards the xylem. Then it gets to a layer of cells called the endodermis.

Endodermis calls have a strip across their cell walls made of a waxy substance called suberin. The strip is called a Casparian strip. The Casparian strip means water can’t use the apoplast pathway when it gets to the endodermis so all the water has to go through the symplast pathway at this point. The next layer of cells, the pericycle, pumps ions into the xylem. This creates a lower water potential in the xylem so water enters the xylem by osmosis down a water potential gradient.