Root hairs in plants absorb both water and minerals from the soil through diffusion. After the water is absorbed, it moves deeper into the root layers by either of the two pathways – apoplast or symplast.
In the apoplastic movement, water travels through intercellular spaces and permeable cell walls and is interrupted by waxy, suberised casparian strips in the root endodermis.
In the symplastic movement, water travels through the cell cytoplasm and intercellular movement is through the plasmodesmata. Water movement takes down the potential gradient. As water enters the cells through the not-so-permeable cell membrane in the symplastic pathway, water movement is slower. The inner boundary of the cortex, that is, the endodermis, is impervious to water due to the presence of casparian strips. As water molecules are unable to penetrate this layer, they move to the wall regions that are not lined with casparian strips and reach the xylem cells. Therefore, it is the only pathway that allows water and solutes to reach the vascular tissues.
Water moves freely once it is inside the xylem and enters the xylem vessels and tracheids. These xylem elements are non-living and therefore, become a part of the apoplast movement, which occurs in the non-living parts of the root.
Some plants such as pinus have additional structures called mycorrhiza associated with their roots, to help in the absorption of water and minerals.