Differentiate between Apoplast and Symplast pathways of movement of water in plants
In the apoplast pathway, water is transported from root hair to xylem through the cell wall of intervening cells. Apoplastic water movement beyond the cortex is blocked by the Casparian strip of endodermal cells. Hence, the symplastic route is utilised to deliver water and ions beyond the cortex. Since the apoplast is made up of non-living components, the apoplastic route is least affected by the metabolic state of the root. The pathways of ion and water created by symplast are known as the symplastic pathway. This pathway offers resistance to the flow of water since the selective plasma membrane of the root cells handles the intake of ions and water. Moreover, the symplastic pathway is affected by the metabolic states of the root. The symplastic route occurs beyond the endodermis in plants. The endodermis contains a suberised band called the Casparian strip. The Casparian strip is impervious to water, therefore water is directed through the non-suberised wall regions and crosses the cell membrane to reach the xylem. Hence, water and other solutes enter the vascular bundle through the symplastic pathway by crossing the endodermis, since the apoplastic water movement beyond the cortex is blocked by the Casparian strip.
