Describe how water and minerals absorbed by the roots and reach the leaves

Water and minerals are absorbed by the root hairs of a plant. Step 1: Absorption by Root Hairs Root hairs are extensions of epidermal cells in the root that greatly increase the surface area for absorption. Water enters the root hairs primarily through osmosis, moving from an area of higher water potential (in the soil) to an area of lower water potential (inside the root cells). Minerals are absorbed by active transport, which requires energy to move ions against their concentration gradient from the soil into the root cells. Step 2: Movement Across the Root Once inside the root hairs, water and minerals can move across the root cortex via two main pathways: Apoplast pathway*: Water and dissolved minerals move through the cell walls and intercellular spaces. Symplast pathway: Water and dissolved minerals move from cytoplasm to cytoplasm through plasmodesmata* (small channels connecting adjacent plant cells). Step 3: The Endodermis and Casparian Strip Before reaching the vascular cylinder (where xylem and phloem are located), water and minerals encounter the endodermis. The endodermal cells have a waxy band called the Casparian strip in their cell walls. This strip is impermeable to water and minerals, forcing them to enter the symplast pathway and pass through the plasma membrane of an endodermal cell. This ensures that the plant has selective control over which substances enter the xylem. Step 4: Entry into the Xylem After passing the endodermis, water and minerals enter the xylem, the primary water-conducting tissue in plants. Step 5: Translocation to the Leaves Water is then transported upwards through the xylem vessels from the roots to the stem and finally to the leaves. This upward movement is driven by transpiration, the evaporation of water from the leaves through small pores called stomata. The evaporation creates a negative pressure or tension (transpiration pull) that pulls the water column up from the roots. This process is known as the cohesion-tension theory.