Movement of Water and Mineral Salts

1. Water enters root hairs by osmosis.
2. Mineral salts are actively transported into root hairs.

1. Water moves from root hair cells to cortex cells by osmosis.
2. Continues through endodermis and pericycle to the xylem.
3. Moves upward in the xylem to the leaves and other parts of the plant.

The movement of water from the root hair to the xylem and then through the plant is a complex, highly coordinated process involving multiple mechanisms. These processes ensure that water and the dissolved minerals needed by the plant are transported efficiently from the soil to the leaves and other plant parts.

Movement of water from a root hair to the xylem

The process begins when water is absorbed by the root hair cells from the surrounding soil. Root hair cells are specialized for water absorption due to their large surface area and thin cell walls. Water enters the root hair cells through osmosis, a passive process where water moves from an area of lower solute concentration (the soil) to an area of higher solute concentration (the inside of the root cells).

Once water enters the root hair, it moves through the different layers of the root:

1. Apoplast pathway: Water moves through the cell walls and intercellular spaces of the root cells. This pathway is faster because the water doesn't need to pass through cell membranes.
2. Symplast pathway: Water moves through the cytoplasm of the cells via plasmodesmata (small channels connecting adjacent cells). This pathway involves water entering and exiting the cytoplasm of the root cells.
3. Vacuolar pathway: Water moves through the vacuoles in the root cells, entering from one cell to the next.

At the endodermis, water enters the xylem vessels, specialized tubes that transport water and minerals up the plant. The xylem is made up of several types of cells, including tracheids and vessel elements, which are long, hollow tubes with thickened cell walls. These cells are dead at maturity, allowing water to move freely through them.

Once the water reaches the xylem, it moves upward through the plant by three main mechanisms:

1. Transpirational pull,
2. Capillarity,
3. Root pressure.

Once in the xylem, the water and the mineral salts dissolved in it move up the xylem vessel by transpirational pull, capillarity and root pressure.

Transpiration occurs when water evaporates from the plant through the stomata in the leaves. As the water is lost, the mesophyll cells draw water from the xylem in the leaf which in turn draws water from the xylem in the stem. This creates a tension called transpirational pull which draws water from the roots.

This results in a continuous column of water from the roots, through the xylem to the leaves. This column of water is called transpirational stream

Transpiration stream