Which part of a plant normally takes up water from the soil?

Water enters through the roots, and specifically through root hairs, which are thin single-cell extensions that push between soil particles and multiply the absorbing surface enormously. Water crosses into them by osmosis, moving from the wetter soil into the more concentrated cell contents. From there it travels up through xylem, a system of hollow tubes made of dead reinforced cells that runs from root to leaf. What drives the climb is mostly evaporation at the top: water escaping from the leaves through the stomata pulls on the column of water below, and because water molecules cling to one another the whole column is dragged upward. This is called the transpiration stream, and it can lift water to the top of the tallest trees without any pump. Roots also anchor the plant and absorb dissolved minerals, and in many species they partner with fungi that extend the effective reach of the root system.

A plant loses most of the water it takes up to transpiration, keeping only a small fraction for growth.