Transpiration also pulls water through the plant. This brings with it the mineral nutrients from roots to shoots. Water moves out of the leaves into the atmosphere. This exerts a pull on the water column, which brings the water up against gravity. Water gets into the plant at the roots by osmosis, and it transports dissolved mineral nutrients to the upper parts of the plant through the xylem. A fully grown tree may lose hundreds of gallons (thousands of liters) of water through its leaves on a hot, dry day. About 90% of the water that enters a plant's roots is used for this process; most of the rest is used in photosynthesis.