root pressure The pressure that forces water, absorbed from the soil, to move through the roots and up the stem of a plant. This pressure can be demonstrated by cutting a stem, from which water will exude. A manometer can be attached to a plant stem to measure the root pressure. Root pressure is believed to be due to both the osmosis of water, from the soil into the root cells, and the active pumping of salts into the xylem tissue, which maintains a concentration gradient along which the water will move. See also transpiration.

root pressure The pressure developed in the roots of some species of plants which, when the shoot is cut off, causes fluid to exude from the vascular system.