Does water diffuse out of plants?
Water does indeed diffuse out of the leaves by the process called transpiration. Because water molecules cohere to each other via chemical bonds, called hydrogen bonds, water molecules at the top of the plants are connected to water molecules in the soil much like the cars of a train. When water transpires (a diffusion process) from the leaves, other water molecules are brought closer to the root surface. This waterway is actually called the transpiration stream. Ions move in the transpiration stream much like a non-powered boat floats along a river stream. Thus, the transpiration stream brings ions from the soil water, first to the root where they must cross the plasma membrane barrier, and eventually to the leaf. At the leaf the water molecules can escape back into the atmosphere through another specialized leaf cell called a stomata. Ions, however, will be left behind.
