The phenomenon of exudation of water in liquid form through hydathodes is called guttation. It takes place on the margin of the leaves where the main vein ends and near the tips of the blade of some grasses and some herbaceous plants. The water that oozes out contains organic and inorganic substances.

When water is heated, it changes into water vapour. This is because, on heating, the water molecules start moving faster. The change of a liquid into a gaseous state on heating is called evaporation. The removal of the gaseous vapour form into the atmosphere takes place through water cycle.

Porins are the proteins that are lined with hydrophilic channels. These channels are present in the outer membrane of plastids, mitochondria, and some bacteria. They allow passage of small-sized proteins, even large biomolecules. Example- Aquaporins are water channels for diffusion of water molecules across the plasma membrane as per osmotic gradients.