Imbibition

Imbibition is the adsorption of water onto the surface of dry, hydrophilic colloidal materials - substances like gum, starch, proteins, cellulose, agar and gelatin, collectively called imbibants - causing them to take up a large volume of water and swell noticeably. Everyday examples include a dry seed swelling when it is soaked, and wooden doors, window frames and furniture swelling during a humid rainy season; wheat gluten, in a particularly striking case, can imbibe as much as 300% of its own dry weight in water. A traditional technique for splitting rock even exploited this force directly - a dry wooden peg driven into a crevice, then kept wet, swells by imbibition with enough mechanical force to crack the rock precisely along the crevice line. In a growing plant, imbibition matters in two concrete ways: it drives the dramatic volume increase in a germinating seed that eventually ruptures the seed coat and lets th …