Materials on Plant Leaf Surfaces are Deliquescent in a Variety of Environments

Many materials on plant leaf surfaces are hygroscopic, and they impact foliar applied agrochemicals, foliar water uptake, gas exchange and stomatal density. Few studies are available on the nature of these substances, and we quantify how hygroscopic these materials are. Water vapor sorption experiments on twelve leaf washes were conducted and analyzed with inductively coupled plasma-optical emission spectroscopy and X-ray diffraction. Oils were found in all Eucalyptus samples studied. The leaf materials can deliquesce and form an aqueous solution in a variety of environments where plants grow, including glasshouses and by the ocean. All plant materials studied were hygroscopic. For mangroves that excrete salt to the leaf surfaces, significant sorption occurred at high humidity of a total of 316 mg ([~]0.3 mL) over 6-10 leaves. These fitted a Guggenheim, Anderson, and de Boer isotherm; mostly due to sodium chloride, though other more hygroscopic materials were also present.