PT - JOURNAL ARTICLE AU - Cynthia Gerlein-Safdi AU - Paul P.G. Gauthier AU - Kelly K. Caylor TI - Dew-induced transpiration suppression impacts the water and isotope balances of <em>Colocasia</em> leaves AID - 10.1101/178293 DP - 2017 Jan 01 TA - bioRxiv PG - 178293 4099 - http://biorxiv.org/content/early/2017/08/30/178293.short 4100 - http://biorxiv.org/content/early/2017/08/30/178293.full AB - Foliar uptake of water from the surface of leaves is common when rainfall is scarce and non-meteoric water such as dew or fog is more abundant. However, many species in more mesic environments have hydrophobic leaves that do not allow the plant to uptake water. Unlike foliar uptake, all species can benefit from dew- or fog-induced transpiration suppression, but despite its ubiquity, transpiration suppression has so far never been quantified. Here, we investigate the effect of dew-induced transpiration suppression on the water balance and the isotopic composition of leaves via a series of experiments. Characteristically hydrophobic leaves of a tropical plant, Colocasia esculenta, are misted with isotopically enriched water to reproduce dew deposition. We measure leaf water isotopes and water potential and find that misted leaves exhibit a higher water potential (p &lt; 0.05) and a more depleted water isotopic composition than misted leaves (p &lt; 0.001), suggesting a ∼30% decrease in transpiration rate (p &lt; 0.001) compared to control leaves. We propose three possible mechanisms governing the interaction of water droplets with leaf energy balance. Comparing previous studies on foliar uptake to our results, we conclude that transpiration suppression has an effect of similar amplitude, yet opposite sign to foliar uptake on leaf water isotopes.