title: Foliar absorption of intercepted rainfall improves woody plant water status most during drought.
abstract: A large proportion of rainfall in dryland ecosystems is intercepted by plant foliage and is generally assumed to evaporate to the atmosphere or drip onto the soil surface without being absorbed. We demonstrate foliar absorption of intercepted rainfall in a widely distributed, continental dryland, woody-plant genus: Juniperus. We observed substantial improvement in plant water status, exceeding 1.0 MPa water potential for drought-stressed plants, following precipitation on an experimental plot that excluded soil water infiltration. Experiments that wetted shoots with unlabeled and with isotopically labeled water confirmed that water potential responded substantially to foliar wetting, that these responses were not attributable to re-equilibration with other portions of the xylem, and that magnitude of response increased with water stress. Foliar absorption is not included in most ecological, hydrological, and atmospheric models; has implications for interpreting plant isotopic signatures; and not only supplements water acquisition associated with increases in soil moisture that follow large or repeated precipitation events, but also enables plants to bypass soil water uptake and benefit from the majority of precipitation events, which wet foliage but do not increase soil moisture substantially. Foliar absorption of intercepted water could be more important than previously appreciated, especially during drought when water stress is greatest.
authors: School of Natural Resources, Institute for the Study of Planet Earth, and Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, Arizona 85721-0043, USA. daveb@email.arizona.edu
authors: David D
authors: DD
authors: Breshears
authors: Nathan G
authors: NG
authors: McDowell
authors: Kelly L
authors: KL
authors: Goddard
authors: Katherine E
authors: KE
authors: Dayem
authors: Scott N
authors: SN
authors: Martens
authors: Clifton W
authors: CW
authors: Meyer
authors: Karen M
authors: KM
authors: Brown
mesh_terms: D000042:Absorption; D002980:Climate; D004190:Disasters; D017753:Ecosystem; D018653:Juniperus / Q000378:metabolism*; D018515:Plant Leaves / Q000378:metabolism*; D018521:Plant Physiological Phenomena; D011891:Rain; D012987:Soil / Q000032:analysis; D013997:Time Factors; D014867:Water / Q000378:metabolism*
chemical_list: D012987:Soil; D014867:Water