title: Stomatal penetration by aqueous solutions--an update involving leaf surface particles.
abstract: The recent visualization of stomatal nanoparticle uptake ended a 40-yr-old paradigm. Assuming clean, hydrophobic leaf surfaces, the paradigm considered stomatal liquid water transport to be impossible as a result of water surface tension. However, real leaves are not clean, and deposited aerosols may change hydrophobicity and water surface tension. Droplets containing NaCl, NaClO(3), (NH(4))(2) SO(4), glyphosate, an organosilicone surfactant or various combinations thereof were evaporated on stomatous abaxial and astomatous adaxial surfaces of apple (Malus domestica) leaves. The effects on photosynthesis, necrosis and biomass were determined. Observed using an environmental scanning electron microscope, NaCl and NaClO(3) crystals on hydrophobic tomato (Solanum lycopersicum) cuticles underwent several humidity cycles, causing repeated deliquescence and efflorescence of the salts. All physiological parameters were more strongly affected by abaxial than adaxial treatments. Spatial expansion and dendritic crystallization of the salts occurred and cuticular hydrophobicity was decreased more rapidly by NaClO(3) than NaCl. The results confirmed the stomatal uptake of aqueous solutions. Humidity fluctuations promote the spatial expansion of salts into the stomata. The ion-specific effects point to the Hofmeister series: chaotropic ions reduce surface tension, probably contributing to the defoliant action of NaClO(3), whereas the salt spray tolerance of coastal plants is probably linked to the kosmotropic nature of chloride ions.
authors.affiliation: Institute of Crop Science and Resource Conservation, Plant Nutrition Group, University of Bonn, Karlrobert-Kreiten-Str. 13, D-53115, Bonn, Germany.
authors.forename: Juergen
authors.initials: J
authors.lastname: Burkhardt
authors.affiliation: Institute of Crop Science and Resource Conservation, Horticultural Science Group, University of Bonn, Auf dem Hügel 6, D-53121, Bonn, Germany.
authors.forename: Sabin
authors.initials: S
authors.lastname: Basi
authors.affiliation: Institute of Crop Science and Resource Conservation, Plant Nutrition Group, University of Bonn, Karlrobert-Kreiten-Str. 13, D-53115, Bonn, Germany.
authors.forename: Shyam
authors.initials: S
authors.lastname: Pariyar
authors.affiliation: Institute of Crop Science and Resource Conservation, Horticultural Science Group, University of Bonn, Auf dem Hügel 6, D-53121, Bonn, Germany.
authors.forename: Mauricio
authors.initials: M
authors.lastname: Hunsche
mesh_terms: D000645:Ammonium Sulfate / Q000494:pharmacology; D001692:Biological Transport; D002704:Chlorates / Q000494:pharmacology; D002734:Chlorophyll / Q000378:metabolism; D005453:Fluorescence; D005998:Glycine / Q000031:analogs & derivatives / Q000494:pharmacology; D057927:Hydrophobic and Hydrophilic Interactions; D018551:Solanum lycopersicum / Q000033:anatomy & histology / Q000187:drug effects / Q000502:physiology; D027845:Malus / Q000187:drug effects / Q000502:physiology; D008855:Microscopy, Electron, Scanning / Q000379:methods; D010788:Photosynthesis; D045332:Photosystem II Protein Complex / Q000502:physiology; D010935:Plant Diseases / Q000139:chemically induced; D018515:Plant Leaves / Q000187:drug effects / Q000502:physiology* / Q000648:ultrastructure; D054046:Plant Stomata / Q000187:drug effects / Q000502:physiology* / Q000648:ultrastructure; D018526:Plant Transpiration; D012965:Sodium Chloride / Q000378:metabolism; D012996:Solutions / Q000378:metabolism; D013500:Surface Tension; D014867:Water / Q000378:metabolism*; D000097797:Glyphosate
chemical_list: D000645:Ammonium Sulfate; D002704:Chlorates; D002734:Chlorophyll; D005998:Glycine; D045332:Photosystem II Protein Complex; D012965:Sodium Chloride; D012996:Solutions; D014867:Water; D000097797:Glyphosate; C032706:sodium chlorate