title: Leaf gas films delay salt entry and enhance underwater photosynthesis and internal aeration of Melilotus siculus submerged in saline water.
abstract: A combination of flooding and salinity is detrimental to most plants. We studied tolerance of complete submergence in saline water for Melilotus siculus, an annual legume with superhydrophobic leaf surfaces that retain gas films when under water. M. siculus survived complete submergence of 1 week at low salinity (up to 50 mol m(-3) NaCl), but did not recover following de-submergence from 100 mol m(-3) NaCl. The leaf gas films protected against direct salt ingress into the leaves when submerged in saline water, enabling underwater photosynthesis even after 3 d of complete submergence. By contrast, leaves with the gas films experimentally removed suffered from substantial Na(+) and Cl(-) intrusion and lost the capacity for underwater photosynthesis. Similarly, plants in saline water and without gas films lost more K(+) than those with intact gas films. This study has demonstrated that leaf gas films reduce Na(+) and Cl(-) ingress into leaves when submerged by saline water - the thin gas layer physically separates the floodwater from the leaf surface. This feature aids survival of plants exposed to short-term saline submergence, as well as the previously recognized beneficial effects of gas exchange under water.
authors.affiliation: School of Plant Biology (M084), UWA Institute of Agriculture, 35 Stirling Highway, Crawley, Western Australia, 6009, Australia; Centre for Ecohydrology, The University of Western Australia, 35 Stirling Highway, Crawley, Western Australia, 6009, Australia; Graduate Research School, Edith Cowan University, 270 Joondalup Drive, Joondalup, Western Australia, 6027, Australia.
authors.forename: Natasha Lea
authors.initials: NL
authors.lastname: Teakle
authors.forename: Timothy David
authors.initials: TD
authors.lastname: Colmer
authors.forename: Ole
authors.initials: O
authors.lastname: Pedersen
mesh_terms: D000064:Acclimatization; D018533:Biomass; D002245:Carbon Dioxide / Q000378:metabolism; D002734:Chlorophyll / Q000378:metabolism; D029903:Melilotus / Q000187:drug effects / Q000502:physiology*; D010100:Oxygen / Q000378:metabolism*; D010788:Photosynthesis; D018515:Plant Leaves / Q000187:drug effects / Q000502:physiology; D018517:Plant Roots / Q000187:drug effects / Q000502:physiology; D018520:Plant Shoots / Q000187:drug effects / Q000502:physiology; D018526:Plant Transpiration; D054712:Salinity; D055049:Salt Tolerance; D012965:Sodium Chloride / Q000494:pharmacology*; D013312:Stress, Physiological; D013997:Time Factors; D014867:Water / Q000502:physiology*
chemical_list: D014867:Water; D002734:Chlorophyll; D002245:Carbon Dioxide; D012965:Sodium Chloride; D010100:Oxygen
keywords: aerenchyma; flooding tolerance; leaf Cl-; leaf K+; leaf Na+; legume; plant submergence tolerance; salinity tolerance; salt intrusion.