title: Populus euphratica displays apoplastic sodium accumulation, osmotic adjustment by decreases in calcium and soluble carbohydrates, and develops leaf succulence under salt stress.
abstract: Populus euphratica Olivier is known to exist in saline and arid environments. In this study we investigated the physiological mechanisms enabling this species to cope with stress caused by salinity. Acclimation to increasing Na+ concentrations required adjustments of the osmotic pressure of leaves, which were achieved by accumulation of Na+ and compensatory decreases in calcium and soluble carbohydrates. The counterbalance of Na+/Ca2+ was also observed in mature leaves from field-grown P. euphratica trees exposed to an environmental gradient of increasing salinity. X-ray microanalysis showed that a primary strategy to protect the cytosol against sodium toxicity was apoplastic but not vacuolar salt accumulation. The ability to cope with salinity also included maintenance of cytosolic potassium concentrations and development of leaf succulence due to an increase in cell number and cell volume leading to sodium dilution. Decreases in apoplastic and vacuolar Ca2+ combined with suppression of calcineurin B-like protein transcripts suggest that Na+ adaptation required suppression of calcium-related signaling pathways. Significant increases in galactinol synthase and alternative oxidase after salt shock and salt adaptation point to shifts in carbohydrate metabolism and suppression of reactive oxygen species in mitochondria under salt stress.
authors.affiliation: Institut für Forstbotanik, Georg-August-Universität Göttingen, 37077 Goettingen, Germany.
authors.forename: Eric A
authors.initials: EA
authors.lastname: Ottow
authors.forename: Monika
authors.initials: M
authors.lastname: Brinker
authors.forename: Thomas
authors.initials: T
authors.lastname: Teichmann
authors.forename: Eberhard
authors.initials: E
authors.lastname: Fritz
authors.forename: Werner
authors.initials: W
authors.lastname: Kaiser
authors.forename: Mikael
authors.initials: M
authors.lastname: Brosché
authors.forename: Jaakko
authors.initials: J
authors.lastname: Kangasjärvi
authors.forename: Xiangning
authors.initials: X
authors.lastname: Jiang
authors.forename: Andrea
authors.initials: A
authors.lastname: Polle
mesh_terms: D000222:Adaptation, Physiological; D002118:Calcium / Q000378:metabolism; D050260:Carbohydrate Metabolism; D015870:Gene Expression; D017343:Genes, Plant; D006706:Homeostasis; D008969:Molecular Sequence Data; D009995:Osmosis; D009997:Osmotic Pressure; D018515:Plant Leaves / Q000502:physiology; D032107:Populus / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D011188:Potassium / Q000378:metabolism; D012964:Sodium / Q000378:metabolism; D012965:Sodium Chloride
chemical_list: D012965:Sodium Chloride; D012964:Sodium; D011188:Potassium; D002118:Calcium