title: Silicon improves salt tolerance by increasing root water uptake in Cucumis sativus L.
abstract: Silicon enhances root water uptake in salt-stressed cucumber plants through up-regulating aquaporin gene expression. Osmotic adjustment is a genotype-dependent mechanism for silicon-enhanced water uptake in plants. Silicon can alleviate salt stress in plants. However, the mechanism is still not fully understood, and the possible role of silicon in alleviating salt-induced osmotic stress and the underlying mechanism still remain to be investigated. In this study, the effects of silicon (0.3 mM) on Na accumulation, water uptake, and transport were investigated in two cucumber (Cucumis sativus L.) cultivars ('JinYou 1' and 'JinChun 5') under salt stress (75 mM NaCl). Salt stress inhibited the plant growth and photosynthesis and decreased leaf transpiration and water content, while added silicon ameliorated these negative effects. Silicon addition only slightly decreased the shoot Na levels per dry weight in 'JinYou 1' but not in 'JinChun 5' after 10 days of stress. Silicon addition reduced stress-induced decreases in root hydraulic conductivity and/or leaf-specific conductivity. Expressions of main plasma membrane aquaporin genes in roots were increased by added silicon, and the involvement of aquaporins in water uptake was supported by application of aquaporin inhibitor and restorative. Besides, silicon application decreased the root xylem osmotic potential and increased root soluble sugar levels in 'JinYou 1.' Our results suggest that silicon can improve salt tolerance of cucumber plants through enhancing root water uptake, and silicon-mediated up-regulation of aquaporin gene expression may in part contribute to the increase in water uptake. In addition, osmotic adjustment may be a genotype-dependent mechanism for silicon-enhanced water uptake in plants.
authors.affiliation: College of Horticulture, Northwest A&F University, Yangling, 712100, Shaanxi, China.
authors.forename: Yong-Xing
authors.initials: YX
authors.lastname: Zhu
authors.forename: Xuan-Bin
authors.initials: XB
authors.lastname: Xu
authors.forename: Yan-Hong
authors.initials: YH
authors.lastname: Hu
authors.forename: Wei-Hua
authors.initials: WH
authors.lastname: Han
authors.forename: Jun-Liang
authors.initials: JL
authors.lastname: Yin
authors.forename: Huan-Li
authors.initials: HL
authors.lastname: Li
authors.forename: Hai-Jun
authors.initials: HJ
authors.lastname: Gong
mesh_terms: D020346:Aquaporins / Q000235:genetics / Q000378:metabolism; D001692:Biological Transport; D018533:Biomass; D002241:Carbohydrates / Q000032:analysis; D018553:Cucumis sativus / Q000187:drug effects / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D004229:Dithiothreitol / Q000494:pharmacology; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D017343:Genes, Plant; D008627:Mercuric Chloride / Q000494:pharmacology; D009995:Osmosis / Q000187:drug effects; D010788:Photosynthesis / Q000187:drug effects; D018515:Plant Leaves / Q000187:drug effects / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D018517:Plant Roots / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D054046:Plant Stomata / Q000187:drug effects / Q000502:physiology; D018526:Plant Transpiration / Q000187:drug effects; D019655:Quantitative Trait, Heritable; D055049:Salt Tolerance / Q000187:drug effects* / Q000235:genetics; D036226:Seedlings / Q000187:drug effects / Q000502:physiology; D012825:Silicon / Q000494:pharmacology*; D012964:Sodium / Q000378:metabolism; D012995:Solubility; D014867:Water / Q000378:metabolism*; D052584:Xylem / Q000187:drug effects / Q000502:physiology
chemical_list: D020346:Aquaporins; D002241:Carbohydrates; D010940:Plant Proteins; D014867:Water; D008627:Mercuric Chloride; D012964:Sodium; D004229:Dithiothreitol; D012825:Silicon