title: Quantitative imaging of radial oxygen loss from Valisneria spiralis roots with a fluorescent planar optode.
abstract: Oxygen (O2) availability within the sediment-root interface is critical to the survival of macrophytes in O2-deficient sediment; however, our knowledge of the fine-scale impact of macrophyte roots upon the spatiotemporal dynamics of O2 is relatively limited. In this study, a non-invasive imaging technology was utilized to map O2 micro-distribution around Vallisneria spiralis. Long-term imaging results gathered during a 36day-period revealed an abundance of O2 spatiotemporal patterns ranging from 0 to 250μmolL(-1). The root-induced O2 leakage and consequent oxygenated area were stronger in the vicinity of the basal root compared to that found in the root tip. The O2 images revealed V. spiralis exhibited radial O2 loss (ROL) along the entire root, and the O2 distribution along the root length showed a high degree of small-scale spatial heterogeneity decreasing from 80% at the basal root surface to 10% at the root tip. The oxygenated zone area around the roots increased as O2 levels increased with root growth and irradiance intensities ranging from 0 to 216μmol photons m(-2)s(-1). A weak ROL measuring <20% air saturation around the basal root surface was maintained in darkness, which was presumably attributed to the O2 supply from overlying water via plant aerenchyma. The estimated total O2 release to the rhizosphere of V. spiralis was determined to range from 8.80±7.32 to 30.34±17.71nmolm(-2)s(-1), which is much higher than many other macrophyte species. This O2 release may be an important contribution to the high-capacity of V. spiralis for quickly colonizing anaerobic sediment.
authors.affiliation: State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, China.
authors.forename: Chao
authors.initials: C
authors.lastname: Han
authors.affiliation: Geological Survey of Jiangsu Province, Nanjing 210018, China.
authors.forename: Jinghua
authors.initials: J
authors.lastname: Ren
authors.affiliation: State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, China.
authors.forename: Hao
authors.initials: H
authors.lastname: Tang
authors.affiliation: State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, China. Electronic address: dxu@niglas.ac.cn.
authors.forename: Di
authors.initials: D
authors.lastname: Xu
authors.affiliation: State Key Laboratory of Pollution Control and Resource Reuse, Center for Hydroscience Research, School of the Environment, Nanjing University, Nanjing 210093, China. Electronic address: xchxie@nju.edu.cn.
authors.forename: Xianchuan
authors.initials: X
authors.lastname: Xie
mesh_terms: D031321:Hydrocharitaceae / Q000254:growth & development* / Q000378:metabolism / Q000528:radiation effects; D008027:Light; D010100:Oxygen / Q000378:metabolism*; D018517:Plant Roots / Q000254:growth & development* / Q000378:metabolism / Q000528:radiation effects
chemical_list: D010100:Oxygen
keywords: Oxygen dynamic; Planar optode; Radial oxygen loss (ROL); Rhizosphere; Vallisneria spiralis