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Xu S.,Nanjing Agricultural University | Xu S.,CAS Institute of Botany | Zhu S.,Guizhou Rice Research Institute | Jiang Y.,Nanjing Agricultural University | And 4 more authors.
Plant and Soil | Year: 2013

Aims: This study investigated the molecular mechanism of hydrogen-rich water (HRW)-mediated enhancement of tolerance against salinity stress during rice seed germination. Methods: A combination of physiological and molecular approaches was used to study the effect of HRW on the alleviation of salinity stress. Results: A 100-mM NaCl stress caused the increase of H2 release in germinating rice seeds. With respect to samples treated with 100 mM NaCl alone, exogenous HRW pretreatments differentially attenuated the inhibition of seed germination and seedling growth caused by salinity. Further results showed that both 50 % (in particular) and 100 % concentration of HRW could activate α/β-amylase activity, thus accelerating the formation of reducing sugar and total soluble sugar. HRW also enhanced total, isozymatic activities or corresponding transcripts of antioxidant enzymes, including superoxide dismutase, catalase, and ascorbate peroxidase. These results were confirmed by the alleviation of oxidative damage, as indicated by a decrease of thiobarbituric acid reactive substances. Additionally, the ratio of potassium (K) to sodium (Na) in both the shoot and root parts was increased. Conclusions: Together, our results suggested that exogenous HRW treatment on rice seeds may be a good option to alleviate salinity stress. © 2013 Springer Science+Business Media Dordrecht.

Rothenberg S.E.,Chinese Academy of Sciences | Feng X.,Chinese Academy of Sciences | Zhou W.,Guizhou Rice Research Institute | Tu M.,Guizhou Rice Research Institute | And 2 more authors.
Science of the Total Environment | Year: 2012

Accumulation of total Hg (THg) and methylmercury (MeHg) was investigated among 50 indica rice varieties cultivated in 3 sites in Guizhou, China, classified as highly-contaminated, moderately-contaminated, and background sites. Concentrations of soil and pore water (depth: 0-2cm) THg and MeHg were poor predictors of THg and MeHg concentrations in polished white rice and bran, with significantly higher accumulation in the moderately-contaminated site compared to the other 2 sites (ANOVA, p<0.0001). Results indicated other environmental factors played a critical role in the translocation of Hg species from paddy soil to rice grain. We hypothesized alkaline conditions at the highly-contaminated site (surface water pH 11, other 2 sites pH 7.6-8.0), mitigated the uptake of Hg species by decreasing the solubility of micronutrients needed for plant growth, or by reducing the bioavailability of Hg species. White rice MeHg concentrations were associated with genotype but not inorganic Hg(II) concentrations (IHg=THG-MeHg) (MeHg: p<0.001, IHG: p=0.44), while bran MeHg and IHg concentrations were not significantly associated with genotype (p>0.05 for both analyses), indicating there may be genetic markers for the translocation of MeHg from the caryopsis to the endosperm, i.e., from the maternal to the filial tissue. Lastly, calculation of daily MeHg ingestion rates confirmed international guidelines for MeHg exposure were exceeded at the moderately-contaminated site (background: 0.013±0.0052μgkg -1d -1, n=46; highly-contaminated: 0.066±0.034μgkg -1d -1, n=49; moderately-contaminated: 0.42±0.13μgkg -1d -1, n=49). However, MeHg exposure at this site may be decreased up to 69% by cultivating low Hg-accumulating rice varieties. © 2012 Elsevier B.V.

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