title: A possible new mechanism involved in ferro-cyanide metabolism by plants.
abstract: OBJECTIVE
  Ferro-cyanide is one of the commonly found species at cyanide-contaminated soils and groundwater. Unlike botanical metabolism of KCN via the β-cyanoalanine pathway, processes involved in the plant-mediated assimilation of ferro-cyanide are still unclear. The objective of this study was to investigate a possible mechanism involved in uptake and assimilation of ferro-cyanide by plants.
  
  
  METHODS
  Detached roots of plants were exposed to ferro-cyanide in a closed-dark hydroponic system amended with HgCl(2), AgNO(3), LaCl(3), tetraethylammonium chloride (TEACl), or Na(3)VO(4), respectively, at 25 ± 0.5°C for 24 h. Total CN, free CN(-), and dissolved Fe(2+) were analyzed spectrophotometrically. Activity of β-cyanoalanine synthase involved in cyanide assimilation was also assayed using detached roots of plants in vivo.
  
  
  RESULTS
  Dissociation of ferro-cyanide [Fe(II)(CN)(6)](-4) to free CN(-) and Fe(2+) in solution was negligible. The applied inhibitors did not show any significant impact on the uptake of ferro-cyanide by soybean (Glycine max L. cv. JD 1) and hybrid willows (Salix matsudana Koidz × alba L.; p > 0.05), but rice (Oryza sativa L. cv. JY 98) was more susceptible to the inhibitors compared with the controls (p < 0.05). However, TEACl had the most severe effect on the assimilation of ferro-cyanide by soybean, hybrid willows, and maize (Zea mays L. cv. PA 78; p < 0.01), whereas AgNO(3) was the most sensitive inhibitor to rice (p < 0.01). No measurable difference in β-cyanoalanine synthase activity of roots exposed to ferro-cyanide was observed compared with the control without any cyanides (p > 0.05), whereas roots exposed to KCN showed a considerable increase in enzyme activity (p < 0.05).
  
  
  CONCLUSIONS
  Plants take up Fe(2+) and CN(-) as a whole complex, and in vivo dissociation to free CN(-) is not prerequisite during the botanical assimilation of ferro-cyanide. Ferro-cyanide is likely metabolized by plants directly through an unknown pathway rather than the β-cyanoalanine pathway.
authors.affiliation: Department of Environmental Sciences and Engineering, Hunan Agricultural University, Changsha 410128, People's Republic of China. yuxiaozhang@hotmail.com
authors.forename: Xiao-Zhang
authors.initials: XZ
authors.lastname: Yu
authors.forename: Fan
authors.initials: F
authors.lastname: Li
authors.forename: Kun
authors.initials: K
authors.lastname: Li
mesh_terms: D005295:Ferrocyanides / Q000737:chemistry / Q000378:metabolism*; D018527:Hydroponics; D007811:Lanthanum / Q000494:pharmacology; D008190:Lyases / Q000378:metabolism; D049990:Membrane Transport Modulators / Q000494:pharmacology; D008627:Mercuric Chloride / Q000494:pharmacology; D012275:Oryza / Q000187:drug effects / Q000378:metabolism*; D010940:Plant Proteins / Q000378:metabolism; D018517:Plant Roots / Q000187:drug effects / Q000378:metabolism; D032108:Salix / Q000187:drug effects / Q000378:metabolism*; D012835:Silver Nitrate / Q000494:pharmacology; D013025:Glycine max / Q000187:drug effects / Q000378:metabolism*; D019789:Tetraethylammonium / Q000494:pharmacology; D014638:Vanadates / Q000494:pharmacology; D003313:Zea mays / Q000187:drug effects / Q000378:metabolism*
chemical_list: D005295:Ferrocyanides; D049990:Membrane Transport Modulators; D010940:Plant Proteins; C028521:lanthanum chloride; D014638:Vanadates; D008627:Mercuric Chloride; D019789:Tetraethylammonium; D007811:Lanthanum; D012835:Silver Nitrate; D008190:Lyases; C019955:beta-cyanoalanine synthase; C020354:hexacyanoferrate II