Uptake And Assimilation Of Ferri-cyanide By Different Species Of Plants

Ferri-cyanideisoneofthemostcommonlyfoundspeciesin cyanide-contaminated soils and groundwater.Many abiotic factors are activated in the fate and speciation of ferri-cyanide in the environment.Although there are several studies regarding phytoremediation of ferri-cyanide,relatively little is known about detailed mechanisms involved.In this study,uptake,transport and assimilation of exogenous ferri-cyanide by different species of plants was investigated.Also,the availability of exogenous cyanogenic nitrogen as supporting sources of nitrogen for plant nutrition was evaluated.Additionally,the Agilent GeneChip rice microarray was used to analyze alternations of gene expressions in rice seedlings exposed to different cyanide compounds.The main results were as follow:1.All plant species were able to effectively remove ferri-cyanide from the hydroponic solution within 24 h exposure in the absence of light.Detached roots of rice showed the fastest removal?65.8%?and assimilation?9.11?g CN/g.h?capacity.The lowest removal?20.2%?and assimilation?2.79?g CN/g.h?capacity had the soybean.The application of lanthanum chloride showed a significantly inhibitory effect on ferri-cyanide assimilation by maize and rice,whereas silver nitrate and tetraethylammonium chloride were the most sensitive inhibitors to soybean and willows,respectively.Botanical assimilation of ferri-cyanide was observed positively in responses to temperatures,in which maize was more susceptible than other selected plants.2.Willow cuttings used were all able to remove ferri-cyanide from the hydroponic solution,but the phyto-removal rate of ferri-cyanide obtained varied with willow species,in which the fast removal was by hankow willow cuttings and the lowest had the weeping willows.It was also notice that willow cutting with leaves showed higher removal capacity for ferri-cyanide than those without leaves,indicating that transpiration had a strong influence on phyto-removal of ferri-cyanide by plants.Less than 6%of the ferri-cyanide lost from the hydroponic solution was detected from plant materials as total cyanide,and roots were the major site for ferri-cyanide accumulation.Results from the calculation of mass balance revealed that a large fraction of the lost iron cyanide from the solution was assimilated by willows.Hankow willows showed significantly higher potential?9.92?g CN/g.d?for ferri-cyanide assimilation than other two willows.3.Rice seedlings were able to remove and assimilate exogenous KCN with minor accumulation in plant materials after 48 h exposure.The presence of KNO₃ or NH₄Cl in the nutrient solution as main nitrogen sources did not affect uptake and assimilation of KCN by rice seedlings.Activities of nitrate reductase and glutamine synthetase in different parts of rice seedlings were variable with KCN concentrations applied.Higher concentrations of KCN had a stronger inhibitory effect on activities of nitrate reductase than glutamine synthetase in rice seedlings.Both iron cyanides were bioavailable for rice seedlings during 48 h exposure.KNO₃-grown rice seedlings showed significantly higher assimilatory potential for both ferro-and ferri-cyanide than NH₄Cl-grown seedlings.Also,KNO₃-grown rice seedlings had significantly higher assimilatory potential for ferro-cyanide than ferri-cyanide.Sensitivity of nitrate reductase and glutamine synthetase in rice seedlings exposed to ferro-and ferri-cyanide was identical.Results indicated that to a certain level,exogenous cyanogenic nitrogen?KCN and iron cyanides?was able to play an opportunistic source of nitrogen to support rice seedling growth.4.The transcriptional profiling was conducted using Agilent 4×44 K GeneChip rice microarray to identify differentially expressed genes in different parts of rice seedlings exposed to different species of cyanide compounds.Microarray analysis showed that three species of cyanide compounds can cause alternations of gene expressions in rice seedlings,in which more differentially expressed genes was identified in the treatment with ferri-cyanide than other two species of cyanides,especially in roots.GO enrichment analysis displayed that metabolism process and activation of some enzyme activities were induced by cyanides in both roots and shoots of rice seedlings.Simultaneously,plants are able to effectively assimilate and detoxify cyanides within plant materials to minimize the negative damage.Function analysis of differentially expressed genes suggested that these genes were mainly related to defense,detoxification,pathway modification of cell wall and secondary metabolism,and transcription factors.