title: Higher concentrations of nanoscale zero-valent iron (nZVI) in soil induced rice chlorosis due to inhibited active iron transportation.
abstract: In this study, the effects of concentrations 0, 100, 250, 500, 750 and 1000 mg kg(-1) of nanoscale zero-valent iron (nZVI) on germination, seedlings growth, physiology and toxicity mechanisms were investigated. The results showed that nZVI had no effect on germination, but inhibited the rice seedlings growth in higher concentrations (>500 mg kg(-1) nZVI). The highest suppression rate of the length of roots and shoots reached 46.9% and 57.5%, respectively. The 1000mg kg(-1) nZVI caused the highest suppression rates for chlorophyll and carotenoids, at 91.6% and 85.2%, respectively. In addition, the activity of antioxidant enzymes was altered by the translocation of nanoparticles and changes in active iron content. Visible symptoms of iron deficiency were observed at higher concentrations, at which the active iron content decreased 61.02% in the shoots, but the active iron content not decreased in roots. Interestingly, the total and available amounts of iron in the soil were not less than those in the control. Therefore, the plants iron deficiency was not caused by (i) deficiency of available iron in the soil and (ii) restraint of the absorption that plant takes in the available iron, while induced by (ⅲ) the transport of active iron from the root to the shoot was blocked. The cortex tissues were seriously damaged by nZVI which was transported from soil to the root, these were proved by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS). This current study shows that the mechanism of iron deficiency in rice seedling was due to transport of active iron from the root to the shoot blocked, which was caused by the uptake of nZVI.
authors.affiliation: School of Chemistry and Environment, South China Normal University, Guangzhou 510006, China; Guangdong Technology Research Center for Ecological Management and Remediation of Urban Water System, Guangzhou 510006, China.
authors.forename: Jie
authors.initials: J
authors.lastname: Wang
authors.affiliation: School of Chemistry and Environment, South China Normal University, Guangzhou 510006, China; Guangdong Technology Research Center for Ecological Management and Remediation of Urban Water System, Guangzhou 510006, China. Electronic address: zhqfang@scnu.edu.cn.
authors.forename: Zhanqiang
authors.initials: Z
authors.lastname: Fang
authors.affiliation: School of Chemistry and Environment, South China Normal University, Guangzhou 510006, China; Guangdong Technology Research Center for Ecological Management and Remediation of Urban Water System, Guangzhou 510006, China.
authors.forename: Wen
authors.initials: W
authors.lastname: Cheng
authors.affiliation: School of Chemistry and Environment, South China Normal University, Guangzhou 510006, China; Guangdong Technology Research Center for Ecological Management and Remediation of Urban Water System, Guangzhou 510006, China.
authors.forename: Xiaomin
authors.initials: X
authors.lastname: Yan
authors.affiliation: Department of Science and Environmental Studies, The Hong Kong Institute of Education, Hong Kong 00852, China.
authors.forename: Pokeung Eric
authors.initials: PE
authors.lastname: Tsang
authors.affiliation: Environmental Engineering Program, Department of Civil Engineering, Auburn University, Auburn, AL 36849, USA.
authors.forename: Dongye
authors.initials: D
authors.lastname: Zhao
mesh_terms: D001692:Biological Transport; D018525:Germination / Q000187:drug effects; D007501:Iron / Q000378:metabolism / Q000633:toxicity*; D053768:Metal Nanoparticles; D012275:Oryza / Q000187:drug effects* / Q000502:physiology; D018517:Plant Roots / Q000187:drug effects / Q000502:physiology; D018520:Plant Shoots / Q000187:drug effects / Q000502:physiology; D036226:Seedlings / Q000187:drug effects / Q000502:physiology; D012987:Soil / Q000737:chemistry*
chemical_list: D012987:Soil; D007501:Iron
keywords: Active iron; Chlorosis; Nanotoxicology; Rice; nZVI