Department of Environmental Health, College of Public Health, East Tennessee State University, Johnson City, TN 37614-1700, USA.
Sci Total Environ. 2013 May 1;452-453:321-32. doi: 10.1016/j.scitotenv.2013.02.059. Epub 2013 Mar 24.
The increasing applications of different nanomaterials in the myriad of nano-enabled products and their potential for leaching have raised considerable environmental, health and safety (EHS) concerns. As systematic studies investigating potential anomalies in the morphology and anatomy of crop plants are scarce, herein we report on the developmental responses of two agriculturally significant crop plants, maize (Zea mays L.) and cabbage (Brassica oleracea var. capitata L.), upon in vitro exposure to nanoparticles of citrate-coated silver (Citrate-nAg) and zinc oxide (nZnO). Analyses involve histology of the primary root morphology and anatomy using light microscopy, metal biouptake, moisture content, rate of germination, and root elongation. Comparative toxicity profiles of the ionic salts (AgNO3 and ZnSO4) are developed. Notably, we uncover structural changes in maize primary root cells upon exposure to Citrate-nAg, nZnO, AgNO3, and ZnSO4, possibly due to metal biouptake, suggesting potential for functional impairments in the plant growth and development. Citrate-nAg exposure results in lower Ag biouptake compared to AgNO3 treatment in maize. Microscopic evidence reveals 'tunneling-like effect' with nZnO treatment, while exposure to AgNO3 leads to cell erosion in maize root apical meristem. In maize, a significant change in metaxylem count is evident with Citrate-nAg, AgNO3, and ZnSO4 treatment, but not with nZnO treatment (p>0.1). In both maize and cabbage, measures of germination and root elongation reveal lower nanoparticle toxicity compared to free ions. As moisture data do not support osmotically-induced water stress hypothesis for explaining toxicity, we discuss other proximate mechanisms including the potential role of growth hormones and transcription factors. These findings highlight previously overlooked, anatomically significant effects of metal nanoparticles, and recommend considering detailed anatomical investigations in tandem with the standard developmental phytotoxicity assays (germination and root elongation) as the latter ones appear less sensitive for screening plant responses to nanomaterial insults.
越来越多的不同纳米材料应用于各种纳米产品中，而这些产品具有浸出的潜力，这引起了人们对环境、健康和安全（EHS）的极大关注。由于系统研究调查作物植物形态和解剖结构潜在异常的研究很少，因此在这里我们报告了两种具有重要农业意义的作物植物，玉米（Zea mays L.）和白菜（Brassica oleracea var. capitata L.），在体外暴露于柠檬酸涂层银（Citrate-nAg）和氧化锌（nZnO）纳米颗粒下的发育反应。分析包括使用光学显微镜对初生根形态和解剖结构进行组织学分析、金属生物吸收、水分含量、发芽率和根伸长率。开发了离子盐（AgNO3 和 ZnSO4）的比较毒性曲线。值得注意的是，我们发现玉米初生根细胞在暴露于 Citrate-nAg、nZnO、AgNO3 和 ZnSO4 时会发生结构变化，这可能是由于金属生物吸收，表明植物生长和发育可能存在功能障碍。与 AgNO3 处理相比，Citrate-nAg 暴露导致玉米中 Ag 的生物吸收降低。微观证据显示 nZnO 处理存在“隧道样效应”，而 AgNO3 处理导致玉米根尖分生组织细胞侵蚀。在玉米中，Citrate-nAg、AgNO3 和 ZnSO4 处理导致木质部计数明显变化，但 nZnO 处理则没有（p>0.1）。在玉米和白菜中，发芽和根伸长的测量结果表明，与游离离子相比，纳米颗粒的毒性较低。由于水分数据不支持渗透压诱导水胁迫假说来解释毒性，我们讨论了其他接近的机制，包括生长激素和转录因子的潜在作用。这些发现强调了以前被忽视的金属纳米颗粒的解剖学意义重大的影响，并建议考虑详细的解剖学研究与标准发育毒性测定（发芽和根伸长）相结合，因为后者对于筛选植物对纳米材料损伤的反应似乎不太敏感。
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