Graphene oxide exposure suppresses nitrate uptake by roots of wheat seedlings

• Published in: Environmental pollution (1987) 2020-07, Vol.262, p.114224-114224, Article 114224
• Main Authors: Weng, Yineng, You, Yue, Lu, Qi, Zhong, Ao, Liu, Siyi, Liu, Huijun, Du, Shaoting
• Format: Article
• Language: English
• Subjects: Graphene oxide; Nitrate transporters; Nitrate uptake; Oxidative stress; Wheat
• ISSN: 0269-7491; 1873-6424
• DOI: 10.1016/j.envpol.2020.114224

Despite the large number of studies reporting the phytotoxicity of graphene-based materials, the effects of these materials on nutrient uptake in plants remain unclear. The present study showed that nitrate concentrations were significantly decreased in the roots of wheat plants treated with graphene oxide (GO) at 200–800 mg L−1. Non-invasive microelectrode measurement demonstrated that GO could significantly inhibit the net NO3− influx in the meristematic, elongation, and mature zones of wheat roots. Further analysis indicated that GO could be trapped in the root vacuoles, and that the maximal root length and the number of lateral roots were significantly reduced. Additionally, root tip whitening, creases, oxidative stress, and weakened respiration were observed. These observations indicate that GO is highly unfavorable for vigorous root growth and inhibits increase in root uptake area. At the molecular level, GO exposure caused DNA damage and inhibited the expression of most nitrate transporters (NRTs) in wheat roots, with the most significantly downregulated genes being NRT1.3, NRT1.5, NRT2.1, NRT2.3, and NRT2.4. We concluded that GO exposure decreased the root uptake area and root activity, and decreased the expression of NRTs, which may have consequently suppressed the NO3− uptake rate, leading to adverse nitrate accumulation in stressed plants. [Display omitted] •GO inhibited root elongation and reduced the number of lateral roots.•GO induced root tip whitening, creases, oxidative stress and respiration inhibition.•Reduced NO3− uptake by roots was detected in GO-stressed wheat.•GO significantly suppressed the expression levels of NRT1 and NRT2 in roots.•GO treatment caused DNA damage in wheat root cells.