Soil organic matter influences cerium translocation and physiological processes in kidney bean plants exposed to cerium oxide nanoparticles

Abstract

Soil organic matter plays a major role in determining the fate of the engineered nanomaterials (ENMs) in the soil matrix and effects on the residing plants. In this study, kidney bean plants were grown in soils varying in organic matter content and amended with 0-500mg/kg cerium oxide nanoparticles (nano-CeO2) under greenhouse condition. After 52days of exposure, cerium accumulation in tissues, plant growth and physiological parameters including photosynthetic pigments (chlorophylls and carotenoids), net photosynthesis rate, transpiration rate, and stomatal conductance were recorded. Additionally, catalase and ascorbate peroxidase activities were measured to evaluate oxidative stress in the tissues. The translocation factor of cerium in the nano-CeO2 exposed plants grown in organic matter enriched soil (OMES) was twice as the plants grown in low organic matter soil (LOMS). Although the leaf cover area increased by 65-111% with increasing nano-CeO2 concentration in LOMS, the effect on the physiological processes were inconsequential. In OMES leaves, exposure to 62.5-250mg/kg nano-CeO2 led to an enhancement in the transpiration rate and stomatal conductance, but to a simultaneous decrease in carotenoid contents by 25-28%. Chlorophyll a in the OMES leaves also decreased by 27 and 18% on exposure to 125 and 250mg/kg nano-CeO2. In addition, catalase activity increased in LOMS stems, and ascorbate peroxidase increased in OMES leaves of nano-CeO2 exposed plants, with respect to control. Thus, this study provides clear evidence that the properties of the complex soil matrix play decisive roles in determining the fate, bioavailability, and biological transport of ENMs in the environment.

Intergenerational responses of wheat (Triticum aestivum L.) to cerium oxide nanoparticles exposure

“…Similarly, our μXRF data is in contrast with the results from other studies on the same CeO 2 -NPs and treatment (500 mg kg −1 soil) used in this experiment which showed CeO 2 -NPs taken up in soy and kidney beans. 28,29 However, the absence of Ce particles/ aggregates inside the wheat roots, crowns and shoots at high CeO 2 -NPs concentration (500 mg kg −1 ) in the treatment and long exposure time (90 days of full life cycle) in our study strongly suggests that wheat does not take up or accumulate Ce from CeO 2 -NPs. Previous reports have also indicated root adsorption of CeO 2 -NPs and a lack of root-to-shoot translocation of Ce in wheat.…”

“…These results demonstrate that CeO 2 -NPs undergo very limited transformation in the wheat/soil system as consistently noted in previous synchrotron studies (Table S9 †). [29][30][31][32] However, this is the first study to exhibit synchrotron localization and speciation of CeO 2 -NPs in the rhizosphere (i.e. soil-root interface and areas in root vicinity).…”

Inductively coupled plasma mass spectrometry based platforms for studies involving nanoparticle effects in biological samples

“…However, the authors demonstrated that CeO 2 ‐NPs were accumulated in plant tissues. In addition, the largest amount of CeO 2 ‐NPs was found in the roots of the radish, and a small amount of NPs was transported to the upper compartments, which corroborates the information obtained in several other studies . In fact, as the root is the edible part of the vegetable, and it is in direct contact with the soil, there is concern regarding possible contamination.…”

Interactions between nanoparticles and plants: phytotoxicity and defense mechanisms

“…The Ce accumulation in fine roots and in the storage root showed that growth in loamy sand was higher than that in silty loam (Zhang, Musante, et al 2015). Kidney bean plants exposed to CeO 2 NPs for 52 days in a low organic matter soil usually possessed higher Ce concentration than the same tissues collected from an organic matter-enriched soil (Majumdar et al 2016). Likewise, different levels of phytotoxicity caused by CeO 2 NPs were found in lettuce seedlings incubated with three kinds of media, including agar (Cui et al 2014), potting mix soil and sand (Zhang et al 2017).…”