Effects of uncoated and citric acid coated cerium oxide nanoparticles, bulk cerium oxide, cerium acetate, and citric acid on tomato plants

Abstract

Little is known about the physiological and biochemical responses of plants exposed to surface modified nanomaterials. In this study, tomato (Solanum lycopersicum L.) plants were cultivated for 210days in potting soil amended with uncoated and citric acid coated cerium oxide nanoparticles (nCeO2, CA+nCeO2) bulk cerium oxide (bCeO2), and cerium acetate (CeAc). Millipore water (MPW), and citric acid (CA) were used as controls. Physiological and biochemical parameters were measured. At 500mg/kg, both the uncoated and CA+nCeO2 increased shoot length by ~9 and ~13%, respectively, while bCeO2 and CeAc decreased shoot length by ~48 and ~26%, respectively, compared with MPW (p≤0.05). Total chlorophyll, chlo-a, and chlo-b were significantly increased by CA+nCeO2 at 250mg/kg, but reduced by bCeO2 at 62.5mg/kg, compared with MPW. At 250 and 500mg/kg, nCeO2 increased Ce in roots by 10 and 7 times, compared to CA+nCeO2, but none of the treatments affected the Ce concentration in above ground tissues. Neither nCeO2 nor CA+nCeO2 affected the homeostasis of nutrient elements in roots, stems, and leaves or catalase and ascorbate peroxidase in leaves. CeAc at 62.5 and 125mg/kg increased B (81%) and Fe (174%) in roots, while at 250 and 500mg/kg, increased Ca in stems (84% and 86%, respectively). On the other hand, bCeO2 at 62.5 increased Zn (152%) but reduced P (80%) in stems. Only nCeO2 at 62.5mg/kg produced higher total number of tomatoes, compared with control and the rest of the treatments. The surface coating reduced Ce uptake by roots but did not affect its translocation to the aboveground organs. In addition, there was no clear effect of surface coating on fruit production. To our knowledge, this is the first study comparing the effects of coated and uncoated nCeO2 on tomato plants.

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

“…Differential CAT response in the shoots from kidney bean plants grown in soil with varying SOM contents validates that the CAT mimetic activity of CeO 2 is enhanced with more SOM in the growth media, due to stabilization of CeO 2 before entering the plants. In agreement with our observations in roots and leaves, Barrios et al (2015) found no effect on CAT activities in tomato plants exposed to pristine nano-CeO 2 ; however the CAT activity in the plants was increased upon exposure to more stable citric acid-coated CeO 2 . In barley leaves, CAT activity was not affected, but APOX activity increased significantly at 125-500 mg/kg nano-CeO 2 exposure in soil .…”

“…Similar to our observations in LOMS plants, previous studies on tomato, corn, cucumber and radish have also noted insignificant to slight increase in chlorophyll content on exposure to nano-CeO 2 (Wang et al, 2012;Zhao et al, 2013Zhao et al, , 2015Barrios et al, 2015;Zh). In another study, Rico et al (2015) showed that the chlorophyll content in barley leaves was increased at 125-500 mg/kg nano-CeO 2 , similar to our observations in LOMS leaves.…”

“…Similar to our observations in kidney bean plants, some previous studies have also reported inconsequential effects on overall growth of roots and shoots of cucumber (Zhao et al, 2013), corn , and wheat (Du et al, 2015). In tomato plants, Wang et al (2012) showed no significant effects on the plant length on chronic exposure to 0.1-10 mg/L nano-CeO 2 , building up to 130 mg/kg Ce in soil, Barrios et al (2015) found a decrease in stem growth at 62.5 and 125 mg/kg nano-CeO 2 ; however, at higher concentrations, there was no significant difference with respect to control. Priester et al (2012) also showed decrease in soybean shoot length at 100 and 500 mg/kg nano-CeO 2 exposure in soil.…”

Elucidating the mechanisms for plant uptake and in-planta speciation of cerium in radish (Raphanus sativus L.) treated with cerium oxide nanoparticles

“…It is well recognized that the release of cerium oxide nanoparticles (CeO 2 NPs) into the environment could pose serious risks to human health due to their potential accumulation in food crops [1,2]. Previous investigations have shown that CeO 2 NPs could be taken up by radish (Raphanus sativus L) and many other agricultural crops [3][4][5][6][7][8] and the health risks associated with the foodborne Ce depend on the physicochemical properties of Ce in plant tissues [9,10]. A few previous studies reported that Ce in plant tissues remained as CeO 2 NPs after plant uptake [11,12].…”

A non-classical route of efficient plant uptake verified with fluorescent nanoparticles and root adhesion forces investigated using AFM

“…These penetrating NPs were found to be transported both by symplastic and apoplastic modes and have shown xylem and phloem transport [23]. Furthermore, the role of NPs coating, such as with/without citrate [24], and surface charges [25,26] on plant uptake behaviour was also studied.…”