The nitrate uptake and growth of wheat were more inhibited under single-layer graphene oxide stress compared to multi-layer graphene oxide.

Although the phytotoxicity of graphene-based materials has been investigated extensively, the effects of different graphene-based materials on nutrient uptake in plants remain unclear. Here, we analyzed the differences in phytotoxicity between single-layer graphene oxide (sGO) and multi-layer graphene oxide (mGO) by analyzing the growth status and nitrate (NO3-) accumulation in wheat plants at 0, 100, 200, 400, and 800 mg L-1 graphene oxide supply. Both sGO and mGO displayed concentration-dependent inhibitory effects on biomass, root length, number of lateral roots, and nitrogen (N) nutrient status. Treatment with 400 mg L-1 sGO caused 0.9-, 1.3-, and 1-fold higher reductions in NO3--N, assimilated N, and total N concentrations in roots, respectively, than mGO treatment. Analysis of root oxidative stress and in situ NO3- uptake revealed that sGO caused more significant damage to the root tip and a lower NO3- net influx rate than mGO. In addition, the expression of NO3- transporter (NRT) genes in roots, including NRT1.5, NRT2.1, NRT2.2, NRT2.3, and NRT2.4, under sGO treatment were lower than those under mGO treatment. Overall, sGO treatment induced a more severe inhibitory effect on root growth and NO3- uptake and accumulation than mGO treatment, accompanied by significant suppression of the expression of NRTs in sGO-treated roots. This study provides a physiological and molecular basis for studying the phytotoxic effects of various sizes of graphene oxide.

Abscisic acid (ABA)-importing transporter 1 (AIT1) contributes to the inhibition of Cd accumulation via exogenous ABA application in Arabidopsis.

Soil cadmium (Cd) accumulation presents risks to crop safety and productivity. However, through an exogenous application of abscisic acid (ABA), its accumulation in plants can be reduced and its toxicity mitigated, thereby providing an alternative strategy to counteract Cd contamination of arable soil. In the present study, we demonstrated that exogenous ABA application alleviates Cd-induced growth inhibition and photosynthetic damage in wild-type (Col-0) Arabidopsis plants. However, these positive effects were weakened in the ABA-importing transporter (AIT1)-deficient mutant (ait1). Through further analysis, we found that upon ABA application, the decrease in Cd level significantly differed among ait1, Col-0, and the two AIT1-overexpressing transgenic plants (AIT1ox-1 and AIT1ox-2), suggesting that AIT1 mediates the Cd-reducing effects of ABA. ABA application also inhibited the expression of IRT1, ZIP1, ZIP4, and Nramp1 in Col-0 plants subjected to Cd stress. However, significant differences among the genotypes (ait1, Col-0 and AIT1ox) were only observed in terms of IRT1 expression. Overall, our findings suggest that the suppression of Cd accumulation and restoration of plant growth by exogenous ABA require the ABA-importing activity of AIT1 to inhibit IRT1 expression.

[Research advances in physiological toxicity of graphene on plants].

Graphene is one of the most popular carbon nanomaterials that widely used in many fields due to its unique physical and chemical properties. The expanding production and application of graphene materials has led to their inputs into the environment, with increasing risks of environment and human health. Therefore, elucidating the potential toxic effects of graphene and the related mechanism are of significance to evaluate its ecological risk and bio-safety. To date, many studies have reported the physiotoxicological effects of graphene on plants. Literature showed that graphene had concentration-dependent effects on the physiological response of plants, including seed germination, growth, oxidative stress, photosynthetic characteristics, plant hormones, and metabolic processes. In the future, it is necessary to establish a widely accepted phytotoxicity evaluation system for the safe manufacture and use of graphene.

Zn stress facilitates nitrate transporter 1.1-mediated nitrate uptake aggravating Zn accumulation in Arabidopsis plants.

Describing the mechanisms of zinc (Zn) accumulation in plants is essential to counteract the effects of excessive Zn uptake in crops grown in contaminated soils. Increasing evidence suggests that there is a positive correlation between nitrate supply and Zn accumulation in plants. However, the role of the primary nitrate transporter NRT1.1 in Zn accumulation in plants remains unknown. In this study, a Zn stress-induced increase in nitrate uptake and an increase in NRT1.1 protein levels in wild-type (Col-0) Arabidopsis plants were measured using microelectrode ion flux and green fluorescent protein (GFP)/ß-glucuronidase (GUS) staining, respectively. Both agar and hydroponic cultures showed that mutants lacking the NRT1.1 function in nrt1.1 and chl1-5 (chlorate resistant 1) exhibited lower Zn levels in the roots and shoots of Zn-stressed plants than the wild-type. A lack of NRT1.1 activity also alleviated Zn-induced photosynthetic damage and growth inhibition in plants. Further, we used a rotation system with synchronous or asynchronous uptakes of nitrate and Zn to demonstrate differences in Zn levels between the Col-0 and nrt1.1/chl1-5 mutants. Significantly lower difference in Zn levels were noted in the nitrate/Zn asynchronous treatment than in the nitrate/Zn synchronous treatment. From these results, it can be concluded that NRT1.1 modulates Zn accumulation in plants via a nitrate-dependent pathway.