Abstract
The present study investigates ameliorative effects of nitric oxide (NO) against zinc oxide nanoparticles (ZnONPs) phytotoxicity in wheat seedlings. ZnONPs exposure hampered growth of wheat seedlings, which coincided with reduced photosynthetic efficiency (Fv/Fm and qP), due to increased accumulation of zinc (Zn) in xylem and phloem saps. However, SNP supplementation partially mitigated the ZnONPs-mediated toxicity through the modulation of photosynthetic activity and Zn accumulation in xylem and phloem saps. Further, the results reveal that ZnONPs treatments enhanced levels of hydrogen peroxide and lipid peroxidation (as malondialdehyde; MDA) due to severely inhibited activities of the following ascorbate–glutatione cycle (AsA–GSH) enzymes: ascorbate peroxidase, glutathione reductase, monodehydroascorbate reductase and dehydroascorbate reductase, and its associated metabolites ascorbate and glutathione. In contrast to this, the addition of SNP together with ZnONPs maintained the cellular functioning of the AsA–GSH cycle properly, hence lesser damage was noticed in comparison to ZnONPs treatments alone. The protective effect of SNP against ZnONPs toxicity on fresh weight (growth) can be reversed by 2-(4carboxy-2-phenyl)-4,4,5,5-tetramethyl- imidazoline-1-oxyl-3-oxide, a NO scavenger, and thus suggesting that NO released from SNP ameliorates ZnONPs toxicity. Overall, the results of the present study have shown the role of NO in the reducing of ZnONPs toxicity through the regulation of accumulation of Zn as well as the functioning of the AsA–GSH cycle.
Highlights
In recent years, nanotechnology has emerged as a scientific trend that could have benefits in many fields (González-Melendi et al, 2008; Nair et al, 2010; Gogos et al, 2012; Aziz et al, 2015, 2016; Prasad et al, 2016; Tripathi et al, 2017a,c,d)
The results show that zinc oxide nanoparticles (ZnONPs) (P < 0.05) inhibited activities of ascorbate peroxidase (APX), glutathione reductase (GR), monodehydroascorbate reductase (MDHAR), and dehydroascorbate reductase (DHAR), which resulted into reduced ratios of reduced ascorbate (AsA)/DHA and reduced glutathione (GSH)/oxidized glutathione (GSSG) (Figures 2C–F; Table 3)
The results of the present study show that there may two ways through which nitric oxide (NO) regulates ZnONPs toxicity in wheat seedlings
Summary
Nanotechnology has emerged as a scientific trend that could have benefits in many fields (González-Melendi et al, 2008; Nair et al, 2010; Gogos et al, 2012; Aziz et al, 2015, 2016; Prasad et al, 2016; Tripathi et al, 2017a,c,d). Nano forms show unique physicochemical properties, which are being used as chemical delivery agents in targeting molecules to a specific cellular organelle in plants (Monica and Cremonini, 2009; Nair et al, 2010; Subbaiah et al, 2016; Wang et al, 2016; Tripathi et al, 2017a,b). Among the variety of metal nanoparticles that are frequently used for commercial purposes, ZnONPs are the most prominent. They have been exploited in manufacturing paints, glass, plastics, lubricants, ceramics, pigments, cement, rubber, foods, and batteries (Monica and Cremonini, 2009). The results of previous studies show that ZnONPs have significant negative effects on plant productivity, which demands for developing strategies in order to mitigate ZnONPs toxicity in plants
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