Foliar Sprayed Green Zinc Oxide Nanoparticles Mitigate Drought-Induced Oxidative Stress in Tomato

Abstract

This study explored the effectiveness of green zinc oxide nanoparticles (ZnO-NPs) foliar spray on tomato growth and oxidative stress relief under drought conditions. Tomato plant subjected to four water regimes (100, 75, 50, and 25% FC), and in the same while seedlings were sprayed with 25, 50, and 100 mg/L green ZnO-NPs. The results showed that tomato growth parameters reduced significantly by increasing drought stress levels, while ZnO-NPs enhanced plant growth under all studied drought levels. Out of three ZnO-NPs concentrations tested, 25 and 50 mg/L ZnO-NPs proved to be the optimum treatments for alleviating drought stress. They increased shoot and root biomass compared to untreated controls. Application of 25 and 50 mg/L ZnO-NPs enhanced shoot dry weight by about 2–2.5-fold, respectively, under severe drought conditions (25%) compared to ZnO-NPs untreated plants. The application of 25 and 50 mg/L green ZnO-NPs decreased the drought-induced oxidative stress as indicated by the reduction in malondialdehyde and hydrogen peroxide concentrations compared to untreated controls. While 100 mg/L ZnO-NPs further increased oxidative stress. The beneficial effects of ZnO-NPs were evident in the plants’ defensive state, in which the concentration of ascorbic acid, free phenols, and the activity of superoxide dismutase, catalase, and ascorbate peroxidase were maintained at higher levels compared to NPs-untreated plants. At severe drought conditions, 25 mg/L ZnO-NPs induced SOD, CAT, and APX activity by about 3.99-, 3.23-, and 2.82-fold of their corresponding controls, respectively. Likewise, at 25% FC, SOD, CAT, and APX activity increased with 50 mg/L ZnO-NPs by about 4.58-, 3.57-, and 3.25-fold consecutively compared with their respective controls. Therefore, foliar use of green ZnO-NPs at lower concentrations might be suggested as an efficient way for enhancing tomato tolerance to drought stress.

ZnO Nanoparticles Obtained by Green Synthesis as an Alternative to Improve the Germination Characteristics of L. esculentum

“…These results are due to the fact that zinc nanoparticles increase cell division and the activity of enzyme nitrate reductase, favoring root development [ 56 , 57 , 58 ]. In turn, it is worth mentioning that zinc oxide nanoparticles contribute to the productivity and tolerance to biotic and abiotic stress, since they have the ability to activate the antioxidant system in plants grown in areas with water limitations [ 59 ]. Antioxidant enzymes, such as catalase and peroxidase, are responsible for reducing biotic and abiotic stress [ 60 , 61 ].…”

The Evaluation of the Effects of Zn, and Amino Acid-Containing Foliar Fertilizers on the Physiological and Biochemical Responses of a Hungarian Fodder Corn Hybrid

“…The concentration of malondialdehyde (MDA) is usually used to present the rate of lipid peroxidation, which is a stress indicator of membrane damage [48]. The use of Zn-containing foliar fertilizers decreased the concentration of MDA and hydrogen peroxide relative to the controls under oxidative stress conditions that were induced by drought in tomatoes [49]. The MDA concentration was significantly higher 1WAT and significantly lower three WAT in all three treatments relative to the control.…”

The role of nanoparticles in plant biochemical, physiological, and molecular responses under drought stress: A review

“…DS significantly reduces the accumulation of phenolic compounds; however, NPs possess an excellent potential to improve their accumulation in plants. The exogenous supply of ZnO-NPs (25 and 50 mg/L) significantly enhanced the concentration of phenolic compounds under DS (El-Zohri et al, 2021), which in turn increased the antioxidant activities and thereby reduced MDA and H 2 O 2 accumulation (El-Zohri et al, 2021). Javed et al (2017) investigated the impact of ZnO-NPs on phenolic contents of Stevia rebaudiana, and they noted that ZnO-NPs (100 and 1000 mg/L) significantly reduced phenolic concentration.…”

“…DS induced ROS production, which damages cell membranes, causes lipid peroxidation, and increases MDA accumulation ( Das and Roychoudhury, 2014 ). The application of NPs (ZnO) significantly decreased the MDA and H 2 O 2 accumulation and maintained membrane stability which reduced the loss of essential osmolytes ( Mohamed et al., 2017 ; Sun et al., 2020 ; El-Zohri et al., 2021 ). Water deficiency substantially reduced membrane stability, efficiency of PS-II, and chlorophyll contents ( Semida et al., 2021 ).…”

“…In the same context, NPs also increase the relative abundance of Cu/Zn-SOD, APX, and CAT ( Table S3 ) under DS, which noticeably scavenge the ROS ( Sun et al., 2020 ). The application of NPs (ZnO) also improves non-enzymatic antioxidant activities (phenolic compounds, AsA) that work in coordination with antioxidant enzymes (APX, CAT, and SOD) ( El-Zohri et al., 2021 ). NPs (SiO 2 ) significantly increased non-enzymatic activities by increasing TPC, DPPH, and FRAPS activity in plants grown under DS ( Miller and Rice-Evans, 1997 ; Sutulienė et al., 2021 ).…”