Biosynthesis of copper nanoparticles using Solenostemma argel and their effect on enhancing salt tolerance in barley plants

Abstract

The distinctive characteristics of nanoparticles and their potential applications have been given considerable attention by scientists across different fields, particularly agriculture. However, there has been limited effort to assess the impact of copper nanoparticles (CuNPs) in modulating physiological and biochemical processes in response to salt-induced stress. This study aimed to synthesize CuNPs biologically using Solenostemma argel extract and determine their effects on morphophysiological parameters and antioxidant defense system of barley (Hordeum vulgare) under salt stress. The biosynthesized CuNPs were characterized by (UV-vis spectroscopy with Surface Plasmon Resonance at 320 nm, the crystalline nature of the formed NPs was verified via XRD, the FTIR recorded the presence of the functional groups, while TEM was confirmed the shape (spherical) and the sizes (9 to 18 nm) of biosynthesized CuNPs. Seeds of barley plants were grown in plastic pots and exposed to different levels of salt (0, 100 and 200 mM NaCl). Our findings revealed that the supplementation of CuNPs (0, 25 and 50 mg/L) to salinized barley significantly mitigate the negative impacts of salt stress and enhanced the plant growth-related parameters. High salinity level enhanced the oxidative damage by raising the concentrations of osmolytes (soluble protein, soluble sugar, and proline), malondialdehyde (MDA) and hydrogen peroxide (H₂O₂). In addition, increasing the activities of enzymatic antioxidants, total phenol, and flavonoids. Interestingly, exposing CuNPs on salt-stressed plants enhanced the plant-growth characteristics, photosynthetic pigments, and gas exchange parameters. Furthermore, CuNPs counteracted oxidative damage by lowering the accumulation of osmolytes, H₂O₂, MDA, total phenol, and flavonoids, while simultaneously enhancing the activities of antioxidant enzymes. In conclusion, the application of biosynthesized CuNPs presents a promising approach and sustainable strategy to enhance plant resistance to salinity stress, surpassing conventional methods in terms of environmental balance.

Figure 1

Photographic images of the synthesized CuNPs.

Figure 2

Characterization of biosynthesized CuNPs from S. argel leaf extract, (a) Ultraviolet–visible absorption spectrum, (b) XRD patterns, (c) Fourier-transform infrared spectroscopy (FTIR), and (d) transmission electron microscope (TEM).

Figure 3

Barley (H. vulgare) plants under NaCl stress and application of biosynthesized silver nanoparticles. (a) (shoots), (b) roots. Where, 0 (control), 1 (25 mg/L NPs), 2 (50 mg/L NPs), 3 (100 mM NaCl), 4 (25 mg/L NPs + 100 mM NaCl), 5 (50 mg/L NPs + 100 mM NaCl), 6 (100 mM NaCl), 7 (25 mg/L NPs + 200 mM NaCl), 8 (50 mg/L NPs + 200 mM NaCl).

Figure 4

The impact of CuNPs and salt-induced stress, whether applied individually or in conjunction with each other on the photosynthetic pigments contents, (a) Ch a, (b) Ch b, and (c) carotenoids in barley (H. vulgare). All the data are means of three replicates ± standard deviation. Different letters indicate significant differences between treatments according to Duncan’s multiple range test (p ≤ 0.05).

Figure 5

The impact of CuNPs and salt-induced stress, whether applied individually or in conjunction with each other on the osmolytes contents, (a) soluble proteins leaf, (b) soluble proteins root, (c) soluble sugars leaf, (d) soluble sugars root, (e) proline leaf, and (f) proline root in barley (H. vulgare). All the data are means of three replicates ± standard deviation. Different letters indicate significant differences between treatments according to Duncan’s multiple range test (p ≤ 0.05).

Figure 6

The impact of CuNPs and salt-induced stress, whether applied individually or in conjunction with each other on the hydrogen peroxide (H₂O₂) and lipid peroxidation analyses (MDA), (a) H₂O₂ leaf, (b) H₂O₂ root, (c) MDA leaf, (d) MDA root in barley (H. vulgare). All the data are means of three replicates ± standard deviation. Different letters indicate significant differences between treatments according to Duncan’s multiple range test (p ≤ 0.05).

Figure 7

The impact of CuNPs and salt-induced stress, whether applied individually or in conjunction with each other on the antioxidant enzymes activity, (a) SOD leaf, (b) SOD root, (c) CAT leaf, (d) CAT root, (e) APX leaf, (f) APX root, (g) GR leaf, and (h) GR root in barley (H. vulgare). All the data are means of three replicates ± standard deviation. Different letters indicate significant differences between treatments according to Duncan’s multiple range test (p ≤ 0.05).

Figure 8

The impact of CuNPs and salt-induced stress, whether applied individually or in conjunction with each other on the non-enzymatic antioxidant compounds, (a) TPC leaf, (b) TPC root, (c) TFC leaf, and (d) TFC root in barley (H. vulgare). All the data are means of three replicates ± standard deviation. Different letters indicate significant differences between treatments according to Duncan’s multiple range test (p ≤ 0.05).

Figure 9

Principal component analysis (PCA) of morpho-physiological characteristics of barley plants exposed to different concentrations salt stress and application of CuNPs.

Figure 10

The correlation between different morpho-physiological characteristics of barley plants exposed to different salt stress and application of CuNPs.