Metal-based-oxide nanoparticles assisted the in vitro culture growth of Populus alba as micronutrients: essential metabolic processes and genetic stability

Abstract

The present study evaluates the in vitro culture growth rate of Populus alba upon using nano metal-based-oxides such as hematite (Fe₂O₃ NPs), zinc oxide (ZnO NPs), and manganese oxide (Mn₂O₃ NPs) nanoparticles as analogues of three primary micronutrients such as iron (Fe), zinc (Zn), and manganese (Mn), which exist in soil as micronutrients. Herein, the in vitro culture growth rate was investigated using three different concentrations (i.e., 20, 40, and 60 mg L^-1) of as-prepared metal oxide nanoparticles compared to the control. In addition, the as-prepared nanoparticles have been prepared via the co-precipitation method. Furthermore, the physicochemical properties were investigated using transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, and dynamic light scattering techniques. Overall, a significant difference in the biomass production-related parameters such as fresh weight, shoot length, and root length was observed compared to the control upon the treatment with micronutrient-based nano-metal-oxides (i.e., Mn₂O₃ > Fe₂O₃ > ZnO NPs, respectively). In addition, a significant increase in the root number of Populus alba plants upon their treatment with ZnO NPs was observed compared to other prepared nano-metal-oxides and the control. Also, a remarkable increase in the chlorophyll index was monitored upon the treatment with Fe₂O₃ NPs rather than the other commonly used Mn₂O₃ and ZnO NPs, respectively. Moreover, RAPD-PCR bioassays were applied, and the actual six primers showed a genetic variation percentage of 34.17%, indicating that Populus alba is highly genetically stable even in highly contaminated soil. As a result, our findings suggest an idea that indicates the ability to enhance the in vitro culture growth rate of Populus alba plants using metal oxide nanoparticles as analogous to essential micronutrients.

Fig. 1. Absorption spectra for ZnO (black line), Fe₂O₃ (red line) and Mn₂O₃ (blue line) nanoparticles.

Fig. 2. TEM micrographs of Fe₂O₃ (a and b), ZnO (c and d) and Mn₂O₃ (e and f) nanoparticles at different magnification powers.

Fig. 3. XRD patterns of ZnO (a), Fe₂O₃ (b) and Mn₂O₃ (c) nanoparticles.

Fig. 4. DLS and zeta-potential data of Fe₂O₃ (a and b), ZnO (c and d) and Mn₂O₃ (e and f) nanoparticles.

Fig. 5. FT-IR for Fe₂O₃ (a), ZnO (b) and Mn₂O₃ (c) nanoparticles.

Fig. 6. BET data including (a) adsorption/desorption isotherm and (b) pore size distribution analysis for ZnO, Fe₂O₃ and Mn₂O₃ nanoparticles.

Fig. 7. Gel electrophoresis pattern of RAPD-PCR of Populus alba treated with different nano-heavy metals. (a) Deca-12; (b) Deca-13; (c): Deca-11; (d) Deca-7; (e) Deca-4; (f) Deca-10 (M: 100-base pair ladder; 1: 20 mg L⁻¹ Fe; 2: 40 mg L⁻¹ Fe; 3: 60 mg L⁻¹ Fe; 4: 20 mg L⁻¹ Zn; 5: 40 mg L⁻¹ Zn; 6: 60 mg L⁻¹ Zn; 7: 20 mg L⁻¹ Mn; 8: 40 mg L⁻¹ Mn; 9: 60 mg L⁻¹ Mn; 10: control).

Fig. 8. Total phylogenetic tree of Populus alba treatments with different nano-heavy metals, resulted from all morphological parameters, chlorophyll index and genetic variation (1: 20 mg L⁻¹ Fe; 2: 40 mg L⁻¹ Fe; 3: 60 mg L⁻¹ Fe; 4: 20 mg L⁻¹ Zn; 5: 40 mg L⁻¹ Zn; 6: 60 mg L⁻¹ Zn; 7: 20 mg L⁻¹ Mn; 8: 40 mg L⁻¹ Mn; 9: 60 mg L⁻¹ Mn; 10: control).

Fig. 9. PCA plot showing covariance ordination and correlation based on morphology, physiology and RAPD-PCR among different nano-metal oxides treatments of Populus alba (1: 20 mg L⁻¹ Fe; 2: 40 mg L⁻¹ Fe; 3: 60 mg L⁻¹ Fe; 4: 20 mg L⁻¹ Zn; 5: 40 mg L⁻¹ Zn; 6: 60 mg L⁻¹ Zn; 7: 20 mg L⁻¹ Mn; 8: 40 mg L⁻¹ Mn; 9: 60 mg L⁻¹ Mn; 10: control).

Fig. 10. Pearson plot showing covariance ordination and correlation based on morphology and physiology among different nano-metal oxides treatments of Populus alba.