Figure 1.
Morphology of the ZnO NP samples determined by scanning (A,B) and transmission (C,D) electron microscopy. ZnO NPs, zinc oxide nanoparticles.
Figure 2.
Elemental analysis (chemical composition) by energy dispersive X-ray scattering (A) and crystalline structure by X-ray diffraction (B) of the sample ZnO NPs (Bautista-Díaz et al., 2021). ZnO NPs, zinc oxide nanoparticles.
Table 1.
Concentration of NSCs in ‘Western Schley’ pecan tree leaflets sprayed with sulphates, chelates and zinc nanoparticles.
| Treatments (200 mg · L−1) | NSCs (g · kg−1) | |||||||
|---|---|---|---|---|---|---|---|---|
| Fructose | Glucose | Sucrose | Starch | |||||
| 2019 | 2020 | 2019 | 2020 | 2019 | 2020 | 2019 | 2020 | |
| NZN (control) | 37.9 a | 34.3 a | 41.9 a | 38.0 a | 41.9 a | 43.5 a | 38.8 a | 40.2 a |
| ZnSO4 | 40.7 a | 38.5 a | 45.0 a | 42.6 a | 37.5 a | 36.7 a | 34.6 a | 34.5 a |
| Zn-EDTA | 39.3 a | 40.3 a | 43.5 a | 44.6 a | 40.8 a | 39.4 a | 37.5 a | 36.6 a |
| ZnO NPs | 39.5 a | 38.2 a | 43.6 a | 42.9 a | 36.7 a | 39.3 a | 35.7 a | 39.6 a |
Figure 3.
NSCs in ‘Western Schley’ pecan leaflets sprayed with sulphates, chelates and zinc nanoparticles. The data are means of treatments in 2019 and 2020. Bars with the same letter are not significantly different (Tukey’s test, p ≤ 0.05). Error bars represent standard deviations (n = 10). NSC, Non-structural carbohydrate; NZN, nitrazinc, containing Zn(NO3)2 and urea-ammonium nitrate fertiliser; Zn-EDTA, zinc ethylene diamine-tetra-acetic acid; ZnO NPs, zinc oxide nanoparticles; ZnSO4, zinc sulphate.
Figure 4.
Yield, nut weight and kernel percentage in ‘Western Schley’ pecan trees with the application of sulphates, chelates and zinc nanoparticles. The data are means of treatments in 2019 and 2020. Bars with the same letter are not significantly different (Tukey’s test, p ≤ 0.05). Error bars represent standard deviations (n = 10). NZN, nitrazinc, containing Zn(NO3)2 and urea-ammonium nitrate fertiliser; Zn-EDTA, zinc ethylene diamine-tetra-acetic acid; ZnO NPs, zinc oxide nanoparticles; ZnSO4, zinc sulphate.
Table 2.
Yield, nut weight and kernel percentage in ‘Western Schley’ pecan tree leaflets sprayed with sulphates, chelates and zinc nanoparticles.
| Treatments (200 mg · L−1) | Nut quality | |||||
|---|---|---|---|---|---|---|
| Yield (kg per tree) | Nut weight (g · kg 1 FW) | Kernel (%) | ||||
| 2019 | 2020 | 2019 | 2020 | 2019 | 2020 | |
| NZN (control) | 9.9 a | 15.6 b | 156.1 a | 166.1 b | 52.2 a | 53.0 a |
| ZnSO4 | 9.1 a | 14.1 b | 153.4 a | 167.4 b | 60.4 a | 58.0 a |
| Zn-EDTA | 8.7 a | 14.9 b | 152.5 a | 164.5 b | 54.3 a | 54.3 a |
| ZnO NPs | 9.9 a | 14.5 b | 158.6 a | 166.6 b | 54.9 a | 54.5 a |
Table 3.
Nutrient concentrations in ‘Western Schley’ pecan tree leaflets sprayed with sulphates, chelates and zinc nanoparticles.
| Treatments (200 mg · L−1) | Concentration (g · kg−1) | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Total-N | Total-P | K+ | Ca2+ | Mg2+ | ||||||
| 2019 | 2020 | 2019 | 2020 | 2019 | 2020 | 2019 | 2020 | 2019 | 2020 | |
| NZN (control) | 27.9 a | 23.9 b | 2.7 a | 2.0 b | 19.7 a | 17.6 a | 33.66 a | 28.32 b | 4.8 a | 4.1 b |
| ZnSO4 | 26.3 a | 27.3 a | 2.1 a | 1.7 b | 19.24 a | 20.3 a | 31.62 a | 33.10 a | 3.9 a | 4.3 a |
| Zn-EDTA | 24.7 a | 25.4 a | 2.7 a | 1.8 b | 17.0 a | 22.2 b | 31.10 a | 32.14 a | 3.8 a | 4.4 a |
| ZnO NPs | 24.3 a | 25.9 a | 2.5 a | 1.9 b | 21.4 a | 19.4 a | 30.30 a | 31.14 a | 4.3 a | 4.1 a |
| Concentration (mg · kg−1) | ||||||||||
| Fe2+ | Cu2+ | Mn2+ | Zn2+ | |||||||
| NZN (control) | 139.4 a | 181.9 b | 6.3 a | 5.8 b | 231.0 a | 212.4 b | 48.5 a | 45.3 a | ||
| ZnSO4 | 154.9 a | 191.6 b | 6.4 a | 6.2 a | 236.8 a | 233.8 a | 39.6 a | 40.4 a | ||
| Zn-EDTA | 160.8 a | 194.5 a | 6.5 a | 6.3 a | 242.4 a | 236.0 a | 35.8 a | 38.0 b | ||
| ZnO NPs | 118.3 a | 179.4 b | 6.2 a | 6.6 b | 227.8 a | 241.0 b | 39.3 a | 35.8 b | ||
Figure 5.
(A) Micronutrient concentrations in ‘Western Schley’ pecan tree leaflets sprayed with sulphates, chelates and zinc nanoparticles. Bars with the same letter are not significantly different (Tukey’s test,p ≤ 0.05). Error bars represent standard deviations (n = 10). NZN, nitrazinc, containing Zn(NO3)2 and urea–ammonium nitrate fertiliser; Zn-EDTA, zinc ethylene diamine-tetra-acetic acid; ZnO NPs, zinc oxide nanoparticles; ZnSO4, zinc sulphate. (B) Micronutrient concentration in ‘Western Schley’ pecan trees with the application of sulphates, chelates and zinc nanoparticles. Bars with the same letter are not significantly different (Tukey’s test, p ≤ 0.05). Error bars represent standard deviations (n = 10). NZN, nitrazinc, containing Zn(NO3)2 and urea-ammonium nitrate fertiliser; Zn-EDTA, zinc ethylene diamine-tetra-acetic acid; ZnO NPs, zinc oxide nanoparticles; ZnSO4, zinc sulphate.
Table 4.
Oxidative metabolism and AC in ‘Western Schley’ pecan tree leaflets sprayed with sulphates, chelates and zinc nanoparticles.
| Treatments (200 mg · L−1) | SOD | H2O2 | CAT | GPx | AC |
|---|---|---|---|---|---|
| NZN (control) | 1.4 a | 0.4 a | 3.5 a | 3.2 b | 83.1 a |
| ZnSO4 | 1.3 ab | 0.3 b | 2.3 b | 5.6 a | 80.6 a |
| Zn-EDTA | 1.2 c | 0.4 b | 2.3 b | 5.2 a | 76.9 b |
| ZnO NPs | 1.3 b | 0.3 b | 2.4 b | 5.3 a | 82.6 a |
1 Means in the same column followed by the same letters were not significantly different (Tukey’s test, p ≤ 0.05).
2 AC, antioxidant capacity (% of DPPH inhibition); CAT, catalase (nmol GSH · min−1 · g−1); DPPH, 2,2-diphenyl-1-picrylhydrazyl; GPx, guaiacol peroxidase (μmol GSH · min−1 · g−1); H2O2, hydrogen peroxide (μmol · g−1); ZnO NPs, zinc oxide nanoparticles; NZN, nitrazinc, containing Zn(NO3)2 and urea-ammonium nitrate fertiliser; SOD, superoxide dismutase (units · min−1 · g−1); Zn-EDTA, zinc ethylene diamine-tetra-acetic acid; ZnSO4, zinc sulphate.
Table 5.
Concentration of photosynthetic pigments and phenolic compounds in ‘Western Schley’ pecan tree leaflets sprayed with sulphates, chelates and zinc nanoparticles.
| Treatments (200 mg · L−1) | TChl (μg · g−1) | TC (μg · g−1) | TFl (mg GAE · g−1) | TP (mg QE · g−1) |
|---|---|---|---|---|
| NZN (control) | 45.1 a | 14.7 a | 55.7 a | 18.4 a |
| ZnSO4 | 45.5 a | 10.5 b | 53.7 a | 17.1 a |
| Zn-EDTA | 41.7 b | 10.7 b | 61.6 a | 20.0 a |
| ZnO NPs | 40.7 b | 12.7 ab | 63.6 a | 22.0 a |
1 Means in the same column followed by the same letters were not significantly different (Tukey’s test, p ≤ 0.05). Data are on the basis of FW. FW, fresh weight; GAE, gallic acid equivalents; NZN, nitrazinc, containing Zn(NO3)2 and urea-ammonium nitrate fertiliser; QE, quercetin equivalents; TC, total carotenoids; TChl, total chlorophyll; TFl, total flavonoids; TP, total phenols; Zn-EDTA, zinc ethylene diamine-tetraacetic acid; ZnO NPs, zinc oxide nanoparticles; ZnSO4, zinc sulphate.