Mitigation of drought stress in lettuce (Lactuca sativa L.) through application of zinc-oxide nanoparticles and humic acid: evaluation of growth, physiological, and biochemical indicators
5 affiliations
- 1Al-Noor Center for Smart Agriculture Research and Sustainable Production, Alnoor University
- 2Department of Horticulture and Landscape,College of Agriculture and Forestry, University of Mosul
- 3Northern Technical University
- 4Ninevah University
- 5Department of Horticultural Sciences, Faculty of Agriculture & Natural Resources, Ardakan University
Abstract
Drought stress is one of the major abiotic constraints limiting the growth and productivity of lettuce (Lactuca sativa L.). This study aimed to evaluate the potential role of zinc oxide nanoparticles (ZnO NPs) and humic acid (HA) in mitigating adverse effects of drought stress on growth, physiological, and biochemical attributes of lettuce. A split factorial experiment was conducted based on a randomized complete block design (RCBD) with three replications, including three irrigation regimes (100, 75, and 50% of field capacity), three levels of ZnO NPs (0, 10, and 30 mg L⁻1), and three concentrations of HA (0-, 4-, and 6-mL L⁻1). The results revealed that drought stress significantly reduced growth parameters, photosynthetic pigments, relative water content, and leaf nitrogen, while it increased electrolyte leakage, proline accumulation, antioxidant enzyme activity, and secondary metabolites such as phenols and flavonoids. Application of humic acid, particularly at 4 mL L⁻1, markedly improved plant growth, enhanced water status, stabilized cell membranes, and promoted photosynthetic efficiency under both normal and water-deficit conditions. In contrast, ZnO nanoparticles at the applied concentrations showed limited or negative effects, possibly due to suboptimal dosage or unfavorable physiological responses under the tested conditions, and in some cases intensified stress responses. Application of 6- and 4-ml L-1 HA, respectively improved leaf area by 20% and 15% under 50% FC irrigation. Also, 4 mL L-1 HA caused a significant increase by 16% in the fresh weight of leaves under 50% FC irrigation and the increases by 25% and 13%, respectively in fresh and dry weights in the control plants. Inclusive, the findings demonstrate that humic acid acts as an effective biostimulant in alleviating drought stress and improving lettuce performance, whereas the application of ZnO nanoparticles requires careful optimization of dosage. Overall, 4 mL L-1 of HA potentially supports lettuce plants under irrigation deficit and reduces the adverse effects of drought. These results highlight the potential of sustainable inputs such as humic substances for enhancing crop resilience under water-limited conditions.
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BibTeX
@article{allela2026mitigation,
title = {{Mitigation of drought stress in lettuce (Lactuca sativa L.) through application of zinc-oxide nanoparticles and humic acid: evaluation of growth, physiological, and biochemical indicators}},
author = {Waleed B. M. Allela and Fathel F. R. Ibraheem and Amer M. A. Alramadan and Hussein J. M. AL-Bayati and Zainab Abdulaziz and Zainb. T. Faris and Aya Mohammed Ali and Mohammed. J. Mohammed and Majd M. Yaqoob and Heidar Meftahizade},
journal = {Scientific Reports},
year = {2026},
month = jul,
doi = {10.1038/s41598-026-63208-5},
url = {https://doi.org/10.1038/s41598-026-63208-5},
note = {CC BY},
}
RIS
TY - JOUR
TI - Mitigation of drought stress in lettuce (Lactuca sativa L.) through application of zinc-oxide nanoparticles and humic acid: evaluation of growth, physiological, and biochemical indicators
AU - Waleed B. M. Allela
AU - Fathel F. R. Ibraheem
AU - Amer M. A. Alramadan
AU - Hussein J. M. AL-Bayati
AU - Zainab Abdulaziz
AU - Zainb. T. Faris
AU - Aya Mohammed Ali
AU - Mohammed. J. Mohammed
AU - Majd M. Yaqoob
AU - Heidar Meftahizade
PY - 2026
DA - 2026/07/01
JO - Scientific Reports
DO - 10.1038/s41598-026-63208-5
UR - https://doi.org/10.1038/s41598-026-63208-5
AB - Drought stress is one of the major abiotic constraints limiting the growth and productivity of lettuce (Lactuca sativa L.). This study aimed to evaluate the potential role of zinc oxide nanoparticles (ZnO NPs) and humic acid (HA) in mitigating adverse effects of drought stress on growth, physiological, and biochemical attributes of lettuce. A split factorial experiment was conducted based on a randomized complete block design (RCBD) with three replications, including three irrigation regimes (100, 75, and 50% of field capacity), three levels of ZnO NPs (0, 10, and 30 mg L⁻1), and three concentrations of HA (0-, 4-, and 6-mL L⁻1). The results revealed that drought stress significantly reduced growth parameters, photosynthetic pigments, relative water content, and leaf nitrogen, while it increased electrolyte leakage, proline accumulation, antioxidant enzyme activity, and secondary metabolites such as phenols and flavonoids. Application of humic acid, particularly at 4 mL L⁻1, markedly improved plant growth, enhanced water status, stabilized cell membranes, and promoted photosynthetic efficiency under both normal and water-deficit conditions. In contrast, ZnO nanoparticles at the applied concentrations showed limited or negative effects, possibly due to suboptimal dosage or unfavorable physiological responses under the tested conditions, and in some cases intensified stress responses. Application of 6- and 4-ml L-1 HA, respectively improved leaf area by 20% and 15% under 50% FC irrigation. Also, 4 mL L-1 HA caused a significant increase by 16% in the fresh weight of leaves under 50% FC irrigation and the increases by 25% and 13%, respectively in fresh and dry weights in the control plants. Inclusive, the findings demonstrate that humic acid acts as an effective biostimulant in alleviating drought stress and improving lettuce performance, whereas the application of ZnO nanoparticles requires careful optimization of dosage. Overall, 4 mL L-1 of HA potentially supports lettuce plants under irrigation deficit and reduces the adverse effects of drought. These results highlight the potential of sustainable inputs such as humic substances for enhancing crop resilience under water-limited conditions.
SN - 2045-2322
ER -