Abstract
Soybean production is frequently limited by drought stress. While zinc oxide nanoparticles (ZnO NPs) have shown potential in enhancing plant stress tolerance, their efficacy and toxicity under drought conditions remain poorly understood, especially in a genotype-dependent context. This study applied drought stress to two soybean varieties with significantly different drought resistance (drought-tolerant Heinong 87, HN87, and drought-sensitive Hefeng 55, HF55). The effects of foliar spraying with zinc oxide nanoparticles at different concentrations (50, 100, 200, and 400 mg/L) and application frequencies (1–6 times) were tested. Low concentrations of ZnO NPs (≤ 200 mg/L) significantly alleviated drought stress, enhancing root volume by up to 32.0 % in the tolerant variety and restoring stomatal conductance by 24.6 % in the sensitive variety. However, high concentration (400 mg/L) or excessive spray application (>3 times) induced significant toxicity, inhibiting root growth and reducing leaf fresh weight by more than 30.0 %. Low-dose ZnO NPs enhanced photosynthetic efficiency by 14.7–49.1 %, while high doses reduced it by 45.4–66.3 %, highlighting concentration-dependent effects. Regression modeling quantitatively defined the optimal spray frequency, with growth maxima occurring at or before 3 applications. Based on this model-derived optimum and the genotype-specific response patterns, we propose a precision application strategy: for drought-tolerant varieties, the model supports 100–200 mg/L sprayed up to 3 times as optimal, whereas for sensitive varieties, the data indicate a lower threshold of 50–100 mg/L is required to avoid toxicity. This study provides a theoretical basis and practical guidance for the safe application of nanomaterials in agriculture. • Nano-zinc oxide is an effective tool for the management of soybean drought stress. • Nano-zinc oxide has the dual effects of mitigation and toxicity. • A precise application strategy (50–200 mg/L and ≤3 applications) was proposed. • This strategy reduces phytotoxicity and environmental hazards linked to nano-zinc.
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Claims 10
Claim · model-written summary
Low ZnO NP concentrations alleviated drought stress in soybean.
- Taxon
- soybean
Glycine maxt0 - Treatment
- Low concentrations of ZnO NPs (≤ 200 mg/L)e0
- Outcome
- drought stresse0
- Direction
- alleviatede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Low concentrations of ZnO NPs (≤ 200 mg/L) significantly alleviated drought stress”
t0“soybean”
Claim · model-written summary
Low ZnO NP concentrations increased root volume by up to 32.0% in the tolerant variety.
- Taxon
- soybeanGlycine maxt0
- Material
- tolerant varietye0
- Treatment
- Low concentrations of ZnO NPs (≤ 200 mg/L)e1
- Outcome
- root volumee0
- Direction
- enhancinge0
- Value
- 32.0 %e0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“enhancing root volume by up to 32.0 % in the tolerant variety”
t0“soybean”
e1“Low concentrations of ZnO NPs (≤ 200 mg/L)”
Claim · model-written summary
Low ZnO NP concentrations restored stomatal conductance by 24.6% in the sensitive variety.
- Taxon
- soybeanGlycine maxt0
- Material
- sensitive varietye0
- Treatment
- Low concentrations of ZnO NPs (≤ 200 mg/L)e1
- Outcome
- stomatal conductancee0
- Direction
- restoringe0
- Value
- 24.6 %e0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“restoring stomatal conductance by 24.6 % in the sensitive variety”
t0“soybean”
e1“Low concentrations of ZnO NPs (≤ 200 mg/L)”
Claim · model-written summary
A 400 mg/L concentration or more than three sprays caused significant toxicity and inhibited root growth.
- Taxon
- soybeanGlycine maxt0
- Treatment
- high concentration (400 mg/L) or excessive spray application (>3 times)e0
- Outcome
- root growthe0
- Direction
- inhibitinge0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“high concentration (400 mg/L) or excessive spray application (>3 times) induced significant toxicity, inhibiting root growth”
t0“soybean”
Claim · model-written summary
A 400 mg/L concentration or more than three sprays reduced leaf fresh weight by more than 30.0%.
- Taxon
- soybeanGlycine maxt0
- Treatment
- high concentration (400 mg/L) or excessive spray application (>3 times)e0
- Outcome
- leaf fresh weighte0
- Direction
- reducinge0
- Value
- 30.0 %e0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“high concentration (400 mg/L) or excessive spray application (>3 times) induced significant toxicity, inhibiting root growth and reducing leaf fresh weight by more than 30.0 %”
t0“soybean”
Claim · model-written summary
Low-dose ZnO NPs enhanced photosynthetic efficiency by 14.7–49.1%.
- Taxon
- soybeanGlycine maxt0
- Treatment
- Low-dose ZnO NPse0
- Outcome
- photosynthetic efficiencye0
- Direction
- enhancede0
- Value
- 14.7–49.1 %e0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Low-dose ZnO NPs enhanced photosynthetic efficiency by 14.7–49.1 %”
t0“soybean”
Claim · model-written summary
High doses reduced photosynthetic efficiency by 45.4–66.3%.
- Taxon
- soybeanGlycine maxt0
- Treatment
- high dosese0
- Outcome
- photosynthetic efficiencye1
- Direction
- reducede0
- Value
- 45.4–66.3 %e0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“high doses reduced it by 45.4–66.3 %”
t0“soybean”
e1“photosynthetic efficiency by 14.7–49.1 %”
Claim · model-written summary
Regression modeling placed growth maxima at or before three applications.
- Taxon
- soybeanGlycine maxt0
- Outcome
- growth maximae0
- Direction
- maximae0
- Value
- 3 applicationse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Regression modeling quantitatively defined the optimal spray frequency, with growth maxima occurring at or before 3 applications”
t0“soybean”
Claim · model-written summary
The authors recommend 100–200 mg/L up to three times for drought-tolerant varieties.
- Taxon
- soybeanGlycine maxt0
- Material
- drought-tolerant varietiese0
- Outcome
- 100–200 mg/L sprayed up to 3 times as optimale0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“for drought-tolerant varieties, the model supports 100–200 mg/L sprayed up to 3 times as optimal”
t0“soybean”
Claim · model-written summary
The authors indicate 50–100 mg/L for sensitive varieties to avoid toxicity.
- Taxon
- soybeanGlycine maxt0
- Material
- sensitive varietiese0
- Outcome
- lower threshold of 50–100 mg/L is required to avoid toxicitye0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“for sensitive varieties, the data indicate a lower threshold of 50–100 mg/L is required to avoid toxicity”
t0“soybean”
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