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Tolerance to sodium chloride in lettuce enhanced by potassium nitrate Cover

Tolerance to sodium chloride in lettuce enhanced by potassium nitrate

Environmental Protection and Natural Resources
Volume 36 (2025): Issue 4 (December 2025)
By: Mykola Kharytonov,  Alla Samarska,  Oleksandr Kovrov and  Hermann Heilmeier  
Open Access
|Mar 2026
Figures & tables

Figures & Tables

Figure 1.

Fresh weight of leavesNitrate Level A: 20 mM, Nitrate Level B: 40 mM; Salt Level A: 100 mM, Salt Level B: 200 mM;Interaction 1 Level A – Salt 100 mM + Nitrate 20 mM, Interaction 1 Level B – Salt 100 mM + Nitrate 40 mM;Interaction 2 Level A – Salt 200 mM + Nitrate 20 mM, Interaction 2 Level B – Salt 200 mM + Nitrate 40 mMANOVA: Treatment:Concentration – p < 0.001. Values are expressed as means ± standard error (n = 5). The control mean is shown by the blue line, and the standard error by the blue dotted lines.

Figure 2.

Electrical conductivity of leavesNitrate Level A – 20 mM, Nitrate Level B – 40 mM; Salt Level A – 100 mM, Salt Level B – 200 mM;Interaction 1 Level A – Salt 100 mM + Nitrate 20 mM, Interaction 1 Level B – Salt 100 mM + Nitrate 40 mM;Interaction 2 Level A – Salt 200 mM + Nitrate 20 mM, Interaction 2 Level B – Salt 200 mM + Nitrate 40 mMANOVA: Treatment:Concentration – p < 0.05. Values are expressed as means ± standard error (n = 5). The control mean is shown by the blue line, the standard error by the blue dotted lines.

Figure 3.

MDA content (nmol/g FW) in lettuce leaves depending on treatment and concentrationNitrate Level A – 20 mM, Nitrate Level B – 40 mM, Salt Level A – 100 mM, Salt Level B – 200 mM;Interaction 1 Level A – Salt 100 mM + Nitrate 20 mM, Interaction 1 Level B – Salt 100 mM + Nitrate 40 mM;Interaction 2 Level A – Salt 200 mM + Nitrate 20 mM, Interaction 2 Level B – Salt 200 mM + Nitrate 40 mMANOVA: Treatment:Concentration – p < 0.001. Values are expressed as means ± standard error (n = 5). The control mean is shown by the blue line, the standard error by the blue dotted lines.

Figure 4.

Proline content (μg/g FW) in lettuce leaves depending on treatment and concentrationNitrate Level A – 20 mM, Nitrate Level B – 40 mM, Salt Level A – 100 mM, Salt Level B – 200 mM;Interaction 1 Level A – Salt 100 mM + Nitrate 20 mM, Interaction 1 Level B – Salt 100 mM + Nitrate 40 mM;Interaction 2 Level A – Salt 200 mM + Nitrate 20 mM, Interaction 2 Level B – Salt 200 mM + Nitrate 40 mMANOVA: Treatment:Concentration – p < 0.001. Values are expressed as means ± standard error (n = 5). The control mean is shown by the blue line, the standard error by the blue dotted lines.

Figure 5.

Chlorophyll a content in lettuce leaves depending on treatment and concentrationANOVA: Treatment:Concentration – p < 0.001. Values are expressed as means ± standard error (n=5). The control mean is shown by the blue line, the standard error by the blue dotted lines.

Figure 6.

Chlorophyll b content in lettuce leaves depending on treatment and concentrationANOVA: Treatment: Concentration – p < 0.001. Values are expressed as means ± standard error (n=5). The control mean is shown by the blue line, the standard error by the blue dotted lines.

Figure 7.

Carotenoid content in lettuce leaves depending on treatment and concentrationANOVA: Treatment:Concentration; p < 0.001. Values are expressed as means ± standard error (n = 5). The control mean is shown by the blue line, the standard error by the blue dotted lines.

Figure 8.

The ratio of total chlorophyll to carotenoids depending on treatment and concentrationANOVA: Treatment: Concentration – p < 0.001. Values are expressed as means ± standard error (n=5). The control mean is shown with the blue line, and the standard error with blue dotted lines.

Figure 9.

Pearson's correlation matrix with p-values for MDA, proline, photosynthetic pigments, EC and FW

Electrical conductivity (EC) of soil (mean ± se, n = 5)

TreatmentConcentrationEC soil mean ± se, μS/cm
1Interaction 2Level B1331 ± 18.6a
2Interaction 2Level A1167 ± 27.2b
3Interaction 1Level B1002 ± 14.9c
4SaltLevel B959 ± 4.17c
5Interaction 1Level A855 ± 7.40d
6SaltLevel A603 ± 13.3e
7NitrateLevel B316 ± 7.02f
8NitrateLevel A166 ± 5.22g
9ControlWater27.2 ± 1.39

Chl a / Chl b ratio depending on two factors: treatment and concentration

TreatmentConcentrationRatio of Chl a / Chl b mean ± se
1SaltLevel A5.21 ± 0.350a
2SaltLevel B5.03 ± 0.361ab
3NitrateLevel B4.38 ± 0.139abc
4NitrateLevel A4.18 ± 0.278abc
5Interaction 1Level A4.11 ± 0.224abc
6Interaction 2Level B4.08 ± 0.196abc
7Interaction 2Level A3.96 ± 0.331bc
8Interaction 1Level B3.16 ± 0.185c
DOI: https://doi.org/10.2478/oszn-2025-0023 | Journal eISSN: 2353-8589 | Journal ISSN: 1230-7831
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Language: English
Page range: 28 - 40
Published on: Mar 17, 2026
Published by: National Research Institute, Institute of Environmental Protection
In partnership with: Paradigm Publishing Services
Publication frequency: 4 issues per year
Keywords:
lettuce,
NaCl salt stress,
potassium nitrate,
malondialdehyde,
proline,
pigments
Related subjects:
Life sciences,
Ecology

© 2026 Mykola Kharytonov, Alla Samarska, Oleksandr Kovrov, Hermann Heilmeier, published by National Research Institute, Institute of Environmental Protection
This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

Volume 36 (2025): Issue 4 (December 2025)
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