Mitigating Salt Toxicity in Tomato Plants via Foliar Silver Nanoparticle Application

Mohammed Othman Ahmed

doi:10.24017/

Authors

Mohammed Othman Ahmed Department of Horticulture, College of Agricultural Engineering Sciences, University of Raparin, Sulaymaniyah, Iraq.| Department of Plant Physiology and Plant Ecology, Institute of Agronomy, Hungarian University of Agriculture and Life Sciences, Budapest, Hungary. Author https://orcid.org/0000-0002-9170-1931

DOI:

https://doi.org/10.24017/

Keywords:

Salinity stress, Tomato cultivars, Silver nanoparticles, Catalase activity, Plants under stress

Abstract

Soil salinity severely reduces crop productivity by inducing osmotic and oxidative stresses. This study examines the potential of foliar silver nanoparticle (AgNP) application to mitigate salinity stress in tomato (Solanum lycopersicum) seedlings. Two local cultivars, Patatayi and Sewa, were exposed to 200 mM sodium chloride (NaCl) for 4 weeks, with or without 50 ppm AgNPs, to assess morphological, photosynthetic and biochemical responses. Under saline conditions, growth was severely compromised, with total plant height reduced by 24.98% and total chlorophyll levels decreased by 41% in Patatayi and by 50% in Sewa relative to control plants. However, exogenous AgNP application under saline conditions markedly alleviated these adverse effects. Compared with NaCl-stressed plants, co-application of NaCl and AgNPs increased overall plant height by 12.4%, total chlorophyll by 25.7%, free proline by 12.6% and catalase (CAT) activity by 53.6%. The ability of AgNPs to mitigate stress was strictly dependent on the cultivar, Patatayi showed strong recovery in vegetative growth (plant height +12.8%, leaf area +17.1%, and leaf number +21.3%) and good photochemical stability (Fv/Fm +18.9%, from 0.619 to 0.736), whereas Sewa mainly relied on enzymatic antioxidants such as CAT (+50%). Multivariate principle componenet analysis (73.8% cumulative variance) separated the salt stressed from the non-stressed plants along PC1 (54.1%) and the cultivars along PC2 (19.6%). The foliar AgNPs shifted the salt stressed Patatayi towards the control profile and Sewa clustered with the highest CAT activity. Furthermore, Pearson correlation analysis confirmed strong positive associations between photosynthetic traits (r = 0.72, p < 0.001), which correlated negatively with malondialdehyde (MDA; r = -0.78, p < 0.001), whereas positive correlations between MDA, free proline (r = 0.66, p < 0.001), and CAT (r = 0.41, p < 0.05) underscored a proportional cytoprotective response to oxidative stress. In conclusion, foliar application of AgNPs is a practical, genotype-specific method for relieving salt toxicity in tomatoes by improving osmoprotection and scavenging reactive oxygen species.

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