Acta agriculturae Slovenica, 121/4, 1–11, Ljubljana 2025 doi:10.14720/aas.2025.121.4.23310 Original research article / izvirni znanstveni članek Modulation of yield and physiological attributes of cumin (Cuminum cyminum L.) by silicon dioxide nanoparticles under varying drought stresses Mohammad Esmaeil AMERI BAFQI 1, Heshmat OMIDI 1, 2, Amir Mohammad NAJI 1, and Amir BOSTANI 1 Received August 17, 2025, accepted November 19, 2025 Delo je prispelo 17. avgust 2025, sprejeto 19. november 2025 1 Department of Agronomy and Plant Breeding, College of Agriculture, Shahed University, Tehran, Iran 2 Corresponding author e-mail: omidi@shahed.ac.ir Modulation of yield and physiological attributes of cumin (Cuminum cyminum L.) by silicon dioxide nanoparticles un- der varying drought stresses Abstract: Water scarcity, exacerbated by climate change and population growth, threatens sustainable agriculture, par- ticularly in arid regions. This study investigated the potential of silicon dioxide nanoparticles (nSi) to mitigate drought stress in cumin (Cuminum cyminum L.). A split-plot experiment, ar- ranged in a randomized complete block design with three rep- lications, was conducted over two cropping seasons in Bafgh, Iran. Drought stress was applied as the main factor at four levels (80 %, 60 %, 40 %, and 20 % of field capacity, FC), while sub- plots contained four nSi concentrations (0, 2, 4, and 6 mM). Re- sults showed that severe drought stress (20 % FC) significantly decreased seed yield, essential oil yield, and total chlorophyll, while increasing peroxidase activity and malondialdehyde lev- els. Application of 4 mM nSi significantly improved seed yield and essential oil yield and preserved total chlorophyll, and sus- tained peroxidase activity, leading to lower malondialdehyde levels. In contrast, 6 mM nSi did not improve seed yield and essential oil yield and, in fact, worsened its effects. Overall, 4 mM nSi can enhance cumin’s resilience and productivity under drought, while higher concentrations should be avoided. Key words: seed yield, essential oil yield, malondialde- hyde, eroxidase activity Modulacija pridelka in fizioloških lastnosti rimske kumine (Cuminum cyminum L.) z nanodelci silicijevega dioksida pri različnih sušnih stresih Izvleček: Pomanjkanje vode, ki ga poslabšujejo podnebne spremembe in rast prebivalstva, ogroža trajnostno kmetijstvo, zlasti v sušnih regijah. Ta raziskava je preučevala potencial nanodelcev silicijevega dioksida (nSi) za ublažitev sušnega stre- sa pri rimski kumini (Cuminum cyminum L.). Poskus z deljen- kami, zasnovan kot popolni naključni poskus s tremi ponovit- vami, je bil izveden v dveh rastnih sezonah v Bafghu v Iranu. Sušni stres je bil uporabljen kot glavni dejavnik na štirih ravneh (80 %, 60 %, 40 % in 20 % poljske kapacitete, FC), medtem ko so podploskve vsebovale štiri koncentracije obravnavanja z nSi (0, 2, 4 in 6 mM). Rezultati so pokazali, da je huda suša (20 % FC) občutno zmanjšala pridelek semen, pridelek eteričnega olja in vsebnost celokupnega klorofila, hkrati pa povečala aktivnost peroksidaze in ravni malondialdehida. Uporaba 4 mM nSi je znatno izboljšala pridelek semen in eteričnega olja ter ohranila skupni klorofil in trajno aktivnost peroksidaze, kar je vodilo do nižjih ravni malondialdehida. Nasprotno pa uporaba 6 mM nSi ni izboljšala pridelka semen in eteričnega olja in je dejansko poslabšala njegove učinke. Na splošno lahko 4 mM nSi poveča odpornost in produktivnost rimske kumine v suši, medtem ko se je treba večjim koncentracijam izogibati. Ključne besede: pridelek semena, pridelek eteričnega olja, malondialdehid, aktivnost peroksidaze Acta agriculturae Slovenica, 121/4 – 20252 M. E. AMERI BAFQI et al. 1 INTRODUCTION Cumin (Cuminum cyminum L.), an aromatic herb from the Apiaceae family, has been used globally in medicine and cooking for centuries (Sowbhagya, 2013). Beyond its culinary uses, cumin traditionally alleviates ailments like toothache, diarrhea, epilepsy (Johri, 2011), jaundice, and indigestion (Rudra Pratap, Gangadharappa, & Mruthunjaya, 2017), attributed to antioxidants such as anthocyanins, flavonoids, and phenolic compounds (Alinian & Razmjoo, 2014). Cumin is mainly cultivated in Asia, the Middle East, and North Africa, with India and Iran as leading pro- ducers and exporters (Noori, Moosavi, Seghatolesla- mi, & Fazeli Rostampour, 2022). Abdollah (2009) research in Torbat-jam, Iran, demonstrated that cumin production under irrigated conditions (513.40 kg ha-1) significantly exceeded that of rain-fed conditions (480.34 kg ha-1), underscoring the critical role of water availability in cumin yield and sustainable agriculture. However, increasing water scarcity, exacerbated by climate change and popula- tion growth, necessitates improved water management in arid and semi-arid regions. Silicon, the second most abundant element in soil (Sharma et al., 2023), enhances plant growth, devel- opment, and stress tolerance despite not being essen- tial. It improves disease and pest resistance, reduces pesticide use (Samal, Bhoi, Mahanta, & Komal, 2024), alleviates nutrient imbalance, and boosts physiologi- cal functions (Frew, Weston, Reynolds, & Gurr, 2018; Kovács, Kutasy, & Csajbók, 2022). Si also protects against metal toxicity, oxidative stress, and phenolic browning (Leroy, de Tombeur, Walgraffe, Cornélis, & Verheggen, 2019). Foliar Si application benefits plants facing salinity (Mohammadi, Abdollahi-Bastam, Aghaee, & Ghorbanpour, 2024; Teimoori, Ghobadi, & Kahrizi, 2023), drought (Sutulienė et al., 2022), floods (Chu et al., 2018), heat (Xiao, Li, & Jeong, 2022), cold (Alhasnawi & Al-Bayati, 2023), and biological stresses, activating stress-responsive genes and enhancing tol- erance pathways (Mir et al., 2022). While bulk silicon can be phytotoxic, nano-sili- con (nSi) is eco-friendly and enhances crop tolerance to both abiotic and biotic stresses (Helaly, El-Hoseiny, El-Sheery, Rastogi, & Kalaji, 2017). Applying nSi is rec- ommended for improving drought tolerance by reduc- ing reactive oxygen species (ROS) in barley (Ghorban- pour, Mohammadi, & Kariman, 2020), wheat (Ahmadi Nouraldinvand, Seyed Sharifi, Siadat, & Khalilzadeh, 2023), faba beans (Desoky et al., 2021), and cherry to- matoes (Haghighi & Pessarakli, 2013). Silicon allevi- ates abiotic stress by activating plant antioxidants, im- mobilizing toxic metal ions, and sequestering metals within the plant (Verma et al., 2022). Foliar and soil applications of fertilizers elicit dis- tinct plant responses. Foliar application, which rapidly delivers nutrients to leaves, boosts plant protection and yield, especially under stress like drought or salin- ity (Deng et al., 2022). Foliar spraying provides quick- er gains in plant height and growth compared to soil methods and is also more economical due to reduced resource use (Alim et al., 2023). The effect of foliar nSi application on cumin (Cuminum cyminum L.) remains understudied. Exist- ing research has either focused on black cumin (Ni- gella sativa L.) or has been conducted in controlled environments. This study investigated foliar nSi appli- cation to alleviate water stress in cumin grown under the semi-arid and arid conditions of central Iran, thus addressing a significant research gap. 2 MATERIALS AND METHODS 2.1 EXPERIMENTAL DESIGN, LAND PREPARA- TION, AND CROP MANAGEMENT A field study was carried out in Bafq city, Yazd province, Iran (31° 58’ N 55° 04’ E) during two crop- ping seasons (2022-23) to assess the impacts of foliar application of nSi and drought stress on the growth, yield, and physiological responses of cumin (Cumi- num cyminum L.). Meteorological data during the 2022 and 2023 planting seasons at experimental site, are presented in Table 1 (https://www.irimo.ir). The experiment was laid out as a split-plot design with three replications. Drought stress was applied at four levels (80, 60, 40, and 20 % of field capacity) in the main plots to represent varying water availability, while four levels of nSi foliar application (0, 2, 4, and 6 mM) were randomly assigned to the sub-plots (Fig. 1). In each cropping season, the process of land prepara- tion began in the autumn with deep plowing, reaching depths of up to 30 cm, for breaking up soil compac- tion and enhancing drainage. Subsequently, initial leveling was performed. Following this, assessments of soil texture and nutrient content were conducted. The land remained undisturbed until the spring, when fa- vorable conditions permitted further land preparation activities, including the use of a disc harrow and final leveling, to establish a uniform planting bed following the design plan. Acta agriculturae Slovenica, 121/4 – 2025 3 Modulation of yield and physiological attributes of cumin ... by silicon dioxide nanoparticles under varying drought stresses 2.2 FOLIAR NSI AND DROUGHT TREATMENT Foliar spray with nanoparticles of silicon dioxide (nSi = 20–30 nm, Iranian Pioneers of Nanomaterials Co., Vakilabad, Mashhad, Iran) supplemented with Jonobgan ionic foliar spray soap as a surfactant (Kerman Zamin Co., Kerman, Iran), was applied two times at two growth stages: 1) after the six-leaf stage, and 2) before flower- ing. Control plants were also sprayed at the same times with distilled water, supplemented with surfactant soap to eliminate any treatment-related effects from the sur- factant. Validation of nanoparticle size specifications provided by the manufacturer was performed using transmission electron microscopy, which confirmed a precise particle diameter of approximately 30 nm. Drought stress was induced post the six-leaf stage, and after plant establishment. Soil moisture levels were monitored using the pressure plate method, which in- volves preparing soil samples, saturating them under specific pressures, and drying them to measure soil mois- ture percentage. After calculating the moisture content of soil samples at field capacity and permanent wilting point (PWP) and determining the apparent specific mass of the soil, the volumetric moisture at FC and PWP points was calculated for each drought level. 2.3 SAMPLING AND TRAIT MEASUREMENT 2.3.1 Physiological and biochemical traits In each cropping season, one week after the second foliar spray, samples were collected from the plots and frozen for later analysis. 2.3.2 Plant measurements at harvest After harvest, ten plants were randomly selected from each plot to measure the following traits: seed yield (SY, kg. ha-1), plant height (PH, cm), and number of um- bels per plant (NU), number of seeds per umbel (NS), and thousand-seed mass (TSM, g). 2.3.3 Seed and essential oil yield Seeds were sown in five-row plots (2 m long, 30 cm row spacing) with a 1 m buffer zone. At harvest, samples were taken from each plot to measure seed yield. Samples were air-dried, weighed, and adjusted to standard units (kg ha-1). Seeds were crushed into a powder, and essential oils Cropping season AT (°C) AR (mm) ARH (%) Eva (mm. day-1) AST (°C) 2022 February 12.83 0.00 36.16 0.00 3.22 March 16.64 0.60 41.62 1.80 7.84 April 21.33 0.10 23.37 8.57 11.07 May 26.39 0.12 20.19 12.50 14.77 June 31.85 0.07 19.72 14.98 20.48 2023 February 17.63 0.00 27.42 5.36 7.22 March 21.47 0.09 24.13 7.58 10.90 April 25.06 0.10 18.94 10.21 14.13 May 31.36 0.00 13.52 12.10 18.29 June 37.62 0.00 12.93 15.72 24.63 Table 1: Meteorological data (obtained from Iran’s Meteorological Organization’s official website, https://www.irimo.ir) during the 2022 and 2023 cumin (Cuminum cyminum L.) planting seasons at the Bafq experimental site, Yazd provinces, Iran. AT: Average temperature, AR: Average rainfall, ARH: Average relative humidity, Eva: Evaporation, AST: Average soil temperature. Figure 1: The experimental schematic depicting the foliar ap- plication of varying concentrations of silicon dioxide nanopar- ticles on cumin (Cuminum cyminum L.) plants exposed to dif- ferent drought levels. Acta agriculturae Slovenica, 121/4 – 20254 M. E. AMERI BAFQI et al. were extracted from each sample via hydro distillation using a Clevenger apparatus for 2 hours. Extracts were dried with sodium sulfate, and essential oil yield was cal- culated as the product of seed yield and essential oil con- tent and reported as kg ha-1. 2.3.4 Leaf analyses The content of chlorophyll (TChl) was determined following the method of Lichtenthaler and Wellburn (1985). Malondialdehyde (MDA) content in leaf tissue was quantified by the thiobarbituric acid (TBA) assay accord- ing to Senthilkumar, Amaresan, and Sankaranarayanan (2021). Briefly, ~0.1 g of leaf tissue was homogenized in 1 ml ice-cold 0.1% trichloroacetic acid (TCA) and cen- trifuged at 12,000 g for 10 min at 4 °C. The supernatant (0.5 ml) was mixed with 0.5 ml of 0.5 % TBA in 20 % TCA and incubated at 95 °C for 30 min, then cooled on ice. Absorbance was read at 532 nm and corrected for non-specific absorbance at 600 nm. Malondialdehyde content was calculated using the extinction coefficient and expressed as nmol malondialdehyde per mg protein (protein quantified in the same extract by the Bradford assay). Peroxidase (POD) enzyme activity was measured following the method outlined by Maehly (1954). This method involved the combination of 50 μl of leaf sample extract with 3 ml of 1.0 M potassium phosphate buffer solution and 50 μl of guaiacol solution. Following this, 50 μl of 3 % hydrogen peroxide was added, and absorbance changes were recorded at 436 nm using a spectropho- tometer at intervals ranging from 0 to 3 minutes, with measurements taken every 15 seconds. 2.4 STATISTICAL ANALYSIS Statistical analyses were conducted using SAS soft- ware version 9.1 (SAS, 2003), assuming fixed treatment effects of drought stress and foliar nSi, while the cropping season was considered a random effect. Graphs were cre- ated in Microsoft Excel 2019 software. The analysis of variance followed the below model Gomez and Gomez (2009). Mean differences between treatments were as- sessed using Duncan’s test. 3 RESULTS The homogeneity of experimental error variances was assessed before the combined analysis of variance. The combined analysis of variance revealed a significant triple interaction effect of year, drought stress, and foliar application of nSi for all traits studied (Table 2). When the interaction term is significant interpretation of the main effects from the analysis of variance is impossible or at best unreliable (Dunne, 2010). Therefore, this research Source DF SY EOY PH NU NS TSM TChl MDA POD Y 1 18477.89 11.8 729.65 41.04 365.66 9.38 562.54 0.08 97.31 Y(R) 4 2476.95 4.56 0.87 9.36 4.83 0.03 0.56 0.2 0.33 D 3 1469608.63 ** 559.5 ** 743.77 ns 150.05 ns 749.33 ** 3.99 ns 212.26 ns 25.44 ns 488.65 ns Y × D 3 36072.09 ** 5.19 ns 87.58 ** 31.08 ** 9.78 ns 0.84 * 35.26 ** 2.82 ** 94.83 ** Error 1 12 1540.48 2.13 1.1 4.7 4.49 0.17 0.3 0.18 0.73 nSi 3 103948.19 * 31.2 ns 100.44 ns 23.09 ns 24.02 * 1.54 ns 140.19 ns 9.07 * 52.57 ns Y × Si 3 5596.78 ns 4.35 * 50.05 ** 10.91 ** 1.69 ns 0.3 ns 39.62 ** 0.52 ns 26.99 ** D × Si 9 24554.88 * 36.01 * 24.35 ns 53.66 ns 16.03 ns 0.52 ns 23.63 * 4.42 ns 17.3 ns Y × D × Si 9 7084.4 * 10.69 ** 41.03 ** 24.61 ** 7.2 * 0.56 ** 5.11 ** 3.2 ** 6.27 ** Error 2 48 2573.1 ns 1.16 2.42 1.57 2.76 0.12 0.6 0.21 0.78 MPCV % 10.18 22.87 4.42 15.06 10.64 17.28 3.26 9.08 12.15 SPCV % 13.15 16.87 6.54 8.71 8.35 14.46 4.58 9.94 12.61 Table 2: Combined analysis of variance for drought stress and foliar application of silicon dioxide nanoparticles effects on cumin traits across two cropping seasons. *, and ** indicate significant at the 0.05 and 0.01 levels of probability, respectively. Y: Effect of Year; R: Replication; D: Effect of Drought; nSi: Effect of Silicon dioxide nanoparticles; CV: coefficient of variations. PH: Plant height; NU: Number of umbels per plant; NS: Number of seeds per umbel; TSM: Thousand seed mass; SY: Seed yield; EOY: Essential oil yield; TChl: Total chlorophyll content; MDA: Malondialdehyde content; POD: Peroxidase enzyme activity. Acta agriculturae Slovenica, 121/4 – 2025 5 Modulation of yield and physiological attributes of cumin ... by silicon dioxide nanoparticles under varying drought stresses focuses solely on the described triple interaction effect in the presentation and interpretation of the results. 3.1 SEED YIELD Seed yield response to varying nano-silicon concen- trations was non-linear under different drought stress levels. Average seed yield in 2022 was approximately 7 % lower than in 2023. In the absence of foliar nSi, mild, moderate, and severe drought stresses reduced seed yield in 2022 by 7 %, 67 %, and 81 %, respectively, compared to the control. Similar reductions were observed in 2023 (Fig. 2). Under non-stressed conditions (80 % FC) in 2023, seed yield initially increased significantly with rising nSi concentration, peaking at 4 mM before decreasing at 6 mM. In 2023, 4 mM nSi under mild stress resulted in the optimal yield increase, whereas 6 mM nSi decreased yield. Under moderate stress, nSi mitigated negative im- pacts on seed yield. In 2023, 2 mM nSi boosted yield by 79 %, and in 2022, 4 mM nSi increased it by 67 %. Under severe stress, 4 mM nSi increased yield by 52 % in 2022 and 29 % in 2023, although these increases were not sta- tistically significant (Fig. 2). 3.2 ESSENTIAL OIL YIELD Under non-stressed conditions in 2023, 2 mM na- no-silicon produced the highest essential oil yield, 81 % greater than the control (Fig. 3). Foliar nSi application also mitigated drought stress, increasing essential oil yield under mild stress by 3.4-fold (2022) and 2.1-fold (2023) with 2 mM nSi, as compared with the control. Under moderate stress, 4 mM nSi in- creased essential oil yield by 2.6-fold in 2022, and 6 mM nSi increased it by 2.8-fold in 2023, relative to the control (Fig. 3). 3.3 YIELD COMPONENTS In 2023 without drought, plant height ranged from 27.74 cm (0 mM nSi) to 46.36 cm (4 mM nSi), but de- creased to 33.12 cm at 6 mM nSi. Under mild drought, 4 mM nSi significantly increased plant height compared to the control in both years. Under moderate drought, 6 mM nSi increased plant height in 2022, while 4 mM nSi increased plant height in 2023, both relative to the control. Under severe drought, nSi did not significantly enhance plant height in 2022, but in 2023, 6 mM nSi increased plant height by 40 % compared to the control (Fig. 4). In 2023, the number of umbels per plant ranged from 15.3 to 25.5 with 0-2 mM nSi, but decreased to 15.9-22.4 with 4-6 mM. Under mild drought, 2 mM nSi increased this trait compared to the control in both years. Likewise, under moderate drought, 6 mM nSi improved the number of umbels per plant in 2022 (47 %) and 2023 (74 %). During severe drought in 2023, nSi did not en- hance this trait, but in 2022, 4 mM nSi increased it by 29 % (Fig. 4). In 2023 without drought, the number of seeds per umbel ranged from 26.5 to 31.2 under 0–4 mM nSi, de- creasing to 27.1 at 6 mM. With mild stress, 6 mM nSi increased seed number in 2023 but not in 2022. Under moderate stress, nSi had no effect in 2023, but 6 mM nSi increased it in 2022. During severe drought, 4 mM nSi resulted in the highest seed number, with no significant difference from 2–6 mM. The maximum seed number was observed in 2023 under normal conditions with 4 mM nSi (Fig. 4). Figure 3: Comparison of average essential oil yield of cumin (Cuminum cyminum L.) influenced by Nano-Silica foliar appli- cation and different drought stress levels. Differences between columns with a common letter are not significant according to Duncan’s test (α = 0.05). Figure 2: Comparison of average seed yield of cumin (Cumi- num cyminum L.) under Nano-Silica foliar application and dif- ferent drought stress levels. Differences between columns with a common letter are not significant according to Duncan’s test (α = 0.05). Acta agriculturae Slovenica, 121/4 – 20256 M. E. AMERI BAFQI et al. In 2023, drought reduced thousand-seed mass re- gardless of nSi treatment, while no reduction occurred in 2022. Without drought, nSi increased thousand-seed mass in both years. 4 mM nSi significantly increased 1000-grain mass compared to the control, but 6 mM nSi provided no further increase. Under mild stress, 2 mM nSi improved thousand-seed mass. Under moderate stress, nSi had no effect in 2022, but in 2023, 4 mM nSi increased thousand-grain mass by 68 %. During severe drought, nSi had no effect in 2022, but in 2023, 4 mM nSi increased 1000-grain mass by 77 %. 3.4 BIOCHEMICAL CHARACTERISTICS In 2023, 4 mM nSi significantly increased total chlorophyll content compared to the control, but 6 mM nSi offered no additional benefit. Without drought in 2023, 4 mM nSi significantly increased chlorophyll con- tent, while 6 mM nSi slightly decreased it. Under mild and moderate stress, 4 mM nSi significantly improved chlorophyll content compared to the control. Under severe drought, 2 mM nSi increased the trait by 26 % in 2022, while 4 mM nSi more than doubled it in 2023 (Fig. 5). Under normal irrigation, 6 mM nSi increased malondialdehyde, suggesting stress. However, under mild stress, both 4 and 6 mM nSi reduced malondial- dehyde in 2022. In 2023, 4 mM nSi also resulted in the lowest malondialdehyde, though not significantly lower than the control. Overall, 4 mM nSi significantly de- creased malondialdehyde compared to the control un- der both mild and severe stress (Fig. 5). In 2022, 6 mM nSi increased peroxidase activity under non-drought and mild stress, but not in 2023. Under moderate stress, 2 and 6 mM nSi resulted in the highest peroxidase activity in 2022; in 2023, only 6 mM nSi significantly increased it compared to the control. Under severe drought, 2 mM nSi enhanced peroxidase activity in 2022, while 2 and 4 mM nSi increased it in 2023 (Fig. 5). Figure 4: Average seed yield component traits in cumin (Cuminum cyminum L.) under nano silica foliar application and different drought stress levels during the 2022-2023 cropping seasons. Differences between means sharing a common letter are not significant according to Duncan’s test (α = 0.05). Acta agriculturae Slovenica, 121/4 – 2025 7 Modulation of yield and physiological attributes of cumin ... by silicon dioxide nanoparticles under varying drought stresses 4 DISCUSSION 4.1 EFFECTS OF SILICON NANOPARTICLES AND DROUGHT ON YIELD AND YIELD-RELATED TRAITS Cumin seed yield was lower in 2022 than in 2023. Lower soil and air temperatures in 2022 likely impacted cumin reproductive mechanisms by affecting key physi- ological processes like photosynthesis and respiration, crucial for flowering and reproductive development, especially the transition from vegetative to reproduc- tive stages (Valdés & Ehrlén, 2022). Conversely, higher rainfall in 2022 compared to 2023 may have reduced the effectiveness of nano-silica application due to foliar washout (Fageria, Filho, Moreira, & Guimarães, 2009). Regression analysis indicated that cumin seed yield was primarily influenced by traits thousand-seed mass and the number of seeds per umbel, while the number of umbels per plant had no significant effect, suggesting drought stress reduces cumin yield mainly through deg- radation of thousand-seed mass and the number of seeds per umbel. These results confirm that drought stress negatively affects cumin yield and related traits, consistent with pre- vious studies. Safari, Mahdi Mortazavian, Sadat-Noori, and Foghi (2015) reported a 34 % seed yield reduction under drought. This study aligns with Timachi, Armin, Jamimoeini, and Abhari (2023) and Salajegheh, Yavarza- deh , Payandeh, and Akbarian (2021), who showed that water deficit reduces the number of umbels per plant, number of seeds per umbel, thousand seed mass, seed yield, and essential oil yield. Under non-stress conditions, foliar application of silicon nanoparticles up to 4 mM significantly increased cumin yield by 44  % and improved yield-related traits compared to controls. This increase is likely due to nSi’s role in enhancing photosynthetic pigments, as shown by Thind et al. (2020) and Rastogi et al. (2021). Under mod- erate drought, nSi effectively mitigated drought-induced impacts on seed yield and yield-related traits. Bijanza- deh, Barati, and Egan (2022) found that 1 mM sodium Figure 5: Average biochemical traits of cumin (Cuminum cyminum L.) under nano-silica foliar application and varying drought stress levels during the 2022-2023 cropping seasons. Differences between means sharing a common letter are not significant according to Duncan's test (α=0.05). Acta agriculturae Slovenica, 121/4 – 20258 M. E. AMERI BAFQI et al. silicate mitigated drought stress in corn. Supporting this, Rastogi et al. (2021) suggested that silicon enhances pho- tosynthesis under stress by preserving chloroplast struc- ture. Consistent with these findings, nSi foliar application significantly increased chlorophyll levels under drought. However, nSi application did not significantly alleviate severe drought stress, and increasing nSi concentration under these conditions showed diminishing returns. Malondialdehyde analysis revealed that nSi con- centrations above 4 mM acted as a stressor, negatively affecting cumin seed yield and related traits. Alzahrani, Kuşvuran, Alharby, Kuşvuran, and Rady (2018) con- cluded that 4 mM Si was optimal for mitigating drought stress in wheat. Verma et al. (2022) similarly found that nSi application enhanced shoot length in barley under drought, while reducing superoxide radical formation and minimizing membrane damage. Drought stress reduces turgor, light absorption, and metabolites needed for cell division. This impairs mito- sis, cell elongation, and expansion, leading to reduced growth, seed yield, and related traits (Sintayehu Musie & Radácsi, 2022). In addition, essential oil yield may vary with seed yield, and observed differences could reflect initial seed proportions or seed-function indices (Bay- ati, Karimmojeni, & Razmjoo, 2020). As mentioned by Bayati et al. (2020) essential oil content reduced in black cumin with intensified drought; however, the decrease was depend on both drought level and genotype, while drought stress may increase essential oil content. Drought stress significantly reduces cumin plant height, contradicting Alinian and Razmjoo (2014) but consistent with Timachi et al. (2023). This reduction like- ly stems from impaired cellular division and elongation under drought conditions (Salajegheh et al., 2021). Fo- liar application of silicon nanoparticles (nSi) effectively alleviates drought-induced height limitations, support- ing Liu and Lal (2015) hypothesis that nanoparticles can mitigate stress-related morphological constraints. This enhancement may be due to nSi deposition in the leaf ap- oplast, creating a protective barrier against environmen- tal stressors (Wang, Hu, Duan, Feng, & Gong, 2016). The growth-promoting effects of nSi are potentially linked to enhanced protein content, nutrient absorption, photo- synthetic efficiency, and reduced cell membrane damage (Raza et al., 2023), as well as increased water and photo- synthetic pigment accumulation during drought. 4.2 EFFECTS OF SILICON NANOPARTICLES AND DROUGHT ON BIOCHEMICAL CHARACTER- ISTICS Drought stress in cumin plants generally reduces total chlorophyll content while increasing peroxidase activity and malondialdehyde levels. The decrease in total chlorophyll content likely results from drought- induced damage to chloroplast structure via ROS, dis- rupting electron transfer in photosystem II (PSII) and impacting chlorophyll content (Hu, Zhang, & Guo, 2023; Qiao, Hong, Jiao, Hou, & Gao, 2024). Plants may also increase stomatal conductance under drought, leading to decreased relative water content in aerial parts (Lv, Li, Chen, Rui, & Wang, 2023). Drought stress elevates peroxidase enzyme activity, a common antioxidant de- fense mechanism against oxidative damage (Zhang & Kirkham, 1994). Foliar application of nSi enhances total chlorophyll content in cumin plants while reducing malondialdehyde levels, an indicator of stress-induced lipid peroxidation. This treatment also increases peroxidase activity, bol- stering the plant’s antioxidant defenses. As reported in previous studies, nSi reduces superoxide radical forma- tion and membrane damage in drought-stressed plants by improving chlorophyll and proline levels, maintain- ing membrane integrity and water content, thus miti- gating drought’s negative effects (Yavaş, 2021). Silicon dioxide nanoparticles may also lessen the impact of drought on photosynthetic pigments by promoting cyto- kinin production, which restores chlorophyll formation and improves chloroplast structure (Khan et al., 2020). Furthermore, nSi enhances nutrient availability, boost- ing photosynthetic efficiency (Asgari, Majd, Jonoubi, & Najafi, 2018), increases cell wall thickness, and facilitates nutrient transport via xylem opening, significantly im- proving photosynthesis (Raza et al., 2023). In coriander, foliar nSi application enhanced antioxidant capacity and increased essential oil yield under moderate drought (Af- shari, Pazoki, & Sadeghipour, 2021). Overall, foliar nSi application can mitigate the adverse effects of drought stress on plants in arid environments (Dilnawaz, Misra, & Apostolova, 2023; El-Beltagi et al., 2024). This study aimed to determine the optimal concen- tration of silicon nanoparticles for alleviating drought stress in cumin plants. Foliar application of 4 mM nSi significantly improved yield and biochemical traits un- der drought conditions. However, a 6 mM concentration had detrimental effects, further reducing these traits. Excessive nSi can cause nutrient imbalances, reduced photosynthesis, and stunted growth. While moderate concentrations can enhance growth and stress resist- ance, excessive levels may hinder root development, cause toxicity, or interfere with nutrient uptake (Karimi & Mohsenzadeh, 2016). Consistent with this, Karimi and Mohsenzadeh (2016) found that nSi concentrations ex- ceeding 200 mg l-1 negatively impacted wheat seedlings, significantly reducing root and shoot fresh and dry mass, Acta agriculturae Slovenica, 121/4 – 2025 9 Modulation of yield and physiological attributes of cumin ... by silicon dioxide nanoparticles under varying drought stresses chlorophyll a and b levels, and carotenoid content, while increasing proline, lipid peroxidation, and catalase activ- ity. They also suggested that lower concentrations (50 and 100 mg l-¹) could have adverse or beneficial effects on wheat seedlings. 5 CONCLUSION Foliar application of nSi at 4 mM significantly im- proves cumin plant growth and physiological resilience under drought. This treatment enhances plant height, grain yield, essential oil yield, and related traits. The benefits of nSi include increased peroxidase activity and chlorophyll content, reduced drought stress, decreased malondialdehyde levels, mitigated reactive oxygen spe- cies, and minimized cellular damage. Therefore, foliar application of nSi at 4 mM is recommended for cumin cultivation; however, concentrations above 4 mM may worsen drought stress. 6 DATA AVAILABILITY The data underlying this study are openly available in Harvard Dataverse at https://dataverse.harvard.edu/ dataset.xhtml?persistentId=doi:10.7910/DVN/BEO42B (Ameri Bafqi, 2025). 7 REFERENCES Abdollah, M. (2009). Effect of planting dates and rows spacing on yield of dryland and irrigated Cumin (Cuminum cyminum L.). Paper presented at the I International medicinal and aromatic plants conference on culinary herbs, Antalya, Turkey. Afshari, M., Pazoki, A., & Sadeghipour, O. (2021). Foliarap- plied silicon and its nanoparticles stimulate physiochemical changes to improve growth, yield and active constituents of coriander (Coriandrum sativum L.) essential oil under different irrigation regimes. Silicon, 13(11), 4177-4188. doi:10.1007/s12633-021-01101-8 Ahmadi Nouraldinvand, F., Seyed Sharifi, R., Siadat, S. A., & Khalilzadeh, R. (2023). Effects of bio-fertilizers and na- no-silicon on phosphorus uptake, grain yield and some physiological traits of wheat (Triticum aestivum L.) un- der withholding irrigation conditions. Environmental Stresses in Crop Sciences, 16(3), 711-726. doi:10.22077/ escs.2023.4931.2090 Alhasnawi, N. J. R., & Al-Bayati, A. S. (2023). Synergistic effects of low tunnel polyethylene covering and silicon spraying on growth and yield of two radish varieties under cold stress. Paper presented at the 4th International Conference of Modern Technologies in Agricultural Sciences, Najaf, Iraq. doi:10.1088/1755-1315/1262/4/042067 Alim, M. A., Hossain, S. I., Ditta, A., Hasan, M. K., Islam, M. R., Hafeez, A. S. M. G., . . . Islam, M. S. (2023). Com- parative efficacy of foliar plus soil application of urea versus conventional application methods for enhanced growth, yield, agronomic efficiency, and economic ben- efits in rice. ACS Omega, 8(39), 35845-35855. doi:10.1021/ acsomega.3c03483 Alinian, S., & Razmjoo, J. (2014). Phenological, yield, essential oil yield and oil content of cumin accessions as affected by irrigation regimes. Industrial Crops and Products, 54, 167- 174. doi:10.1016/j.indcrop.2014.01.028 Alzahrani, Y., Kuşvuran, A., Alharby, H. F., Kuşvuran, S., & Rady, M. M. (2018). The defensive role of silicon in wheat against stress conditions induced by drought, salinity or cadmium. Ecotoxicology and Environmental Safety, 154, 187-196. doi:10.1016/j.ecoenv.2018.02.057 Ameri Bafqi, M. E. (2025). Replication Data for: Modulation of physiological and yield attributes of cumin (Cuminum cyminum L.) by silicon dioxide nanoparticles under vary- ing drought stresses. Retrieved from: doi:10.7910/DVN/ BEO42B Asgari, F., Majd, A., Jonoubi, P., & Najafi, F. (2018). Effects of sil- icon nanoparticles on molecular, chemical, structural and ultrastructural characteristics of oat (Avena sativa L.). Plant Physiology and Biochemistry, 127, 152-160. doi:10.1016/j. plaphy.2018.03.021 Bayati, P., Karimmojeni, H., & Razmjoo, J. (2020). Changes in essential oil yield and fatty acid contents in black cumin (Nigella sativa L.) genotypes in response to drought stress. Industrial Crops and Products, 155, 112764. doi:10.1016/j. indcrop.2020.112764 Bijanzadeh, E., Barati, V., & Egan, T. P. (2022). Foliar applica- tion of sodium silicate mitigates drought stressed leaf struc- ture in corn (Zea mays L.). South African Journal of Botany, 147, 8-17. doi:10.1016/j.sajb.2021.12.032 Chu, M., Liu, M., Ding, Y., Wang, S., Liu, Z., Tang, S., . . . Li, G. (2018). Effect of nitrogen and silicon on rice submerged at tillering stage. Agronomy Journal, 110(1), 183-192. doi:10.2134/agronj2017.03.0156 Deng, C., Wang, Y., Cantu, J. M., Valdes, C., Navarro, G., Cota- Ruiz, K., . . . Gardea-Torresdey, J. L. (2022). Soil and fo- liar exposure of soybean (Glycine max) to Cu: nanoparti- cle coating-dependent plant responses. NanoImpact, 26, 100406. doi:10.1016/j.impact.2022.100406 Desoky, E.-S. M., Mansour, E., El-Sobky, E.-S. E. A., Abdul- Hamid, M. I., Taha, T. F., Elakkad, H. A., . . . Yasin, M. A. T. (2021). Physio-biochemical and agronomic responses of faba beans to exogenously applied nano-silicon under drought stress conditions. Frontiers in Plant Science, 12, 637783. doi:10.3389/fpls.2021.637783 Dilnawaz, F., Misra, A. N., & Apostolova, E. (2023). Involve- ment of nanoparticles in mitigating plant’s abiotic stress. Plant Stress, 10, 100280. doi:10.1016/j.stress.2023.100280 Dunne, R. P. (2010). Synergy or antagonism—interactions be- tween stressors on coral reefs. Coral Reefs, 29(1), 145-152. doi:10.1007/s00338-009-0569-6 El-Beltagi, S. H., Mubarak Alwutayd, K., Rasheed, U., Sattar, A., Acta agriculturae Slovenica, 121/4 – 202510 M. E. AMERI BAFQI et al. Ali, Q., Alharbi, M. B., . . . Hamada, M. A. M. (2024). Sole and combined foliar application of silicon and putrescine alleviates the negative effects of drought stress in maize by modulating the morpho-physiological and antioxidant defence mechanisms. Plant, Soil and Environment, 70(1), 26-39. Fageria, N. K., Filho, M. P. B., Moreira, A., & Guimarães, C. M. (2009). Foliar fertilization of crop plants. Journal of Plant Nu- trition, 32(6), 1044-1064. doi:10.1080/01904160902872826 Frew, A., Weston, L. A., Reynolds, O. L., & Gurr, G. M. (2018). The role of silicon in plant biology: a paradigm shift in research approach. Annals of Botany, 121(7), 1265-1273. doi:10.1093/aob/mcy009 Ghorbanpour, M., Mohammadi, H., & Kariman, K. (2020). Nanosilicon-based recovery of barley (Hordeum vulgare) plants subjected to drought stress. Environmental Science: Nano, 7(2), 443-461. doi:10.1039/C9EN00973F Gomez, K. A., & Gomez, A. A. (2009). Statistical procedures in agricultural research (January 1, 2009 ed.): John Wiley & Sons. Haghighi, M., & Pessarakli, M. (2013). Influence of silicon and nano-silicon on salinity tolerance of cherry tomatoes (So- lanum lycopersicum L.) at early growth stage. Scientia Hor- ticulturae, 161, 111-117. doi:10.1016/j.scienta.2013.06.034 Helaly, M. N., El-Hoseiny, H., El-Sheery, N. I., Rastogi, A., & Kalaji, H. M. (2017). Regulation and physiological role of silicon in alleviating drought stress of mango. Plant Physiology and Biochemistry, 118, 31-44. doi:10.1016/j. plaphy.2017.05.021 Hu, F., Zhang, Y., & Guo, J. (2023). Effects of drought stress on photosynthetic physiological characteristics, leaf micro- structure, and related gene expression of yellow horn. Plant Signaling & Behavior, 18(1), 2215025. doi:10.1080/1559232 4.2023.2215025 Johri, R. K. (2011). Cuminum cyminum and Carum car- vi: An update. Pharmacognosy Reviews, 5(9), 63-72. doi:10.4103/0973-7847.79101 Karimi, J., & Mohsenzadeh, S. (2016). Effects of silicon oxide nanoparticles on growth and physiology of wheat seed- lings. Russian Journal of Plant Physiology, 63(1), 119-123. doi:10.1134/S1021443716010106 Khan, Z. S., Rizwan, M., Hafeez, M., Ali, S., Adrees, M., Qayy- um, M. F., . . . Sarwar, M. A. (2020). Effects of silicon nano- particles on growth and physiology of wheat in cadmium contaminated soil under different soil moisture levels. Envi- ronmental Science and Pollution Research, 27(5), 4958-4968. doi:10.1007/s11356-019-06673-y Kovács, S., Kutasy, E., & Csajbók, J. (2022). The multiple role of silicon nutrition in alleviating environmental stress- es in sustainable crop production. Plants, 11(9), 1223. doi:10.3390/plants11091223 Leroy, N., de Tombeur, F., Walgraffe, Y., Cornélis, J.-T., & Ver- heggen, F. J. (2019). Silicon and plant natural defenses against insect pests: impact on plant volatile organic com- pounds and cascade effects on multitrophic interactions. Plants, 8(11), 444. doi:10.3390/plants8110444 Lichtenthaler, H., & Wellburn, A. R. (1985). Determination of total carotenoids and chlorophylls a and b of leaf in differ- ent solvents. Biochemical Society Transactions, 11, 591-592. Liu, R., & Lal, R. (2015). Potentials of engineered nanoparticles as fertilizers for increasing agronomic productions. Science of The Total Environment, 514, 131-139. doi:10.1016/j.scito- tenv.2015.01.104 Lv, X., Li, Y., Chen, R., Rui, M., & Wang, Y. (2023). Stomatal responses of two drought-tolerant barley varieties with dif- ferent ROS regulation strategies under drought conditions. Antioxidants, 12(4), 790. doi:10.3390/antiox12040790 Maehly, A. C. (1954). The assay of catalases and peroxidases. In Methods of Biochemical Analysis (pp. 357-424). Mir, R. A., Bhat, B. A., Yousuf, H., Islam, S. T., Raza, A., Rizvi, M. A., . . . Zargar, S. M. (2022). Multidimensional role of sil- icon to activate resilient plant growth and to mitigate abiot- ic stress. Frontiers in Plant Science, 13, 819658. doi:10.3389/ fpls.2022.819658 Mohammadi, H., Abdollahi-Bastam, S., Aghaee, A., & Ghor- banpour, M. (2024). Foliar-applied silicate potassium mod- ulates growth, phytochemical, and physiological traits in Cichorium intybus L. under salinity stress. BMC Plant Biol- ogy, 24(1), 288. doi:10.1186/s12870-024-05015-6 Noori, H., Moosavi, S. G., Seghatoleslami, M. J., & Fazeli Ros- tampour, M. (2022). Morpho-physiological and yield responses of cumin (Cuminum cyminum L.) to the appli- cation of growth regulators under drought stress. Iranian Journal of Plant Physiology, 1(12), 4013-4025. doi:10.30495/ ijpp.2022.689076 Qiao, M., Hong, C., Jiao, Y., Hou, S., & Gao, H. (2024). Impacts of drought on photosynthesis in major food crops and the related mechanisms of plant responses to drought. Plants, 13(13), 1808. doi:10.3390/plants13131808 Rastogi, A., Yadav, S., Hussain, S., Kataria, S., Hajihashemi, S., Kumari, P., . . . Brestic, M. (2021). Does silicon really mat- ter for the photosynthetic machinery in plants…? Plant Physiology and Biochemistry, 169, 40-48. doi:10.1016/j. plaphy.2021.11.004 Raza, M. A. S., Zulfiqar, B., Iqbal, R., Muzamil, M. N., Aslam, M. U., Muhammad, F., . . . Habib-ur-Rahman, M. (2023). Morpho-physiological and biochemical response of wheat to various treatments of silicon nano-particles under drought stress conditions. Scientific Reports, 13(1), 2700. doi:10.1038/s41598-023-29784-6 Rudra Pratap, S., Gangadharappa, H. V., & Mruthunjaya, K. (2017). Cuminum cyminum – A popular spice: An updated review. Pharmacognosy Journal, 9(3), 292-301. doi:10.5530/ pj.2017.3.51 Safari, B., Mahdi Mortazavian, S. M., Sadat-Noori, S. A., & Foghi, B. (2015). Effect of water stress on yield and yield components of cumin (Cuminum cyminum L.) ecotypes. Journal of Plant Physiology and Breeding, 5(2), 51-61. Salajegheh, M., Yavarzadeh , M., Payandeh, A., & Akbarian, M. M. (2021). Effects of titanium and silicon nanoparticles and super absorbent polymer on morphological and functional traits of cumin plant under drought stress. International Journal of Modern Agriculture, 10(3), 189 - 200. Samal, I., Bhoi, T. K., Mahanta, D. K., & Komal, J. (2024). Es- tablishing the role of silicon (Si) in plant resistance to in- sects: A bibliometric approach. Silicon, 16(5), 2119-2128. doi:10.1007/s12633-023-02821-9 Acta agriculturae Slovenica, 121/4 – 2025 11 Modulation of yield and physiological attributes of cumin ... by silicon dioxide nanoparticles under varying drought stresses SAS. (2003) (Version Release 9.1 for windows). Cary, NC, USA.: SAS Institute Inc. Senthilkumar, M., Amaresan, N., & Sankaranarayanan, A. (2021). Estimation of malondialdehyde (MDA) by thio- barbituric acid (TBA) assay. In Plant-Microbe Interac- tions: Laboratory Techniques (pp. 103-105). New York, NY: Springer US. Sharma, B., Kumawat, K. C., Tiwari, S., Kumar, A., Dar, R. A., Singh, U., & Cardinale, M. (2023). Silicon and plant nu- trition—dynamics, mechanisms of transport and role of silicon solubilizer microbiomes in sustainable agriculture: A review. Pedosphere, 33(4), 534-555. doi:10.1016/j.ped- sph.2022.11.004 Sintayehu Musie, M., & Radácsi, P. (2022). Influence of drought stress on growth and essential oil yield of ocimum species. Horticulturae, 8(2), 175. doi:10.3390/horticulturae8020175 Sowbhagya, H. B. (2013). Chemistry, technology, and nutra- ceutical functions of cumin (Cuminum cyminum L): An overview. Critical Reviews in Food Science and Nutrition, 53(1), 1-10. doi:10.1080/10408398.2010.500223 Sutulienė, R., Ragelienė, L., Samuolienė, G., Brazaitytė, A., Ur- butis, M., & Miliauskienė, J. (2022). The response of antiox- idant system of drought-stressed green pea (Pisum sativum l.) affected by watering and foliar spray with silica nano- particles. Horticulturae, 8(1), 35. doi:10.3390/horticultu- rae8010035 Teimoori, N., Ghobadi, M., & Kahrizi, D. (2023). Improving the growth characteristics and grain production of camelina (Camelina sativa L.) under salinity stress by silicon foliar application. Agrotechniques in Industrial Crops, 3(1), 1-13. doi:10.22126/atic.2023.8681.1081 Thind, S., Hussain, I., Ali, S., Hussain, S., Rasheed, R., Ali, B., & Hussain, H. A. (2020). Physiological and biochemical bases of foliar silicon-induced alleviation of cadmium toxicity in wheat. Journal of Soil Science and Plant Nutrition, 20(4), 2714-2730. doi:10.1007/s42729-020-00337-4 Timachi, F., Armin, M., Jamimoeini, M., & Abhari, A. (2023). The effect of times and type of stress modulator on quanti- tative and qualitative yield of cumin under rainfed and ir- rigated conditions. Journal of Medicinal plants and By-Prod- ucts, 12(2), 145-157. doi:10.22092/jmpb.2021.341798.1182 Valdés, A., & Ehrlén, J. (2022). Microclimate influences plant reproductive performance via an antagonistic interac- tion. Basic and Applied Ecology, 64, 13-29. doi:10.1016/j. baae.2022.07.007 Verma, K. K., Song, X.-P., Singh, M., Huang, H.-R., Bhatt, R., Xu, L., . . . Li, Y.-R. (2022). Influence of nanosilicon on drought tolerance in plants: An overview. Frontiers in Plant Science, 13. doi:10.3389/fpls.2022.1014816 Wang, Y., Hu, Y., Duan, Y., Feng, R., & Gong, H. (2016). Sili- con reduces long-term cadmium toxicities in potted garlic plants. Acta Physiologiae Plantarum, 38(8), 211. doi:10.1007/s11738-016-2231-6 Xiao, J., Li, Y., & Jeong, B. R. (2022). Foliar silicon spray to strawberry plants during summer cutting propagation enhances resistance of transplants to high temperature stresses. Frontiers in Sustainable Food Systems, 6, 938128. doi:10.3389/fsufs.2022.938128 Yavaş, İ. (2021). The effect of nanoparticle applications on plants under some stress conditions. Turkish Journal of Range and Forage Science, 2. doi:10.51801/turkjrfs.954843 Zhang, J., & Kirkham, M. B. (1994). Drought-stress-induced changes in activities of superoxide dismutase, catalase, and peroxidase in wheat species. Plant and Cell Physiology, 35(5), 785-791. doi:10.1093/oxfordjournals.pcp.a078658