Jasminum sambac (Arabian jasmine) belongs to the family Oleaceae and is extensively cultivated in tropical regions for its aromatic flowers and essential oil production Ghissing et al., (2022). Commercial success depends on flower production and quality, which are affected by water supply, nutrients and abiotic stresses Suganya et al., (2023). Silicon (Si), recognized as quasi-essential, enhances plant growth and stress tolerance, increasing productivity in many crops Luyckx et al., (2017).
               
Silicon improves photosynthesis, water relations and antioxidant defense, thereby enhancing plant growth and stress tolerance Ahmed and Al-Tameemi (2025). Si deposition in tissues contributes to cellular stability and Si-supplemented plants show increased antioxidant enzyme activity and reduced oxidative damage markers Sapre and Vakharia (2016). Studies have shown that silicon enhances visual quality and yield in floriculture. However, the comparative bioavailability of different silicon sources, their dose-dependent effects on growth, antioxidant responses and flower yield in Jasminum sambac remain poorly understood. We hypothesize that sodium metasilicate, due to its higher solubility, will outperform calcium silicate in improving plant performance. The present study compares sodium metasilicate and calcium silicate at two concentrations (1 and 5 mM) under non-stress conditions, aiming to evaluate their comparative bioavailability and effects on growth, physiological responses, antioxidant activity and flower yield in Jasminum sambac. 

Jasminum sambac (L.) Aiton (Madurai Malli) was cultivated in a controlled greenhouse with relative humidity maintained at 60-70% and temperatures at 30-32^oC under a 16 h light/8 h dark photoperiod during 2022-2023. The experiment was conducted at the Vellore Institute of Technology, Vellore, India (Lat. 12^o58'5.94"N, Lon.79^o 9'41.39"E). Uniform jasmine stem cuttings were collected from five-year-old healthy mother plants grown in a farmer’s field in Madurai, Tamil Nadu, to ensure genetic uniformity. The cuttings were rooted and maintained under nursery conditions for three months to obtain vigorous and uniform saplings. Three-month-old saplings were transplanted into experimental pots (30 cm diameter ×  25 cm height) containing a potting mixture of farmyard manure, red soil and coarse sand (2:1:1, v/v). The initial physicochemical properties of the potting mixture (red soil + FYM + sand) were: pH 6.5, electrical conductivity (EC) 1.1 dS m^-1 and available silicon 58 mg kg^-1 (expressed as SiO₂).
       
Silicon treatments consisted of sodium metasilicate (1 and 5 mM) and calcium silicate (1 and 5 mM), along with an untreated control. Silicon was supplied as sodium metasilicate (Na₂SiO₃, analytical grade, ~98-100% purity, Sigma-Aldrich) and calcium silicate (purum grade, ≥ 87% SiO₂ basis, Sigma-Aldrich). These sources were selected based on previous studies on stress conditions. Sodium metasilicate provides readily available monosilicic acid in the soil solution, whereas calcium silicate improves growth and yield (Al Murad and Muneer, 2022; Wang et al., 2021a).
       
The experiment was conducted in a completely randomized design (CRD) with five treatments and six replicates, with a total of 30 pots. Each pot contained one plant (Fig 1). Pots were randomly positioned and shifted within the greenhouse to minimize positional effects. Silicon treatments were applied as a single soil drench (100 mL/pot) at 10 days after transplanting and no further applications were made during the experimental period up to 30 days. Growth parameters, including shoot length and root length, were recorded. SPAD meter was measured using a (Konica Minolta, Tokyo, Japan). SPAD values (chlorophyll values) were recorded and the equations based on the modulations given by Huntingford et al., (2015) were used to derive the net photosynthesis rate, transpiration rate and stomatal conductance. Fresh leaf samples collected on these days were cleaned and stored at -80°C for further experiments. Chlorophyll fluorescence (Fv/Fm) was measured using a Mini-PAM 2000 fluorometer following 30 min of dark adaptation (Heinz Walz, Germany). Chlorophyll content was measured using the DMSO method (Muneer et al., 2012).

 
d = Cuvette path length (usually 1cm).
w = Fresh weight (g).
v = Volume of the extraction medium.


       
Fresh and dry weights were recorded on the 10^th, 20^th and 30^th days after treatment initiation. The plants were carefully uprooted and washed to remove adhering soil and immediately weighed to determine the fresh weight. For dry weight, the samples were dried in hot air oven for 48 h at 65^oC.
       
Total soluble protein was estimated using the Bradford method with BSA as the standard. Fresh leaves (0.2 g) were homogenized with extraction buffer (50 mM sodium phosphate buffer) containing 2% PVP, 0.5% Triton X-100 and 1 mM EDTA.  Samples were maintained at 4^oC during extraction and centrifuged at 12000 rpm for 20 min at 4^oC.  Absorbance was measured at 595 nm and protein content was expressed as mg/g (FW) (Bradford, 1976).
       
For antioxidant enzyme (SOD, CAT, or APX) extraction, the extraction mixture contained 50 mM potassium phosphate buffer (pH 7.5), 1% PVP, 1% Triton X-100 and 3.8 mM EDTA. Fresh tissues (0.2 g) were homogenized with buffer and centrifuged at 10,000 rpm at 4^oC. SOD activity was determined by NBT reduction inhibition Venkat et al., (2023). For catalase, samples were processed similarly and reacted with phosphate buffer and H₂O₂ and absorbance was measured at 240 nm (Choudhary et al., 2012).
       
APX activity was assessed using similar extraction conditions, with 0.3 g of tissue homogenized and centrifuged. The reaction mixture contained phosphate buffer, EDTA, ascorbate and H₂O₂ and absorbance was measured at 290 nm (Costa et al., 2005). H₂O₂  content was determined by homogenizing leaf tissues with 0.1% TCA, mixing the supernatant with potassium iodide and measuring the absorbance at 390 nm Pereira et al., (2018).                         

All enzyme activities (SOD, CAT and APX) were expressed as U mg^-1 protein. MDA content was determined using the TBARS assay. Leaf tissue (0.3 g) was homogenized with 1% TCA, centrifuged at 7000 rpm for 5 min and 1 mL supernatant was mixed with 4 mL of 0.5% TBA. After incubating at 95^oC for 30 min, absorbance was measured at 532 nm, with corrections at 600 nm Heath and Packer (1968). Proline content was estimated as described by Zdunek-Zastocka et al. (2021). Leaf samples (0.3 g) were homogenized and centrifuged at 3000 rpm for 20 min. The supernatant was mixed with acid ninhydrin reagent and glacial acetic acid, heated at 100^oC for 60 min, cooled on ice with toluene and measured at 520 nm.
       
Freshly harvested flowers were used to measure the corolla tube length using a digital vernier caliper and individual flower weight was measured using a weighing balance. Flowers were harvested between 6:00 and 8:00 a.m. during peak flowering and were measured immediately to minimize moisture loss (Patel et al., 2017).
       
Data were analyzed using one-way ANOVA followed by Tukey’s HSD post hoc test at p≤0.05 using JMP software (SAS Institute, Cary, NC, USA). Data represent treatment means of six replicates ± standard error (SE).

Silicon supplementation enhanced the morphological and physiological parameters of Jasminum sambac in a dose and source-dependent manner. Among the treatments, sodium metasilicate at 5 mM (NaSi 5 mM) showed the most significant positive effects. Plant growth responses are presented in (Fig 2A-D). Sodium metasilicate (5 mM) significantly improved vegetative growth, increasing shoot and root length, leaf number and branching compared to the control plants. Representative plants images are shown in Fig 3  visual assessment showed that silicon treatments modified root architecture, with NaSi (5 mM) promoting more fibrous root systems (Fig 4).






       
The fresh weight increased by 21.43% on day 10 with NaSi (5 mM). By day 20 and 30, the fresh weight increased by 19.08% and 26.9%, respectively, while the dry weight increased by 25.93% and 59.71%, respectively. CaSi treatments showed no significant difference from the controls (Fig 5A-B).


       
Silicon supplementation significantly improved photosynthetic performance, with NaSi (5 mM) showing the highest increases in photosynthetic rate, stomatal conductance and transpiration rate. The maximum quantum yield increased by 28.7%, 23.9% and 47.4% with sodium metasilicate 5 mM, while the PS-II quantum yield decreased in calcium silicate treatments (Fig 6). The NaSi (5 mM) treatment maintained the highest chlorophyll levels, with increases of 9.6%, 13% and 45.1% on days 10, 20 and 30.


       
Sodium metasilicate (5 mM) significantly increased antioxidant enzyme activities (SOD, CAT and APX) (Fig 7A-C). CaSi (5 mM) showed the highest MDA and H₂O₂ contents, whereas NaSi (5 mM) recorded the lowest values. In NaSi (5 mM)-treated plants, MDA declined by 14.7%, 22.5% and 33% and H₂O₂ decreased by 24.5%, 7.1% and 29.5%. CaSi (1 mM) accumulated the most proline, whereas NaSi (5 mM) showed reduced proline content (Fig 8A-C).




       
Soluble protein content increased across treatments, with NaSi (5 mM) showing the highest levels throughout the study period, suggesting that sodium metasilicate was more effective than calcium silicate (Fig 9A). Silicon treatments did not affect Jasminum sambac corolla tube length but significantly impacted flower bud weight. NaSi (5 mM) produced the highest individual bud weight, followed by NaSi (1 mM) and CaSi (5 mM), while CaSi  (1 mM) showed the lowest yield, below control levels. Similarly, for hundred flower bud weight, NaSi (5 mM) showed the highest mass, with NaSi (1 mM) and CaSi (5 mM) showing moderate values and CaSi (1 mM) the lowest. Flower bud weight and hundred flower bud weight increased by 55.6% and 44.6%, respectively. Higher Na-silicate levels increased floral biomass, whereas low Ca-silicate reduced bud weight compared with the controls (Fig 10).




       
This study examined the effects of silicon on Jasminum sambac growth and yield. Treatment with 5 mM sodium metasilicate enhanced shoot length compared to the control, while also improving root length (Fig 2). Silicon promotes shoot and root elongation (Bijanzadeh et al., 2022); (Zhou et al., 2018). Leaves and branches increased with 5 mM sodium metasilicate, indicating enhanced lateral meristem activity, similar to findings in gladiolus Sameer et al., (2024). Calcium silicate had weaker effects than sodium metasilicate El-Sayed et al. (2025). This difference may be attributed to the higher solubility and bioavailability of sodium metasilicate, which readily releases monosilicic acid, the plant-available form of silicon, whereas calcium silicate releases silicon more slowly.  Fresh and dry weights increased under 5 mM sodium metasilicate, consistent with previous reports Sinky et al., (2024). Silicon improved photosynthetic performance and gas exchange, consistent with previous studies Liang et al., (2023); Mukarram et al., (2026). The maximum quantum efficiency of photosystem II (PSII; Fv/Fm) increased under sodium metasilicate treatment, indicating improved photosynthetic efficiency  (Li et al., 2022). Exogenous Si increased Fv/Fm, Y(II) and electron transport rate while reducing photoinhibition Rastogi et al., (2021). Sodium metasilicate increased chlorophyll and carotenoid content by stabilizing chloroplasts (Al Murad and Muneer, 2022). Silicon enhances pigment content and photosynthetic rates (Sameer et al., 2024) acting as a pigment stabilizer and photosynthetic stimulant, with 5 mM sodium metasilicate optimally supporting jasmine flowering physiology.
       
The activity of antioxidant enzymes in Jasminum sambac under 5 mM sodium metasilicate strengthens enzymatic defense against oxidative stress. Increased SOD, CAT and APX activities indicate that silicon strengthens antioxidant defense systems and reduces the accumulation of reactive oxygen species. SOD and CAT peaked on day 30 with sodium metasilicate treatment, indicating that Si maintains antioxidant functionality (Manimaran et al., 2025). The total soluble protein content increased with 5 mM sodium metasilicate treatment, indicating improved metabolic integrity, similar to findings for date palms and sugar beets Al-Mayahi (2016).
       
The observed reduction in H₂O₂ and MDA levels indicates lower basal oxidative stress and reduced lipid peroxidation, reflecting improved membrane stability and cellular integrity. Although reactive oxygen species (ROS), such as H₂O₂ are naturally produced during normal metabolic processes, their accumulation can still impair proteins, membranes and photosynthetic machinery (Gou et al., 2023). The decline in ROS levels in silicon-treated plants suggests enhanced antioxidant capacity, which helps maintain cellular homeostasis and protects metabolic functions even under non-stress conditions. The reduced proline accumulation further indicates a lower physiological stress status and improved metabolic balance. Improved membrane integrity and redox regulation likely contributed to enhanced photosynthetic efficiency and better resource utilization, resulting in improved growth and yield traits in Jasminum sambac (Li et al., 2025). Yield traits improved under treatment, with increased corolla tube length and flower bud weights (Swaroop et al., 2023), demonstrating silicon’s role in reducing stress while improving protein status and floral yield in J. sambac. Although silicon is widely recognized for its role under stress conditions, the present study demonstrates that silicon supplementation can also enhance growth, physiological performance and antioxidant capacity under non-stress conditions, highlighting its broader role in improving plant productivity. This study evaluated only two silicon concentrations (1 and 5 mM) and a broader range of concentrations may help identify optimal thresholds and potential toxicity levels. Additionally, the experiment was conducted using a single jasmine cultivar (‘Madurai Malli’) and responses to silicon application may vary among different cultivars. Therefore, further studies across a wider range of concentrations and multiple cultivars are recommended.

This study found that 5 mM sodium metasilicate was the optimal silicon source for enhancing the vegetative, physiological and biochemical performance of Jasminum sambac. Silicon supplementation improved shoot and root growth, photosynthetic efficiency, chlorophyll content, antioxidant enzyme activity, protein levels and flower yield, while reducing oxidative stress. Silicon demonstrated structural improvement, photosynthetic optimization and yield enhancement under non-stress conditions. Sodium metasilicate showed higher efficiency than calcium silicate, indicating better bioavailability and absorption. Silicon fertilization represents an effective strategy for improving jasmine growth and quality and addressing physiological and economic challenges in commercial floriculture. Soil drench application of 5 mM sodium metasilicate can be recommended to enhance flower yield and quality in jasmine cultivation. Further studies under field conditions across different soil types and water regimes are needed to validate these findings and assess long-term effects on essential oil composition.

The present study was supported by Vellore Institute of Technology.
 
Disclaimers
 
The views and conclusions expressed in this article are solely those of the authors and do not necessarily represent the views of their affiliated institutions. The authors are responsible for the accuracy and completeness of the information provided.
 
Informed consent
 
Not applicable as the study did not involve human participants or animals.

The authors declare no conflicts of interest related to the publication of this article.