INTRODUCTION
Wheat (Triticum aestivum L .) is one of t he world’s most vital cereal crops, serving as a staple food for nearly 35% of the global population (Afzal et al., 2015). Common wheat accounts for approximately 95% of global wheat production, while durum wheat, primarily used for pasta and couscous, constitutes the remaining 5% (De Sousa et al., 2021;Khalid et al., 2023). The global production of wheat is estimated at 766 million tons, spanning 216 million hectares across over 25 countries (Sharma et al., 2022), with Asia being the leading producer, followed by Europe, the Americas, Oceania, and Africa (Erenstein et al., 2022). Wheat contributes more calories and protein to the human diet than any other cereal (Igrejas and Branlard, 2020) and is valued for its high protein, essential mineral, B-group vitamin, and dietary fiber levels (Kumar et al., 2011). Wheat’s versatility is demonstrated in its use in bread, noodles, confectionery, and vital wheat gluten (Shewry, 2009). It plays important roles in animal feed, ethanol production, and cosmetics, while its straw is incorporated into composite materials (Yasina et al., 2010). Wheat germ and bran, which are rich in dietary fiber, contribute to digestive health (Cheng et al., 2022). However, challenges such as poor seedling emergence and crop establishment, which significantly reduce yields (McMaster et al., 2002;Passioura, 2006), must be addressed to maintain wheat productivity and satisfy growing global demand.
Seed germination is a critical process that triggers seedling development by breaking dormancy and initiating metabolic changes (Nonogaki et al., 2010;2014;Khaeim et al., 2022). This process involves water uptake, enzyme activation, and the mobilization of stored reserves to support early growth (Ali and Elozeiri, 2017). Successful germination directly impacts crop yield and plant health (Prasad et al., 2009), whereas poor germination often leads to reduced wheat establishment and yield (Ashraf and Foolad, 2005). Factors such as low seed quality, inadequate moisture, and poor soil conditions can hinder germination (Farooq et al., 2008). To overcome these challenges, seed priming, a pre-sowing treatment method that hydrates seeds to initiate germination processes without radicle emergence, improves seedling establishment and crop performance (Bradford, 1986). Priming accelerates germination and enhances uniformity through increased enzyme activity and metabolic efficiency (Waqas et al., 2019), and studies have revealed its benefits in wheat, barley, and maize (Nawaz et al., 2013).
Although seed priming demonstrates significant promise, limited research has investigated the optimal priming conditions for wheat (Ahmad et al., 2018). Recent studies suggest that priming with Silicon (Si) can enhance seed germination, seedling growth, and crop resilience under environmental stress (Qados et al., 2014;Shi et al., 2014;Biju et al., 2017). Si has exhibited potential in boosting germination rates, promoting seedling vigor, and improving crop resilience under environmental stress. Seed priming, a pre-sowing treatment technique, improves germination and seedling establishment by partially hydrating seeds to synchronize germination (Bradford, 1986). It has been shown to enhance crop yields in wheat, barley, and maize (Nawaz et al., 2013) by accelerating germination and heightening metabolic and antioxidant activity (Waqas et al., 2019). Although research on the optimal priming conditions for wheat is limited (Ahmed et al., 2019), Si priming has displayed potential to improve seed germination and growth (Ali et al., 2021).
This study aimed to determine the most effective Si concentrations and priming durations for enhancing wheat germination and seedling growth. Despite the benefits of Si priming are recognized, the optimal conditions for its application, particularly in wheat, remain unclear. Addressing this gap is imperative, as identifying the precise priming parameters may significantly improve wheat seedling establishment and overall crop performance. We hypothesized that varying Si concentrations in seed priming potentially enhance seed germination and seedling growth. The objectives were therefore to (1) evaluate the effects of Si-based seed priming on wheat germination and seedling development and (2) identify the concentrations and priming durations that most effectively promote wheat seedling growth and crop performance.
MATERIALS AND METHODS
Planting materials, treatments, and experimental design
Wheat seeds, a landrace variety (재래종), were obtained from Agricultural Corporation Cheongnong Seed Co., Ltd., Republic of Korea. This variety was chosen for its adaptability to local agro-climatic conditions, excellent seed quality with an 85% germination rate, and its potential to benefit from silicon-based priming to further enhance seedling growth and crop productivity. The priming agents evaluated in this study included Si, supplied as sodium metasilicate pentahydrate (Na2SiO3ㆍ5H2O), and distilled water (H2O). Six treatment groups were used: a control (non-primed), hydropriming (water-primed), and Si priming at concentrations of 0.25, 0.5, 0.75, and 1 mM. The priming solutions were prepared by thoroughly dispersing the agents in distilled water using a vortex shaker for 15 minutes (min), following the protocol described by Raja et al. (2019). The experiment was conducted in May 2024 at the Crop Production Laboratory, Kyungpook National University, Republic of Korea, utilizing the “Top of Paper” germination method. The experimental layout followed a completely randomized design, with three replications per treatment group.
Priming of wheat seeds
Wheat seeds were surface-sterilized by immersion in a 5% volume/volume (v/v) sodium hypochlorite solution for 5 min to eliminate potential microbial contaminants, according to the protocol of Salehzade et al. (2009). After sterilization, the seeds were thoroughly rinsed three times with distilled water to ensure the complete removal of residual chemicals. Subsequently, the sterilized seeds were subjected to priming treatments using Si solutions at four different concentrations (0.25, 0.5, 0.75, and 1 mM), alongside a hydropriming treatment (distilled water) as a comparative measure. Non-treated seeds were used as a control. Original priming solutions were prepared for each treatment, with the seed-to-solution ratio set at 1:5 weight/volume (w/v) to ensure uniform hydration, as per the method of Khan et al. (2019). The seeds were exposed to the priming agents for soaking periods of 4, 6, and 8 hours (h). Thereafter, excess priming solution was removed by draining the seeds through a fine sieve, followed by gentle blotting to remove surface moisture. The primed seeds were subsequently dried back to approximately their original moisture content (12%) to stabilize their physiological state using a forced convection oven (JSON-150; Natural Convection Oven, Gongju-City, Korea) set at 25°C for 48 h before conducting the germination assays (Fig. 1).
Germination testing of wheat seeds
Germination testing was performed using a sample of 25 primed seeds from each treatment group (Fig. 1). The seeds were uniformly spaced in 9-centimeters (cm) diameter Petri dishes, ensuring a separation distance of at least three times the seed size to prevent overlap and promote uniform growth. The germination substrate comprised two layers of tissue paper that acted as a moisture-retentive medium. To initiate germination, 10 milliliters (ml) of distilled water was precisely added to the substrate, following the protocol outlined by Sghayar et al. (2023), to achieve the desired moisture levels. The Petri dishes were securely sealed to minimize evaporative water loss and subsequently placed in a germination chamber maintained at 23 ± 2°C. The environmental conditions in the chamber were controlled, with a photoperiod entailing 16 h of light and 8 h of darkness as well as a stable relative humidity of 50%, as recommended by Oğuz et al. (2023). The moisture content of the germination substrate was carefully monitored daily to ensure its consistency throughout the experimental period. Distilled water was added as necessary to maintain optimal moisture levels, thus providing consistent and reproducible germination conditions across all treatment groups.
Study parameters
In this experiment, seven parameters were classified into two categories: germination and growth parameters, and they were subsequently evaluated. The germination parameters included germination percentage (GP), germination index (GI), and vigor index (VI), while the growth parameters comprised radicle length (RL), plumule length (PL), seedling fresh weight (SFW), and seedling dry weight (SDW). Germination was operationally defined as the emergence of approximately 2 millimeters (mm) of the radicle from the seed coat, in accordance with the criteria established by Abnavi and Ghobadi (2012). Following a 120-h incubation period, 10 seedlings were randomly selected from each experimental unit, and the corresponding parameters were measured. The procedures for assessing each parameter are presented in Table 1.
Statistical Analysis
All data were examined via analysis of variance (ANOVA) using R Studio (version 4.4.0), and mean comparisons between treatment groups were performed using Duncan’s multiple-range test. Statistical significance was set at p < 0.05. Correlation coefficients for the measured parameters were also calculated using R Studio (version 4.4.0). Furthermore, all figures and analytical outputs were generated using Microsoft Excel (version 10).
RESULTS
Analysis of variance of germination and seedling growth
The ANOVA results for seed priming with Si revealed significant differences in GP, GI, VI, RL, PL, and SDW, with p-values ranging from 0.02 to < 0.001, while no significant variation in SFW was observed (Table 2). Similarly, significant interaction effects between the treatment and priming duration were observed for RL, PL, and SFW, indicating that these parameters were influenced by both factors. In contrast, no significant interaction effects were detected for GP, GI, VI, and SDW, suggesting that these parameters remained unaffected by the variation in priming duration.
Effect of Si on the GP of wheat
Si priming significantly affected GP across various concentrations and durations compared with the control (Fig. 2). Notably, Si concentrations of 1 and 0.75 mM, over priming durations of 4, 6, and 8 h, resulted in substantial GP improvements. The highest GP values, that is, 98%, 100%, and 97.3%, were observed with Si priming at 1 mM concentration after 4, 6, and 8 h, respectively, demonstrating a clear enhancement over the control. Si priming at a concentration of 1 mM elicited notable GP increases of 10.8%, 10.6%, and 8.2% when applied for 4, 6, and 8 h, respectively, compared with the control. Similarly, the same Si priming treatment improved GP by 5.33%, 9.34%, and 4 % compared with hydropriming over the same durations of 4, 6, and 8 h, respectively (Fig. 2).
Effects of Si on the GI and VI of Wheat
Si priming significantly influenced the GI of wheat seeds across different concentrations and durations compared with the control (Fig. 3a). Significant increases in GI were observed at Si concentrations of 0.75 and 1 mM after 4 h, 0.5 and 1 mM after 6 h, and 0.75 and 1 mM after 8 h. Among these treatments, the highest GI, 55, was recorded at 1 mM after 6 h, followed by 50 at both 0.75 mM (4 h) and 1 mM (8 h), compared with that yielded by the control. In contrast, hydropriming generated GI values of 40, 44, and 44 after 4, 6, and 8 h, respectively, relative to the control (Fig. 3a). After 6 h, Si priming at 1 mM increased the GI by 65.5% and 16% compared with the control and hydropriming treatments, respectively. Si-based seed priming at varying concentrations and durations caused a significant increase in seedling VI compared with the control (Fig. 3b). The highest VI value of 632.66 was recorded for Si priming at a concentration of 1 mM after 6 h, whereas the lowest of 444.69 was observed in the hydropriming treatment. After 6 h, Si priming at 1 mM resulted in 29.4% and 29.71% increases in VI compared with the control and hydropriming treatments, respectively (Fig. 3b).
Effects of Si on the RL and PL of wheat
Si-based seed priming significantly influenced RL at varying concentrations and durations compared with the control (Fig. 4a). The most notable effect was observed at a Si concentration of 0.5 mM after 4 h of priming, which resulted in a significant increase in RL relative to the control. The longest RL of 0.89 cm was attained with 1 mM Si priming, whereas the shortest RLs of 0.51 and 0.56 cm were observed in the control and hydropriming treatments, respectively. Likewise, after 6 h, Si priming at 1 mM increased RL by 18.61% and 28.66% compared with the control and hydropriming treatments, respectively. Si priming also significantly increased PL across varying concentrations and durations compared with the control (Fig. 4b). The longest PL of 1.67 cm was achieved with 0.25 mM Si after 4 h of priming, whereas the shortest PL of 1.07 cm was noted in the control group after 6 h of priming. After 6 h, Si priming at 1 mM elicited 28.6% and 3.9% increases in PL compared with the control and hydropriming treatments, respectively (Fig. 4b). Fig. 5 shows that the control group, which did not receive any priming treatment, exhibited shorter plumule and root lengths, reflecting basic growth. Hydropriming-treated wheat seedlings displayed moderate PL and RL growths, indicating some improvement compared with their control counterparts. However, Si-primed seedlings demonstrated the most noticeable PL and RL increases, suggesting that Si boosts early plant growth by enhancing both shoot and root development.
Effects of Si on the SFW and SDW of Wheat
Si-based seed priming at varying concentrations and durations resulted in significant SFW increases, with the most pronounced effect observed at 0.25 mM after 8-h priming compared with that following control treatment (Fig. 6a). Si priming at 0.25 mM for 8 h increased SFW by 28% relative to the control. Seed priming with Si at different concentrations and durations significantly increased SDW, particularly at 0.5 mM for 8 h, compared with the control (Fig. 6b). The maximum SDW, 0.51 g, was recorded under 0.5 mM Si priming for 8 h, followed closely by 0.5 and 0.47 g at 6 and 4 h, respectively. Si priming at a concentration of 0.25 mM resulted in a 20% increase in SDW compared with the control, while that at 0.5 mM yielded a 19% increase (Fig. 6b).
Correlation analysis of wheat seed germination and seedling growth
A correlation matrix was developed to assess the impact of Si priming on germination and seedling growth parameters, revealing the effects of different exposure durations (4, 6, and 8 h ) on seed performance and development. At 4 h of Si priming, a strongly positive correlation was found between GP and GI (r = 0.96) as well as between VI and RL (r = 0.94) (Fig. 7). Moreover, at 6 h of Si priming, GP exhibited a strongly positive correlation with GI (r = 0.81), while GI also positively correlated with PL (r = 0.84). Similarly, VI displayed a strongly positive correlation with RL (r = 0.93) (Fig. 7). Finally, after 8 h of priming, positive associations also persisted between GP and GI (r = 0.89) as well as between VI and RL (r = 0.98). Further, VI and SFW (r = 0.84) as well as RL and SFW (r = 0.79) also exhibited positive correlations (Fig. 7).
DISCUSSION
Seed priming is an effective and widely used pre-sowing seed treatment that improves seed germination and seedling establishment by modulating various physiological and biochemical processes (Nawaz et al., 2013;Steven et al., 2024). This hydration technique enhances metabolic activities during the imbibition phase, preparing seeds for a more synchronized and rapid germination (Garcia et al., 2021). By controlling the hydration process, seed priming regulates key metabolic pathways, helping trigger early germination events, such as enhanced enzyme activity, improved energy metabolism, and growth-regulating substance synthesis (Farooq et al., 2019). The simplicity, cost-effectiveness, and efficacy of seed priming in increasing crop establishment, yield potential, and tolerance to diverse biotic and abiotic stresses render it an attractive technique for sustainable agriculture (Jisha et al., 2013). Seed germination is a complex physiological and biochemical process that marks the transition of a seed from dormancy to active growth (Bewley et al., 2013). It involves a series of tightly regulated stages, starting from water absorption (imbibition), metabolic pathway activation, and cellular activity resumption, leading to the emergence of the radicle (Nonogaki, 2014). Successful germination is crucial for crop establishment and serves as a foundational phase that determines seedling vigor, uniformity, and overall crop performance (Finch-Savage and Bassel, 2016) Therefore, this study focused on the application of Si as a potential priming agent to improve germination and seedling growth in wheat.
Si, a beneficial element, is known to enhance seedling vigor and provide tolerance to abiotic stresses by strengthening cell walls, increasing antioxidant activity, and promoting root and shoot elongation (Farooq et al., 2013). Moreover, it reportedly serves a central role in mitigating the effects of drought, salinity, and other environmental stresses by regulating water uptake and osmotic adjustment in plants (Bijanzadeh and Egan, 2018). In this study, the use of Si as a priming agent significantly improved key germination parameters, including GP, GI, and VI, as well as seedling growth parameters, such as RL, PL, SFW, and SDW. These findings are consistent with those of Hammami and Ahmed (2024), who highlighted that Si, when used as a priming agent, acts as an essential nutrient and a trigger for physiological processes, thereby improving seedling emergence and early seedling growth in wheat. Additionally, Wahid et al. (2008) reported that priming sunflower seeds enhanced radicle and plumule elongation, while Shehzad et al. (2012) found hydropriming to significantly improve sorghum seedling emergence and growth. Mridha et al. (2021) also demonstrated that Si priming in various crops resulted in superior seedling vigor, contributing to better establishment and resilience under adverse conditions.
Our study identified 1 mM Si and a priming duration of 6 h as optimal conditions for improving GP, GI, VI, RL, and PL in wheat. In another study, a similar concentration of Si (1 mM) significantly increased maize growth and grain yield under water-deficit stress (Sirisuntornlak et al., 2021). Furthermore, Ayed et al. (2021) demonstrated that priming wheat seeds with Si (15 mg/L) significantly increased GP, GI, shoot and root lengths, SFW, and VI. Additionally, Steven et al. (2024) reported that Si (0.5 mM) priming can increase the VI, hypocotyl growth, and RL of soybean compared with non-priming. These findings highlight that the optimal priming concentrations and durations may vary depending on species and environmental conditions. These treatments yielded superior germination and growth outcomes compared to the unprimed control. Notwithstanding, in certain cases, high Si concentrations were found to disrupt water and nutrient uptake, leading to an imbalance in nutrient status and reduced seedling performance (Liang et al., 2015). Therefore, identifying concentration thresholds beyond which priming agents may become detrimental to seed physiology is paramount. Further, the results revealed that Si concentrations of 0.25 and 0.5 mM significantly improved SFW and SDW compared with hydropriming treatments, suggesting that Si’s role in enhancing nutrient uptake, modulating antioxidant defenses, and improving the synthesis of growth-regulating substances (auxins and cytokinins) was more pronounced at lower concentrations (Hammami and Ahmed, 2024). These findings underscore the importance of carefully selecting priming concentrations and durations to optimize physiological benefits and avoid potential toxicity or imbalances in nutrient and water uptake. Si priming not only improves germination and growth but also enhances tolerance to high-alkaline stress (Liu et al., 2018).
Overall, this study corroborates the use of Si as an effective seed-priming agent for enhancing germination, seedling vigor, and overall growth in wheat. Its results demonstrate that when applied at appropriate concentrations and durations, this priming agent significantly improves early growth attributes, augmenting crop establishment and productivity. This aligns with the findings of Ali et al. (2021), Ellouzi et al. (2023), and Chen et al. (2023) who reported that Si priming not only boosts seedling vigor but also confers increased resilience to multiple environmental stresses. Ultimately, the selection of optimal priming conditions is requisite to maximizing seed physiological quality and performance, which, in turn, enhance the yield potential and adaptability of crops under diverse environmental conditions.
In future experiments, we aim to investigate the optimal silicon (Si) concentration of 1 mM and a priming duration of 6 hours to enhance wheat seedling growth under controlled greenhouse conditions. These parameters have been identified as promising in preliminary studies for improving germination rates and seedling vigor. Furthermore, we plan to evaluate the effectiveness of these Si treatments under salt stress conditions to address salinity, a critical constraint in wheat production. To gain a deeper understanding of the underlying mechanisms of salinity tolerance, we will analyze the expression of key genes associated with this trait in wheat. This comprehensive approach is expected to provide valuable insights into the physiological and molecular responses to Si priming, with implications for enhancing wheat resilience and productivity in saline environments.
적 요
종자프라이밍 기술은 종자의 발아율을 개선하는 데 효과적 인 것으로 알려져 있다. 본 연구는 밀 종자의 발아율과 초기 유묘 생장을 개선하기 위해, 다양한 농도의 규소를 사용하여 여러 시간 동안 종자프라이밍을 처리한 뒤 그 효과를 조사하 였다.
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본 연구에서는 처리구에 규소(sodium metasilicate pentahydrate (Na2SiO3ㆍ5H2O)를 0.25mM, 0.5mM, 0.75mM, 1.0mM 농 도로 희석하여 사용하였고, 대조구에는 증류수를 사용하였다.
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종자프라이밍은 4시간, 6시간, 8시간 동안 수행되었으며, 이후 종자의 발아율과 유묘 생육 특성을 조사하였다.
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실험결과 1.0mM의 규소를 6시간 동안 프라이밍 처리된 경우, Germination Percentage(GP), Germination Index(GI), Vigor Index(VI), Radicle Length(RL), Plumule Length(PL)가 각각 10.6%, 65.5%, 29.4%, 18.6%, 28.6% 증가하였다.
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본 연구는 1.0mM 농도의 규소를 6시간 동한 프라이밍하 는 조건이 밀 종자발아 및 유묘 생육 개선에 가장 효과적임을 시사한다.