Effect of bio priming agents on the germination of maize (Zee Mayz) under saline stress

Introduction

Globally, maize (Zea mays L.) is one of the most important cereal crops, serving as a staple food, industrial raw material, and livestock feed. In Nigeria, maize plays a critical role in food security, rural livelihoods, and agro-industrial development (Tahir et al., 2021; FAO, 2023) [5,13] . However, its productivity is increasingly threatened by abiotic stresses, particularly soil salinity. Salinity affects over 800 million hectares of land worldwide and continues to expand due to climate change, poor irrigation practices, and land degradation (FAO, 2023) [5] . Salt stress imposes both osmotic and ionic challenges on plants, limiting water uptake and causing toxic ion accumulation, which disrupts physiological and biochemical processes (Munns et al., 2020) [9] . These effects are particularly severe during seed germination and early seedling development.

Recent studies have further highlighted biochemical disruptions under salinity, including altered nitrogen metabolism and intracellular pH imbalance, which impair enzymatic activity during germination (Liu et al., 2024) [8] . However, recent studies confirm that plant-derived biostimulants improved stress tolerance and seedling growth under salinity conditions (Sharma et al., 2022; Singh & Kumar, 2023) [10,11] . Seed priming has emerged as an effective pre-sowing technique to improve germination performance under stress conditions. Bio-priming combining hydration with biological agents enhances seed performance by stimulating metabolic processes, improving antioxidant defenses, and promoting beneficial microbial interactions (Abbas et al., 2021; Bose et al., 2021) [1,3] . Despite increasing interest, there is limited research on locally available bio-priming agents such as ginger and Tithonia diversifolia in saline environments. This study therefore evaluated their effectiveness compared to Trichoderma.

Study area

The experiment was conducted in Biology Laboratory 2 at the University of Jos, located in Jos North Local Government Area, Plateau State, Nigeria, under controlled environmental Conditions. The study area is characterized by a tropical highland climate with average temperatures ranging from 18 °C to 30 °C. Recent studies have also illuminated the role of altered nitrogen metabolism in mediating salinity-induced germination inhibition. Liu et al. (2024) [8] reported that under salt stress, the hydrolysis of arginine-derived urea increases, resulting in the accumulation of hydroxide ions (OH⁻). This causes a rise in the cytoplasmic pH of seed cells, leading to alkalinity that disrupts enzyme function and metabolic homeostasis. Such biochemical disturbances at the cellular level further compound the detrimental effects of salinity on seed germination. -Enhances nutrient uptake.

-Improves germination under saline conditions. -Increases drought resistance.

Tithonia Extract Tithonia diversifolia

Phenolic compounds, alkaloids -Boosts antioxidant enzymes, improves nutrient uptake.

-Enhances growth in nutrient-poor soils. -Improves plant resistance to abiotic stress.

Onion Extract Allium cepa

Quercetin, sulfur compounds -Antioxidant and antifungal action.

-Enhances nutrient uptake and cell strength.

-Improves seedling growth and resistance to fungal diseases.

Nitrogen-fixing bacteria

Phytohormones, nitrogenfixing enzymes -Fixes atmospheric nitrogen in the soil.

-Produces plant growth-promoting hormones.

-Improves nutrient uptake and germination. -Enhances drought tolerance.

Bacillus subtilis Bacteria

Plant growth-promoting compounds, antifungal agents -Produces phytohormones and bioactive metabolites. -Suppresses pathogenic fungi.

-Improves growth under biotic stress.

-Increases seedling survival under salinity.

Rhizobium spp. (Microbe)

Nitrogen-fixing bacteria Nitrogen, phytohormones -Promotes root nodulation, nitrogen fixation.

-Enhances nitrogen availability to plants. -Improves early seedling establishment. [1,14,15,16,17]

Materials and Methods

Experimental design

A Completely Randomized Design (CRD) with factorial arrangement: Priming treatments: Control, ginger extract (5 g, 10 g, 15 g), Tithonia extract (5 g, 10 g, 15 g), Trichoderma. Salinity levels: 0, 50, 100 mM NaCl, Replications were 3 Total experimental units: 27

Seed preparation and priming

Seeds were surface-sterilized using 1% sodium hypochlorite and rinsed thoroughly. Bio-priming was conducted by soaking seeds in respective solutions for 4 hours.

Germination procedure

Seeds were placed in Petri dishes lined with Whatman filter paper and treated with respective NaCl solutions. Observations were recorded over 7 days.

Parameters measured

Germination Percentage (GP) Germination Rate (GR) Mean Germination Time (MGT) Seedling Vigor Index (SVI) Root Length Shoot Length

Statistical analysis

Data were analyzed using two-way ANOVA at p≤0.05.

Results

the effect of bio-priming agents and salinity stress on the germination percentage of maize seeds is presented in Table 2 showing the two-way ANOVA which revealed that neither biopriming treatments nor salinity levels had a significant effect on germination percentage (p>0.05). This means that, regardless of the priming agent used or the salt concentration applied, the proportion of maize seeds that successfully germinated remained relatively similar. Although some variation was observed among treatments, the differences were not strong enough to be statistically meaningful. This suggests that maize seeds have a relatively stable germination capacity even under moderate salinity stress. This implies that the bio-priming agents and varying salinity concentrations did not significantly affect the ability of maize seeds to germinate. Although differences exist among treatments and observation days, they were not statistically significant (P>0.05). This indicates that while priming influenced germination percentage, variation among replicates was high. Table 3 revealed that there was no significant effect (p>0.05) of priming treatments or salinity on the mean germination time of maize seeds. In other words, the speed of germination did not vary much across treatments. The variations are due to chance rather than factors tested as the F calculated (2.996 and 3.885) were greater than the treatment and column 0.82 and 0.39 respectively). This was similarly observed for p values which were above 0.05 On Table 6, priming treatments (0.0069) and salinity significantly (0.00007) affected root length (p<0.05). Bioprimed seeds developed longer roots compared to the unprimed control, while higher salinity levels sharply reduced root elongation. This showed the protective role of bio-priming in supporting stronger root systems under saline conditions. Biopriming enhanced root elongation under salinity stress, while increasing salinity reduced root growth. Shoot length was also significantly (0.0012 and 0.0028 respectively) influenced by priming and salinity as p<0.05. Primed seeds produced taller shoots than the unprimed control, while salinity consistently reduced shoot growth. This suggests that priming not only strengthens the root system but also promotes shoot elongation, while salinity inhibits shoot expansion. Primed seeds produced longer shoots compared to the control, while higher salinity reduced shoot elongation.

Discussion

the results of this study revealed that bio-priming agents exhibited differential effects on maize germination and seedling growth under salinity stress. Bio-priming treatments (Ginger, Tithonia, and Trichoderma) did not significantly improve final germination percentage or mean germination time when compared to the control. This suggests that maize seeds inherently possess strong germination capacity, and moderate salinity levels (as used in this experiment) did not drastically inhibit germination. Both ginger and Tithonia slightly enhanced germination uniformity compared to the control, though not significantly. Trichoderma also maintained similar germination percentages, indicating that the major benefits of bio-priming become evident beyond the early germination phase. Additionally, this indicates that priming agents did not accelerate the germination process, and moderate salinity stress also did not cause noticeable delays. This agrees with Kaya et al. (2018) [7] , who found that priming has a limited influence on germination speed unless salinity is extreme. This suggests that the speed of germination was not influenced by bio-priming agents or salinity stress. According to Kaya et al. (2018) [7] , germination time is often less responsive to priming under moderate salt conditions. Unlike germination percentage, salinity significantly reduced germination rate. Seeds in higher salt concentrations took longer to sprout. Among priming agents, Trichoderma-primed seeds exhibited a comparatively higher rate of germination under saline conditions, likely due to improved water uptake and stress tolerance mechanisms mediated by the fungus. Ginger and Tithonia treatments produced intermediate results, while the control seeds were most affected. This suggests that bio-priming can mitigate the delay caused by salinity, with Trichoderma showing the strongest effect. This result highlights an important distinction: salinity may not stop seeds from germinating, but it can delay the process, which reduces uniformity of seedling emergence. This indicates that increasing salinity concentrations slowed the rate of germination. This result aligns with earlier reports that salt stress reduces water uptake and delays enzymatic activation necessary for germination (Jisha et al., 2019) [6] . Although SVI did not differ significantly across treatments, there was a clear downward trend with increased salinity. Ginger and Tithonia priming appeared to slightly improve seedling vigor relative to the control, possibly due to their phytochemical and nutrient contributions, though variation was high and not statistically significant. This aligns with reports by Singh et al. (2021) [17] , who noted that vigor indices are often suppressed under salinity but can be improved through biochemical enhancement. These trends suggested that higher salinity lowered seedling vigor, suggesting that seed vigor was not markedly influenced by either priming treatments or salinity levels. However, vigor index is often affected under prolonged salinity, where metabolic damage accumulates (Singh et al., 2021) [17] . Both salinity and priming significantly influenced root growth. Trichoderma-primed seeds consistently produced longer roots than other treatments, highlighting its role in root system development under stress. Trichoderma is known to release plant growth hormones such as Indole-3-Acetic Acid (IAA), which promote root elongation and branching, thereby improving water and nutrient acquisition in saline soils (Afzal et al., 2021) [2] . Tithonia extract also improved root growth, probably due to its mineral content and organic compounds that stimulate metabolic activity. Ginger priming showed moderate improvement, likely linked to antioxidant compounds that mitigate oxidative stress in root tissues. The control (water-primed) seeds had the shortest roots under saline conditions. This agrees with reports that seed priming improves root system architecture and nutrient uptake under saline environments (Bose et al., 2021) [3] . Shoot length was significantly affected by both priming and salinity. Ginger-primed seeds (especially at higher concentrations) recorded better shoot elongation compared to the control, suggesting that ginger bio-actives (gingerols, antioxidants) may enhance cell expansion under saline stress. Trichoderma priming also significantly improved shoot growth, corroborating its known role in stimulating systemic tolerance and nutrient efficiency (Farooq et al., 2017) [4] . Similar results were reported by Farooq et al. (2017) [4] , who found that seed priming improved shoot growth by enhancing stress tolerance and osmotic balance under saline conditions. Tithonia extract had a positive but less pronounced effect on shoot elongation, likely due to its nutrient-enhancing properties. In contrast, control seedlings exhibited the shortest shoots, highlighting the beneficial role of bio-priming in alleviating saltinduced shoot inhibition. Overall, while germination percentage and Mean Germination Time (MGT) were not significantly influenced, germination rate, root length, and shoot length responded strongly to both salinity and priming treatments. Trichoderma emerged as the most effective priming agent, followed by ginger and Tithonia, in supporting seedling establishment under saline conditions. This demonstrates that the advantage of bio-priming lies not in ensuring seeds germinate but in enhancing seedling vigor and early growth under stress conditions. These results confirm earlier reports (Jisha et al., 2019; Bose et al., 2021) [3,6] that seed priming enhances tolerance to abiotic stress by activating defense pathways, improving osmotic regulation, and stimulating antioxidant systems. The practical implication is that farmers in saline-prone areas can benefit more from bio-priming when targeting strong seedling establishment rather than germination initiation.

Conclusion

Bio-priming did not significantly influence germination percentage or MGT but significantly improved root and shoot growth under saline conditions. Trichoderma was the most effective priming agent, followed by ginger and Tithonia extracts. Bio-priming is therefore recommended as a sustainable, lowcost, and eco-friendly strategy for enhancing maize establishment in saline-prone soils.

Recommendations

References

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