Planting  

The planting date was November 1, 2022. The pot experiment was carried out at Wasit's greenhouse before being grown in compartmentalized containers filled with (Van Egmond) peat moss, which has a high concentration of vital components, a pH of 6.4, and an electrical conductivity between (1.2 and 1.6). It was split into three sections, each of which had fifteen panels. There were 75 panels in all, each containing ten seeds.

Treatments

The seeds were coated with Nano Titanium dioxide at concentrations of (0,100,200,300, and 400) ppm and nano-selenium at concentrations of (0,20,40,60, and 80) ppm. Nano titanium dioxide and nano-selenium were obtained from Baghdad, Bab al-Muadham.

Growth characteristics

After 25 days of seed coating, the average shoot length cm, the number of leaves per plant, and the protein content were evaluated using the micro-Kjeldahl technique developed by [7]. Carbohydrates were assessed calorimetrically using the [8] technique. Antioxidant activity % was evaluated using the method described [9].

Statistical analysis

To investigate how statistically various treatments differed, the Randomized Complete Block Design (RCBD) analysis of variance test was utilized. Discovering discrepancies between means, analysis of variance and least significant difference were calculated. The level of statistical significance was set at > 0.05 [10].  

Results

The performance evaluation of the suggested (PMDC) involved comprehensive assessments of its functionality. Three key parameters were analyzed: organic content removal from raw sewage, total dissolved solids (TDS) elimination from saline water, and power generation. Fig.2 presents the profiles of organic content removal efficiency as (COD) in raw sewage, TDS elimination efficiency in saline water, and power generation.

The PMDC had a COD removal efficiency of 93±3%, suggesting its effectiveness in lowering organic content in raw sewage. The PMDC eliminated TDS with 70±4% efficiency, making it a feasible choice for saline water treatment. Moreover, the PMDC system exhibited remarkable power generation capabilities, generating an average of 24.3±2.5 mW/m³, which adds to its practical uses.

In addition, the study investigated the characterization of bacterial colonies in the anode biofilm before (G1) and after (G2) PMDC operation.

Molecular identification revealed 13 new strains in the initial biofilm (G1) and 6 new strains in the developing biofilm (G2), as shown in Table 1. These strains fell into several groups, such as cocci, gram-negative rods, and coccobacilli. Two prominent bacteria in the PMDC system, Escherichia coli and Staphylococcus haemolyticus, are noteworthy for their persistence in both biofilm stages.

The results of characterization confirmed the existence of 13 and 6 new strains in the anodic biofilm before and after the PMDC operation was shown respectively in Table 1.

Additionally, the study explored the kinetics of microorganisms' growth in the anode biofilm. ATP (adenosine triphosphate) was monitored at predetermined intervals, and it was observed that ATP increased as COD decreased, indicating an inverse relationship between substrate consumption and microorganisms' growth (Fig.3).

Furthermore, five alternative kinetic models were used to estimate the specific growth rate of mixed bacterial cells (Fig. 4). The Monod model, characterized by a maximum specific growth rate (µ_max) of 6.094 per hour and a half-saturation constant (K_s) of 630 mg/L, demonstrates a good fit with an R-squared (R²) value of 0.951. Similarly, the Blackman model exhibits a µmax of 6.283 per hour and a K_s of 313.7 mg/L, achieving an R² of 0.907. The Tessier model, with a µmax of 6.725 per hour and a K_s of 350 mg/L, shows an R² of 0.854. The Moser model, more complex with additional parameters, including empirical constant (m) with a value of 0.978, has a µmax of 7.102 per hour and a K_s of 480 mg/L, yielding an R² of 0.865. Lastly, the Han-Levenspiel model, indicating empirical constant (n = 1, m = 1.1055) and a threshold substrate concentration (S_m) of 750 mg/L, has a µmax of 6.998 per hour and a K_s of 430 mg/L, but notably, it exhibits a lower R² value of 0.221, suggesting a less accurate fit compared to the other models.

Figures & Tables

Discussion

Average Plant Height

Table 1 indicates that Nano Titanium dioxide has a significant impact on average plant height. When the nano titanium dioxide concentration was raised from 100 ppm to 400 ppm, the mean height of the plants reached consistently from 29.462 to 35.051 cm. Plants treated with 400 ppm nano titanium dioxide grew the fastest. The nano-selenium also had a substantial impact on the average plant height. Similarly, when the concentration of nano-selenium increased, it also increased the average plant height. Compared to 20 ppm (29.384cm) and the control (26.679cm), 80 ppm of nano-selenium produced the largest plants (34.949cm).

There was a substantial interaction impact between nano titanium dioxide and nano-selenium (see Table 1). Plants coated with 400 ppm nano titanium dioxide and 80 ppm nano-selenium grew the tallest.

Average number of leaves per plant

Table 2 suggests that Nano Titanium dioxide had a significant impact on the average number of leaves per plant. When the nano titanium dioxide concentration grew from 100 ppm to 400 ppm, the mean height of the plants reached consistently from 15.759 to 21.661 leaves per plant. Plants treated with 400 ppm nano titanium dioxide produced more leaves per plant. Nano-selenium also had a substantial impact on the average number of leaves per plant.

Similarly, when the quantity of nano-selenium increased, so did the average number of leaves per plant. In comparison to 20 ppm (18.773) and the control (16.330), 80 ppm of nano-selenium produced 27.293 leaves per plant.

There was a significant interaction impact between nano titanium dioxide and nano-selenium (see Table 2). The plants with 400 ppm nano titanium dioxide and 80 ppm nano-selenium had the most leaves (27.293).

Table 3 demonstrates that Nano Titanium dioxide has a significant effect on carbohydrates. When the nano titanium dioxide concentration was raised from 100 ppm to 400 ppm, the mean carbohydrate climbed progressively from 51.205% to 58.722%. Plants exposed to 400 ppm nano titanium dioxide grew glucose. The micro selenium also had a substantial impact on the average carbohydrate. Similarly, when the concentration of nano-selenium increased, so did the average carbohydrate. Compared to 20 ppm (50.187%) and the control (47.973%), 80 ppm of nano-selenium produced carbohydrate (58.413%). Table 3 shows that the interaction impact between nano titanium dioxide and nano-selenium was considerable. Carbohydrates content in seeds coated with 400 ppm nano titanium dioxide and 80 ppm nano-selenium (66.027%) were the most common.

Average Protein

Table 4 demonstrates that Nano Titanium dioxide has a significant effect on protein. When the nano titanium dioxide concentration was raised from 100 ppm to 400 ppm, the mean protein rose consistently from 31.497% to 37.963%. Plants treated with 400 ppm nano titanium dioxide produced protein. The micro selenium also had a substantial impact on the average protein content. Similarly, when the quantity of nano-selenium increased, so did the average protein content. In comparison to 20 ppm (31.509%) and the control (29.577%), 80 ppm of nano-selenium  produced an  average protein content of 37.169%. Table 4 shows that the interaction impact between nano titanium dioxide and nano-selenium was considerable. The protein content (43.810%) was  observed in seeds coated with 400 ppm nano titanium dioxide and 80 ppm nano-selenium .

Average Antioxidant activity

Table 5 shows that Nano Titanium dioxide has a significant impact on antioxidant activity. When the nano titanium dioxide concentration was raised from 100 ppm to 400 ppm, the mean antioxidant activity rose consistently from 27.729% to 36.017%. Plants treated with 400 ppm nano titanium dioxide developed antioxidant activity. Nano-selenium also had a substantial impact on overall antioxidant activity. Similarly, when the quantity of nano-selenium increased, so did the average antioxidant activity.

In comparison to 20 ppm (29.801%) and the control (27.691%), 80 ppm of nano-selenium produced 35.181% antioxidant activity. Table 8 shows that the interaction impact between nano titanium dioxide and nano-selenium was considerable. Those covered with 400 ppm nano titanium dioxide and 80 ppm of nano-selenium had the highest antioxidant activity  (41.180%).

Discussion

Plant physiological properties were favorably influenced by seed coating with (Titanium dioxide and Selenium) nanoparticles (Table1,2). Based on the results of TiO₂ NPs’ effect on seed germination and early seedling growth, it is possible that NPs aided in seed water absorption, increased seed ability  to  absorb and utilize water efficiently, and activated and promoted hydrolytic enzymes in the seed antioxidant system [11].

TiO₂ NPs absorption via roots result in increased root and shoot length as well as root and shoot fresh weight in seedlings. The uptake of nanoparticles across the cell wall is primarily determined by particle size and cell wall pores. Because of the tiny diameter of TiO₂ NPs, these nanoparticles may enter plant roots through cell wall pores. As previously shown, smaller NPs with greater surface reactivity may widen or generate new root pores, resulting in increased hydromineral movement in roots. As a result, the increased root length is due to enhanced nutrient intake, increasing  shoot and root length as well [12]. TiO₂ NPs stimulated both shoot and root development in seedlings, with shoot growth being more prominent than root growth. Gibberellins (GAs) are known to promote shoot development, therefore photocatalytic TiO₂ NP supplements may have increased GA levels. The shoots will develop into leaves, which will be the primary portion consumed by consumers of these green vegetables. NP supplementation might be a novel approach to improve  the development of economically important agricultural plants [13]. Priming with TiO₂ NPs has been shown to improve seed germination (SG) and seedling growth. This might be owing to the rapid completion of metabolic activities during the pre-germination stage during the priming phase, which resulted in increased SG levels and greater seedling growth levels. TiO₂ increased SG and promoted radicle and plumule development in plant seedlings [14].

Plants benefit from selenium nanoparticles by protecting the shape and fluidity of chloroplast and plasma membranes, activating membrane enzymes, transferring metabolites in chloroplasts, boosting photosynthetic activity, delaying aging, and increasing plant yield [15]. Selenium  is  the principal component of many selenium-containing enzymes that may be identified by improving the morpho-functional properties of seeds and young plants, this  compound is  non-toxic and regulate metabolic processes [16]. It had an advantageous influence (Table 3,4,5) on the seed coating with (Titanium dioxide and Selenium) nanoparticles affecting  active chemicals and oxidizing enzymes.  Because of its hydrophilic nature, exogenous application of Se NPs to carrot plants increased total soluble carbohydrates, soluble protein, and proline, which is extremely sensitive to environmental stresses and controls the numerous genes involved in growth and metabolism by providing energy resources and carbon [17]. The impacts of Se NPs preparation and looking into the effects of Se NPs on the germination characteristics of other popular crops including maize, rice, and soybeans. Se NPs enhance root growth and organogenesis as well. Trace amounts of Se have been demonstrated to enhance growth in lettuce, ryegrass, Brassica oleracea, and potato plants [18]. Se NPs improve photosynthesis by protecting chloroplast enzymes and protecting the chloroplast structure from severe oxidative damage, such as the loss of grana and stromal lamellae. According to research, Se speeds up chlorophyll formation by facilitating respiration and electron transfer in the respiratory chain. It is possible that enhanced biomass after seed priming is due to Se NPs mediated greater photosynthesis in plants under both studied watering regimes [19].

According to the results of the previously mentioned study, seed coating fenugreek (Trigonella foenum graecum L.) with nano-titanium dioxide and nano-selenium to the plant significantly increased all traits, regardless of whether the characteristics of vegetable or antioxidant activity achieved the highest concentrations used the highest effects, whether alone or in combination with two other compounds.

Conflict of Interest

The author declare that there is no conflict of interest regarding the publication of this paper.

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