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Article

Coatings Applied to the Optimization of Portulaca oleracea L. Seed Pellet Formulation Based on Mixture Design

by
Jinhua Sun
1,2,†,
Fen Liu
2,†,
Yanqin Xu
1,* and
Weiming Hu
2,3,*
1
College of Pharmacy, Jiangxi University of Chinese Medicine, Nanchang 330004, China
2
Jiangxi Provincial Key Laboratory of Plant Germplasm Resources Innovation and Genetic Improvement, Lushan Botanical Garden, Jiangxi Province and Chinese Academy of Sciences, Jiujiang 332900, China
3
Jiangxi Academy of Forestry, Nanchang 330032, China
*
Authors to whom correspondence should be addressed.
†
These authors contributed equally to this work.
Coatings 2025, 15(3), 341; https://doi.org/10.3390/coatings15030341
Submission received: 1 February 2025 / Revised: 10 March 2025 / Accepted: 14 March 2025 / Published: 15 March 2025
(This article belongs to the Section Coatings for Food Technology and System)
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Versions Notes

Abstract

:
Portulaca oleracea L. is an important herb with the same origin in medicine and food. To achieve the precise sowing of P. oleracea, this study employed a mixed experimental design to optimize the pellet formulation of the seeds. Fillers such as kaolin, bentonite, and talcum powder were used, along with binders including polyvinyl alcohol, sodium alginate, and sodium carboxymethyl cellulose. The physical characteristics and germination properties of the pelletized seeds were evaluated to determine the optimal formulation. The results indicated that, after pelletizing, the seeds exhibited a higher seed viability and vigor, germination rate, and germination index. Specifically, the seed singulation rate correlated positively with the kaolin content, the disintegration rate was proportional to the amount of talcum powder added, and the compression resistance was positively correlated with the bentonite ratio. Using response optimization, the optimal formulation of fillers used for pelletizing P. oleracea seeds was identified as 17% talcum powder, 16% kaolin, and 67% bentonite. Single-factor experiments showed that using PVP as a binder at a mass fraction of 10% resulted in improved pelletizing indices. This study not only optimized the pelletizing formulation of P. oleracea seeds based on physical and germination properties, but also expanded the application of pelletizing in the processing of the seeds of traditional Chinese herbs. It holds significant implications for the mechanized production of small, pelletized seeds of traditional Chinese herbs.

1. Introduction

Portulaca oleracea L., belonging to the family Portulaca, is an annual herbaceous plant known as grass jelly or mustard greens [1]. It is widely distributed in tropical and subtropical regions and exhibits strong resilience to various abiotic stresses, including light intensity, temperature, humidity, and soil types [2,3], employing both C4 and CAM photosynthetic pathways [4]. The dried parts of the plant above the ground of P. oleracea was used in traditional Chinese medicine over 2000 years. It exhibits therapeutic properties including heat-clearing and detoxification, blood-cooling hemostasis, and dysentery-relieving effects. Clinically, it is indicated for the treatment of suppurative infections (carbuncles, furuncles, and sores), hematochezia, hemorrhoidal bleeding, venomous bites, and eczematous dermatoses [5]. Phytochemical studies have revealed that P. oleracea is rich in omega-3 and omega-6 fatty acids, ascorbic acid (Vitamin C), glutathione, and β-carotene [6,7,8], rendering it highly nutritious with significant health benefits. Recognized by health authorities, it is listed as both a food and medicinal product [9]. Additionally, it contains flavonoids [10], polysaccharides [11], alkaloids, and other active ingredients [12], exhibiting pharmacological properties such as antimicrobial [13], antioxidant [14], anticancer [15,16,17], and hypoglycemic effects [18]. P. oleracea’s high content of vitamins E and C contributes to its use in skincare and cosmetics products [19,20,21,22]. Moreover, experimental evidence supports its ability to remediate soil contaminants [23], which can be used to detect heavy metals in the soil and perform ecological environment remediation [24].
Currently, the cultivation of P. oleracea involves sexual and asexual reproduction, primarily through seed propagation [25]. Under scanning electron microscopy, the seeds of Portulaca oleracea exhibited a broadly obovate-reniform morphology. The hilar region was characterized by a distinct concave structure formed at the junction between seed coat components, and also revealed that the hilum was enveloped by a specialized membrane demonstrating a unique combination of structural features: a loose, loofah-like porous framework intergrading with membranous tissue exhibiting butterfly-wing morphology [26]. However, the small seed size, light weight, and uneven seed morphology of P. oleracea hinder precise sowing using traditional broadcasting methods. As the best way to resolve this problem, seed pelleting can increase the volume and weight of seeds [27,28], meeting the demands of modern agriculture and enabling precise sowing with accurate depth and spacing, uniform coverage, an optimal planting speed, and improved planting efficiency. Seed pelleting involves wrapping the surface of the seeds with pelleted coatings through a pelletizer, creating a protective layer on the seed surface that enhances hardness and permeability. The pelleting of seeds has also been shown to enhance germination rates and seed viability [29,30,31], and facilitates the incorporation of nutrients, pesticides, and plant growth regulators [32]. Seed pellet granulation coatings are mainly divided into fillers and binders. The main fillers used are talc [33], bentonite [34], kaolin [35], diatomaceous earth [36] and activated carbon [37]. There are three types of binder: inorganic binders, organic binders and composite binders [38]. The binders primarily used in pelleting coatings are carboxymethylcellulose sodium [38], sodium alginate [39], polyethylene glycol [40], magnesium stearate [41] and peach gum powder [42].
While research on seed pelleting has focused mainly on vegetables, flowers, and staple crops, studies on the pelletizing of Traditional Chinese Medicine (TCM) seeds and the achievement of precise TCM sowing remain limited [28,43]. With an increase in health awareness and the demand for medicinal herbs, particularly those that can be consumed and be used in medicines, the cultivation area of TCM herbs in China continues to expand [44]. The irregular seed shape and small size of most TCM species pose challenges to large-scale mechanized planting. Therefore, this study investigates the influence of different filler ratios and types/concentrations of binders on the pelletization performance of P. oleracea seed in order to optimize pelleting formulations. The findings provide a theoretical basis for pelletizing various types of TCM seeds and the precise mechanized planting of medicinal herbs.

2. Materials and Methods

2.1. Experimental Materials

The experimental materials used in this study included P. oleracea L. seeds sourced from Xuzhou Lincao Sales Store. The fillers used were talcum powder, kaolin, and bentonite. The binding agents consisted of polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethylcellulose sodium (CMC-Na). The equipment utilized comprised a CNC seed-coating machine (Qingdao Huiyinong Agricultural Technology Co., Qingdao, China), a DF multi-wing low-noise centrifugal fan (Qingdao Huiyinong Agricultural Technology Co.), circular sieves with pore sizes of 1.5 mm, 2 mm, 2.5 mm, and 3 mm, and an electronic scale, Digital Push-Pull Gauge (−500, WDGAGE).

2.2. Experimental Design

A mixture experimental design was employed, with the upper and lower limits of the three fillers set at 0% and 100%, respectively, under the assumption that the sum of the talcum powder, kaolin, and bentonite equaled 100%. Using Minitab 21 software, a mixture design yielded a total of 21 formulations (Table 1). The binder formulation used the optimal ratios obtained from the filler experiments as the basis for subsequent binder experiments, which were conducted as single-factor experiments. The binder ratios were set to N1 (5% PVP), N2 (10% PVP), N3 (20% PVP), N4 (5% SA), N5 (10% SA), N6 (20% SA), N7 (5% CMC-Na), N8 (10% CMC-Na), and N9 (20% CMC-Na).
Fifteen grams of uniformly sized P. oleracea seeds was weighed and placed into the coating machine (HynE-wlhj seed pelletizing machine). An appropriate amount of distilled water was added to moisten the seeds’ surface. The coating machine was operated at 40 revolutions per minute (rpm) after achieving a state in which the seeds clumped upon pinching and scattered upon touching. The pre-prepared granulation reagent was sprayed into the coating machine after each powder was added, ensuring that each seed was evenly covered. Once the coating agent became clear, a second round of distilled water was added; the granulation reagent was then applied again once the seed surfaces were moistened. Throughout this process, seeds forming clumps were removed using a sieve with a diameter of 2 mm. This cycle continued until all 300 g of granulation reagent was uniformly coated on the seed surface, retaining seeds sized between 2.5 mm and 3 mm. Subsequently, distilled water was added to lightly moisten the seed surfaces. The machine was then operated without filling for 5 min to achieve smooth and uniform seed surfaces, enhancing the strength and compactness of the seed surface. Finally, the granulated seeds were transferred to a drying machine (Qingdao Huiyinong Agricultural Technology Co.) and dried until a constant weight was achieved.
The physical properties of the granulated seeds (seed rate, single grain rate, disintegration rate, compressive strength) and germination properties (germination potential, germination rate, germination index) were used as response values in order to select the optimal mixture design.

2.3. Physical Shape of Pellet Granulated Seeds of Portulaca oleracea

Seeded rate and single seed rate: Fifty uniformly sized granulated Portulaca seeds were randomly selected and crushed. The number of granules containing Portulaca seeds was recorded and expressed as a percentage of the total granules in order to define the seed rate. Additionally, the number of granules containing only one purslane seed was recorded and expressed as a percentage of the total granules in order to define the single grain rate.
Disintegration rate [41]: Fifty uniformly sized granulated Portulaca seeds were placed on double-layered moist filter paper in a Petri dish and uniformly sprayed with 5 mL of water. The number of seeds that disintegrated within 5 min was recorded as a percentage of the total seeds. This process was repeated three times, and the average value was calculated.
Compressive strength [41]: The maximum pressure at which granulated Portulaca seeds fractured was measured using a push–pull gauge. This test was repeated 10 times, and the average value was calculated.

2.4. Germination Index of Pelletized Seeds

In this experiment, the germination potential and germination rate were determined using a paper-based germination test [41]. Fifty granulated Portulaca seeds were randomly placed on two layers of moist filter paper in a 9 cm diameter Petri dish. Five milliliters of water was added to keep the filter paper moist. The dishes were then placed in a constant temperature and light incubator. The number of germinated granulated seeds was recorded daily for 7 days.
Germination potential = total number of seeds germinated in the first 3 days/number of seeds supplied.
Germination percentage = total number of seeds germinated on the 7th day/number of seeds supplied for testing.
Germination index = ∑(Gt/Dt), where Gt is the number of seeds that had germinated normally on day t and Dt is the number of corresponding germination days.

2.5. Data Processing

Experimental data were organized and analyzed using Excel 2021 for data management, as were the correlation between the type of filler and the physical and germination indexes, as well as the correlation between the concentration of each binder and the germination indexes. Minitab 21 was used to optimize the response of the physical and germination parameters of the seeds after granulation with fillers to obtain the optimum filler ratio. The one-way-ANOVA in GraphPad Prism 9.0.0 was used to compare the differences in seed germination performance between pelletized seeds with different filler ratios and the blank group, and plotted using GraphPad Prism 9.0.0. Correlation analysis and graphical representation of seeds after pelletization with three binders and physical parameters of pelletised seeds were carried out using OriginPro 2024.

3. Results

3.1. Impact of Different Filler Ratios on the Physical Properties of Granulated P. oleracea Seeds

The diameter of the P. oleracea seeds was initially only ~1.5 mm, which posed challenges to precise mechanical sowing. Therefore, the size and shape of the granulated seeds post-coating were used to evaluate the granulation process. All fillers enabled P. oleracea seeds to form granules, resulting in significant changes in the shape and size of the seeds compared to non-granulated seeds (Figure 1). Using sieves, it was found that the size of the granulated seeds from all 21 filler ratios ranged from 2.50 mm to 3.00 mm, although the improvement in appearance varied among different filler ratios.
Different fillers exhibited varying effects on the physical properties of granulated seeds (Figure 2). All granulated P. oleracea seeds achieved a seed rate exceeding 95%, meeting the general quality requirements for granulated seeds. Groups 2, 3, 4, 5, and 20 had single grain rates below 90%, with Group 5 showing the lowest single grain rate. This reduction was attributed to an increase in the proportion of bentonite, which increased the viscosity after moistening; this potentially caused the seeds to adhere and form multi-seed granules, thereby lowering the single grain rate.
Groups 3, 6, and 15 exhibited disintegration rates below 80%, while the rest of the filler groups had rates exceeding 80%, meeting the typical quality standards for granulated seeds. Among the 21 filler formulations, the group composed of 60% talcum powder, 20% kaolin, and 20% bentonite exhibited the highest disintegration rate after granulation. As the content of talcum powder increased, the disintegration rate also increased.
In terms of the compressive strength, every filler ratio group exhibited high values exceeding 1.47 N after granulation, meeting the general quality requirements for granulated seeds. An analysis of the compressive strength of granulated seeds from the 21 filler formulations indicated that increasing the bentonite content enhanced the compressive strength (Figure 2). Groups 7, 10, 13, and 21 exhibited notably higher compressive strength values and significantly surpassed other groups, with these groups having a higher proportion of bentonite compared to other fillers.

3.2. Impact of Different Filler Ratios on Seed Germination Performance

After pelletization, the germination potential and rate of P. oleracea seeds were over 90% in all groups, with a high germination index observed (Figure 3). One-way ANOVA analysis showed that pelletized seeds prepared with 21 distinct filler formulations exhibited significant differences in germination potential compared to the control group (n = 3, p < 0.05), whereas no statistically significant variations were observed in germination percentage or germination index. In the inter-comparison of the 21 treatment groups, there was no significant difference in any of the three indices. However, when compared with the control group, only groups 2 and 8 showed higher germination potential, and groups 2, 3, 8, 9, 11, and 21 showed higher germination rates. The remaining groups exhibited slightly lower germination potential and rates compared to the control, indicating that pelletized formulations may hinder seed germination to some extent. The increase in the proportion of talc powder corresponded with a higher germination potential, rate, and index for pelletized P. oleracea seeds. This relationship is likely due to talc powder’s excellent dispersibility at higher proportions, enhancing the pellets’ disintegration during seed germination and improving aeration. Additionally, the fillers in the pellets retain water, which aids in the germination of seeds.

3.3. Correlation Analysis Between the Proportion of Filler, the Physical Shape, and the Germination Shape of Pelletized Seeds

An analysis of the correlation between the proportion of filler and the physical characteristics of pelletized P. oleracea seeds (Figure 4A) revealed positive correlations between the proportion of talc powder and the seed viability and disintegration rate, however, it revealed negative correlations with the single pellet rate and compression resistance. The proportion of kaolin positively correlated with the single pellet rate, germination potential, and index, but negatively correlated with the viability, disintegration rate, compression resistance, and germination rate. Meanwhile, the proportion of bentonite positively correlated with the compression resistance, germination potential, rate and index, but negatively correlated with the viability, single pellet rate and disintegration rate.
The optimum ratio of fillers for the pellet granulation of P. oleracea seeds was found to be 17% talc, 16% kaolin and 67% bentonite; this was determined using Response Optimizer via Minitab 21 software and employing the physical and germination properties of each group of filler ratios as an indicator. At this ratio, using 10% PVA as a binder, the pill granulated seeds of P. oleracea had a 100% seeding rate, a 94.22% single seeding rate, a 97.33% disintegration rate, a 9.032 N compression resistance, a 97.33% germination potential, a 98% germination rate, and a 46.44 germination index, and the indicators of the sprouting properties were greater than those of the blank group. This proves that not only did this pill granulation formulation not impede the germination of P. oleracea, but it actually promoted germination.

3.4. Effects of Different Binders and Their Concentrations on the Physical Properties of Pellet Granulation

A further evaluation of the impact of different binding agents and their concentrations on the physical properties of pelletized P. oleracea seeds, based on the optimal filler ratio (17% talc powder, 16% kaolin, 67% bentonite), showed that pellets formed with different binding agents had different appearances (Figure 5). Using PVA solution as a binding agent results in rougher seed surfaces and more irregular shapes than the other agents. SA yields rough surfaces but more rounded or nearly round shapes, while CMC-Na provides smoother surfaces and regular, nearly round shapes.
The results obtained when evaluating the physical parameters of the seeds pelletized with different binding agents (Figure 6) show that all binding agents achieved viability rates exceeding 95% and a compression resistance exceeding 1.47 N; this meets the typical quality requirements for pelletized seeds. The seed disintegration rate decreased as the concentration of PVA and SA increased, whereas CMC-Na showed lower disintegration rates at both low and high concentrations. The single pellet rates decreased as the concentrations of PVA and CMC-Na increased, but remained higher with greater concentrations of SA.
The correlation coefficient graphs reveal that there were significant positive correlations between PVA (Figure 7A) and the compression resistance, and negative correlations with the disintegration rate and single pellet rate, and significant correlations with the seeded rate. SA (Figure 7B) showed positive correlations with the compression resistance and single pellet rate, and negative correlations with the disintegration rate, and significant correlations with the seeded rate. CMC-Na (Figure 7C) correlated positively with viability, and positively with the disintegration rate and compression resistance, meanwhile, it negatively correlated with the single pellet rate.

3.5. Impact of Different Binding Agents and Their Concentrations on Seed Germination Performance

The performance parameters related to the germination of pelletized seeds when using three different binding agents at varying concentrations were evaluated (Figure 8). As the concentration of the binding agent increased, the germination index of the pelletized seeds decreased. SA exhibited a significant inhibitory effect on the germination of seeds post pelletization, followed by CMC-Na, meanwhile, PVA showed minimal inhibition compared to the control group.
The results of the correlation analyses between the binding agent concentrations and germination parameters are presented in Figure 9. The PVP concentration was positively correlated with the germination potential and rate, but negatively correlated with the germination index. The SA concentration showed a positive correlation with the germination potential, and negative correlations with the germination rate and index. The CMC-Na concentration negatively correlated with the germination potential, rate, and index.
Based on the physical and germination performance parameters of seeds pelletized with three binding agents at varying concentrations, all agents successfully formed pellets from P. oleracea retroflexus seeds. In terms of the appearance of the seeds, the results were as follows: CMC-Na > SA > PVA. Meanwhile, in terms of the physical parameters, the results were as follows: CMC-Na > PVA > SA. Regarding the seed germination performance, the results were as follows: PVA > SA > CMC-Na. Despite differences in the physical parameters of the pellets formed using different binding agents, all met the general quality requirements for pelletized seeds. However, the seed germination performance is a critical indicator of seed quality, and pelletization should not compromise seed germination. Therefore, in this experiment, it was found that PVA should be used at a concentration of 10% for the pelletization of P. oleracea seeds.

4. Discussion

The mass and volume of P. oleracea seeds are very small, and their shape is oblate-oval, making mechanical sowing particularly challenging. Seed pelleting treatment significantly increases both the volume and weight of seeds, facilitating mechanical sowing implementation [45]. The earliest application of seed pelleting technology dates back to 1866 when wheat flour paste pellets were developed to improve cotton seed sowing [46]. Pelleted seeds enable precise seed spacing, reduce thinning requirements, and have been widely adopted for small-seeded crops including onions, lettuce, carrots, and tomatoes [47,48,49]. This technology also serves as an effective microbial inoculant delivery system, allowing beneficial microorganisms to be adhered to seed surfaces [50,51,52], thereby enhancing crop productivity, reducing agrochemical dependency, and revitalizing soil health [53,54].
As a long-established seed treatment method, pelleting technology requires customized formulations for different species. Previous studies have utilized bentonite, talc, and kaolin in coating applications, such as talc-bentonite combinations for tobacco seed pelleting [55,56]. Experiments demonstrating enhanced drought resistance in coated fennel seeds showed that vermiculite-perlite-kaolin coatings can improve both yield and stress tolerance [57]. Our study revealed that talc-, bentonite-, and kaolin-based pelleting of P. oleracea seeds enhanced germination potential while maintaining normal germination rates, consistent with previous research findings [32,58,59].
In accordance with general quality standards for the granulation of herbal seeds [60], a spherical and uniform shape, an appropriate size, and a smooth surface are typically required post-granulation. Specific parameters include the integrity of the seeds (≥95%), the single-seed rate (≥90%), the compressive strength (≥150 g) and the disintegration rate (≥98%); it should also be ensured that the germination of seeds is not compromised. In this experiment, some of the experimental groups did not meet the required seed integrity and single-seed rate. Correlation analyses between the filler proportions and seed integrity revealed that the proportion of talcum powder correlated positively with the seed integrity and as talcum powder content increased, disintegration rate also increased. Microscopically, talcum powder appeared as aggregates of blocky, flaky, and fibrous shapes [61], creating larger gaps after granulation that enhanced water absorption. Talcum powder also provided good lubrication and dispersion, contributing to higher disintegration rates as the content increased. Correlation analysis showed that the proportion of kaolin correlated positively with the single-seed rate. Several of the groups analysed for low disintegration rates had the highest percentage of kaolin. This phenomenon may be attributed to kaolin has the ability to increase the mechanical strength and improve the pore structure of cementitious materials [62], and the reduction in intermolecular distances of kaolin during the drying process, resulting in diminished void spaces within the pelletized structure. The consequent increased compactness among filler particles significantly reduced water absorption capacity of the pelleted seeds, ultimately leading to decreased disintegration efficiency. Correlation analysis showed that the proportion of bentonite correlated positively with the compressive strength, bentonite swells due to the penetration of water during granulation, compacting during drying to form a cohesive structure. All 21 granulated seed groups meeting the required compressive strength. Thus, practical considerations during production may involve adjusting the proportions of talcum powder and kaolin to ensure that the seed integrity and single-seed rate meet requirements.
Seed germination marks the beginning of plant development, with optimal sowing conditions required in order to achieve normal seed germination and the growth of robust seedlings, which is essential for high-yield cultivation [63]. The germination rate serves as a critical indicator of seed quality, reflecting the uniformity of seedling emergence to some extent. The germination index further indicates the vigor of seeds and their germination speed, providing insights into the overall performance of seeds during germination. It is clear from the mixed filler experiments and single-factor binder tests that the granulation of P. oleracea seeds does not adversely affect germination. Through oneway-ANOVA analysis of the differences between the germination indexes of the seeds after each filler ratio and those of the blank group, it can be seen that the germination potential of the seeds of the 21 groups of pelletised seeds were significantly different from those of the blank group, indicating that pelletisation can promote the germination of the seeds, which is conducive to the rapid germination of the seeds, thus reducing the hazards of the environmental changes on the germination of the seeds. The germination rate and germination index of the 21 groups of pelletised seeds were not significantly different from those of the blank group, which indicated that pelletisation did not inhibit seed germination and the physical and germination indexes were higher after pelletisation, therefore, the 21 groups of filler ratios can be used for the pelletisation of Portulaca spp. seeds in the actual production activities.
This experiment focused solely on the granulation of cultivated P. oleracea seeds, and showed that the use of different varieties might result in variations in granulation outcomes. The selected seeds exhibited relatively high germination rates, however, it was found that wild-type seeds might yield lower germination indices post-granulation due to their smaller size, potentially complicating the granulation process. Future research should explore wild-type Portulaca oleracea seeds, considering the possible decrease in germination indices and exploring the addition of plant growth regulators to granulation agents in order to promote seed germination. Studies [42] have observed improved seedling emergence rates and enhanced stress resistance in Panax seeds post-granulation, enhancing the quality of medicinal herbs. Larger seeds generally exhibit greater stress resistance post-granulation due to an increase in their volume and mass, forming a protective layer that enhances resistance [64]. This study focused on the physical and germination properties of granulated, however, further investigations are needed to assess the impact of granulation on the quality of medicinal herbs derived from Portulaca oleracea post-maturation.

5. Conclusions

This study investigated the effects of fillers and binders on the granulation of Portulaca oleracea seeds and evaluated the efficacy of granulation by assessing the physical and germination properties of the seeds post-granulation. The results indicate that fillers significantly influence the physical properties of granulated Portulaca oleracea seeds, with a minimal impact on germination. Among the fillers tested, the optimal composition was found to be 17% talcum powder, 16% kaolin, and 67% bentonite. Different binders exhibited varied effects on both the physical and germination properties of the granulated seeds, with 10% PVA identified as the optimal binder. The pelletized formulation developed in this study for Portulaca oleracea seeds demonstrated efficacy primarily in augmenting seed mass and volumetric dimensions, along with achieving morphological standardization. However, it exhibited limited capacity to enhance stress tolerance parameters and failed to provide supplementary nutrient supply during seed germination. Subsequent investigations should be conducted to optimize this coating matrix through compositional modifications, with particular emphasis on improving seed vigor indices.
This study focused on the irregular shape, small size and light weight of P. oleracea seeds and considered pelleting processing technology. This technological breakthrough resolves the mechanical precision seeding constraints in Portulaca oleracea cultivation caused by inadequate seed performance characteristics, thereby facilitating the convergence of its agricultural practices with modern mechanized cultivation systems. The innovation significantly reduces labor expenditure in traditional farming operations while establishing a scientific foundation for optimizing existing medicinal crop cultivation methodologies. Furthermore, it provides technical references for enhancing mechanization capacity throughout medicinal plant production processes. This study establishes a theoretical framework for optimizing Portulaca oleracea cultivation systems, while providing methodological guidance for enhancing stress tolerance mechanisms and refining agronomic practices under abiotic stress conditions.

Author Contributions

The authors confirm their contributions to this work: W.H. and Y.X. conceptualized the work; J.S. prepared the original draft and performed data analysis; J.S. and F.L. prepared the samples; and W.H., Y.X., and F.L. revised and reviewed the manuscript. All authors have read and agreed to the published version of the manuscript.

Funding

This work was supported by a grant from the Jiangxi Provincial Natural Science Foundation of China (20224BAB215002 to Fen Liu), the Jiangxi Provincial Introduced Intelligence Program (20212BCJ25024 to Fen Liu, 20212BCJ25025 to Weiming Hu), the Jiangxi Provincial International Science and Technology Cooperation Program (S2023KJHZH0040 to Fen Liu), the Jiujiang City “double hundred double thousand” talent project to Weiming Hu, the China Academy of Traditional Chinese Medicine Rare Traditional Chinese Medicine Resources Sustainable Utilization Capacity Building Project (2060302 to Weiming Hu), and the National Natural Science Foundation of China (32160099 to Weiming Hu).

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

Data sharing is available upon request.

Acknowledgments

We apologize to the authors whose works are not cited because of space limitations.

Conflicts of Interest

The authors declare no conflicts of interest.

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Figure 1. Seeds treated with 21 distinct filler formulations exhibited differential modifications in both size parameters and appearance.
Figure 1. Seeds treated with 21 distinct filler formulations exhibited differential modifications in both size parameters and appearance.
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Figure 2. The seeded rate, single seed rate, and disintegration rate (A) and compressive strength (B) of 21 groups. Data are represented as means ± SD of three biological replicates.
Figure 2. The seeded rate, single seed rate, and disintegration rate (A) and compressive strength (B) of 21 groups. Data are represented as means ± SD of three biological replicates.
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Figure 3. The germination potential (A) of each proportionate group was significantly different from that of the blank group. Asterisks indicate significant differences between the ratios and the blank group as revealed by one-way ANOVA analysis, * indicates p < 0.05, *** indicates p < 0.001, **** indicates p < 0.0001. There was no significant difference in germination percentage (B) and germination index (C) between the ratios and the blank group. Data are represented as means ± SD of three biological replicates.
Figure 3. The germination potential (A) of each proportionate group was significantly different from that of the blank group. Asterisks indicate significant differences between the ratios and the blank group as revealed by one-way ANOVA analysis, * indicates p < 0.05, *** indicates p < 0.001, **** indicates p < 0.0001. There was no significant difference in germination percentage (B) and germination index (C) between the ratios and the blank group. Data are represented as means ± SD of three biological replicates.
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Figure 4. Plot of correlation coefficients between three filler ratios and physical parameters and germination indicators of pelletized seeds. (A) Plotting of correlation coefficients between filler and physical indicators. (B) Plotting of correlation coefficients between filler and sprouting indicators.
Figure 4. Plot of correlation coefficients between three filler ratios and physical parameters and germination indicators of pelletized seeds. (A) Plotting of correlation coefficients between filler and physical indicators. (B) Plotting of correlation coefficients between filler and sprouting indicators.
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Figure 5. Pelleted seeds with different binders and different binder ratios exhibited differential modifications in both size parameters and appearance.
Figure 5. Pelleted seeds with different binders and different binder ratios exhibited differential modifications in both size parameters and appearance.
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Figure 6. The value of physical index ((A): seeded rate, single seed rate, disintegration rate, (B): compressive strength) of pelleted seeds under different types of binders and their concentrations. Data are represented as means ± SD of three biological replicates.
Figure 6. The value of physical index ((A): seeded rate, single seed rate, disintegration rate, (B): compressive strength) of pelleted seeds under different types of binders and their concentrations. Data are represented as means ± SD of three biological replicates.
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Figure 7. Correlation analysis of PVA (A), SA (B), CMC-Na (C) with physical indexes of pelletised seeds. Disintegration rate showed significant negative correlation with PVA and SA, and significant positive correlation with CMC-Na. The seeded rate was significantly correlated with PVA and SA, and positively correlated with CMC-Na. Single grain rate had significant negative correlation with PVA and CMC-Na and positive correlation with SA. Compression resistance has a positive correlation with PVA and SA and a significant positive correlation with CMC-Na. Where n = 3 and * represents p < 0.05.
Figure 7. Correlation analysis of PVA (A), SA (B), CMC-Na (C) with physical indexes of pelletised seeds. Disintegration rate showed significant negative correlation with PVA and SA, and significant positive correlation with CMC-Na. The seeded rate was significantly correlated with PVA and SA, and positively correlated with CMC-Na. Single grain rate had significant negative correlation with PVA and CMC-Na and positive correlation with SA. Compression resistance has a positive correlation with PVA and SA and a significant positive correlation with CMC-Na. Where n = 3 and * represents p < 0.05.
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Figure 8. The value of Germination performance ((A): Germination percentage, Germination potential, (B): Germination Index) of pelleted seeds under different types of binders and their concentrations. Data are represented as means ± SD of three biological replicates.
Figure 8. The value of Germination performance ((A): Germination percentage, Germination potential, (B): Germination Index) of pelleted seeds under different types of binders and their concentrations. Data are represented as means ± SD of three biological replicates.
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Figure 9. Correlation analysis of PVA (A), SA (B) and CMC-Na (C) with the germination indexes of pelletized seeds. The germination potential was positively correlated with PVA and SA, and negatively correlated with CMC-Na. Germination rate was positively correlated with PVA and SA, and negatively correlated with CMC-Na. Germination index was significantly positively correlated with PVA and negatively correlated with SA and CMC-Na. Where n = 3 and * represents p < 0.05.
Figure 9. Correlation analysis of PVA (A), SA (B) and CMC-Na (C) with the germination indexes of pelletized seeds. The germination potential was positively correlated with PVA and SA, and negatively correlated with CMC-Na. Germination rate was positively correlated with PVA and SA, and negatively correlated with CMC-Na. Germination index was significantly positively correlated with PVA and negatively correlated with SA and CMC-Na. Where n = 3 and * represents p < 0.05.
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Table 1. P. oleracea seed filler formula.
Table 1. P. oleracea seed filler formula.
GroupTalcum PowderKaolinBentonite
T10.00%40.0%60.0%
T2100%0.00%0.00%
T320.0%80.0%0.00%
T440.0%20.0%40.0%
T540.0%0.00%60.0%
T60.00%60.0%40.0%
T720.0%20.0%60.0%
T880.0%20.0%0.00%
T90.00%80.0%20.0%
T100.00%20.0%80.0%
T1160.0%20.0%20.0%
T1260.0%40.0%0.00%
T1320.0%0.00%80.0%
T1480.0%0.00%20.0%
T1540.0%40.0%20.0%
T1640.0%60.0%0.00%
T1720.0%40.0%40.0%
T180.00%100%0.00%
T1920.0%60.0%20.0%
T2060.0%0.00%40.0%
T210.00%0.00%100%
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Sun, J.; Liu, F.; Xu, Y.; Hu, W. Coatings Applied to the Optimization of Portulaca oleracea L. Seed Pellet Formulation Based on Mixture Design. Coatings 2025, 15, 341. https://doi.org/10.3390/coatings15030341

AMA Style

Sun J, Liu F, Xu Y, Hu W. Coatings Applied to the Optimization of Portulaca oleracea L. Seed Pellet Formulation Based on Mixture Design. Coatings. 2025; 15(3):341. https://doi.org/10.3390/coatings15030341

Chicago/Turabian Style

Sun, Jinhua, Fen Liu, Yanqin Xu, and Weiming Hu. 2025. "Coatings Applied to the Optimization of Portulaca oleracea L. Seed Pellet Formulation Based on Mixture Design" Coatings 15, no. 3: 341. https://doi.org/10.3390/coatings15030341

APA Style

Sun, J., Liu, F., Xu, Y., & Hu, W. (2025). Coatings Applied to the Optimization of Portulaca oleracea L. Seed Pellet Formulation Based on Mixture Design. Coatings, 15(3), 341. https://doi.org/10.3390/coatings15030341

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