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Article

Neodymium Exerts Biostimulant and Synergistic Effects on the Nutrition and Biofortification of Lettuce with Zinc

by
Imelda Rueda-López
,
Fernando C. Gómez-Merino
,
María G. Peralta Sánchez
and
Libia I. Trejo-Téllez
*
Colegio de Postgraduados, Campus Montecillo, Carretera México-Texcoco km 36.5, Montecillo, Texcoco C. P. 56264, Estado de México, Mexico
*
Author to whom correspondence should be addressed.
Horticulturae 2025, 11(7), 776; https://doi.org/10.3390/horticulturae11070776
Submission received: 3 June 2025 / Revised: 25 June 2025 / Accepted: 30 June 2025 / Published: 2 July 2025
(This article belongs to the Special Issue Effects of Biostimulants on Horticultural Crop Production)
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Abstract

This research aimed to evaluate the effects of different concentrations of neodymium (Nd: 0, 2.885, 5.770, and 8.655 mg L−1, referred to as Nd0, Nd1, Nd2, and Nd3, respectively) and zinc (Zn: 0.1, 0.2, and 0.3 mg L−1, designated as Zn1, Zn2, and Zn3, respectively), as well as their combined interaction, on the nutritional content of lettuce (Lactuca sativa) cv. Ruby Sky. The seedlings were grown in a floating hydroponic system under greenhouse conditions. After 48 days of treatment, leaf samples were collected to determine their nutrient content. Leaf contents of N, P, Ca, Mg, S, Fe, Mn, B, and Nd were higher with the Nd1 (2.885 mg Nd L−1 + Zn1 (0.1 mg Zn L−1) treatment. The Nd3 (8.655 mg Nd L−1) + Zn3 (0.3 mg Zn L−1) treatment significantly increased the leaf contents of Cu and Zn. The K content was higher in leaves treated with Nd2 (5.770 mg Nd L−1) + Zn3 (0.3 mg Zn L−1). The joint application of Nd and Zn had positive effects on the nutrition of hydroponic lettuce, and Nd promoted the biofortification of lettuce by increasing leaf Zn content.

Graphical Abstract

1. Introduction

Global climate change is negatively affecting agricultural production and food security in various regions of the world [1]. This is because abiotic stress factors, such as drought, salinity, waterlogging, extreme temperatures, and soil acidity, are becoming more severe and frequent as a result of climate change, decreasing agricultural yields by more than 50% [2,3]. In addition, the growing world population is putting greater pressure on food demand, which poses challenging scenarios for agricultural production systems [4].
In addition to affecting agricultural production, climate change also influences the nutritional quality of crops by reducing the content of vital biomolecules and metabolites, as well as essential elements [5]. Reducing the nutritional value of crops can lead to public health problems such as malnutrition due to micronutrient deficiency, also known as “hidden hunger”, which affects more than 2 billion people worldwide [6,7]. Among the micronutrients associated with human malnutrition, zinc (Zn) is particularly critical, given its essential role in processes such as immunological, sensory, and neurobehavioral development, reproductive health, growth, and physical development of people [8]. Deficiency of this micronutrient affects 17.3% of the world’s population [9]; it is mainly caused by a lack of dietary diversification and the consumption of foods with low levels of Zn [10]. The application of biofortification techniques represents a cost-effective strategy to enhance the micronutrient content of crops, addressing human deficiencies [11]. This technique aims to increase the concentration of a chemical element in plants through the application of inorganic fertilizers, organic fertilizers, and biofertilizers, applied to the leaves, soil, or nutrient solution [12].
Biofortification with Zn has been widely studied in cereals such as wheat (Triticum aestivum), rice (Oryza sativa), and corn (Zea mays), due to their high consumption in developing countries [13], where inadequate intake of Zn is high [14]. However, these crops have high levels of phytates, antinutrients that form insoluble complexes with Zn, reducing their absorption and accumulation [15].
In contrast, leafy vegetables such as lettuce (Lactuca sativa) represent a promising option for Zn biofortification, since they contain lower levels of phytates, favoring a greater bioavailability of this micronutrient for human consumption [16,17]. Due to its fast growth, global consumption, and suitability for hydroponic production, lettuce serves as an excellent species to evaluate biostimulation-based biofortification methods [18].
Biostimulants are emerging tools that enhance plant performance by improving growth, productivity, and stress resilience through natural or synthetic inputs [19]. Biostimulants, which can be of biological or synthetic origin, and of organic or inorganic nature [20], play an important role in agronomic biofortification because they participate in the efficient acquisition of nutrients by plants [21]. Among the inorganic biostimulants, neodymium (Nd) is classified as a beneficial element that has shown positive effects in various crops, promoting growth and nutrient absorption [22,23]. As some of its benefits have only recently been proven, Nd offers a window of opportunity to explore other beneficial effects on the biology of cultivated plants. In the current scenarios of increased demand for quality foods that have to be produced under stressful conditions exacerbated by global climate change, inorganic biostimulation through beneficial elements such as Nd is strategic to promote better crop nutrition and biofortification with essential microelements such as Zn [7]. In this research, the main effects of Nd and Zn, as well as their interaction, on the nutritional content of lettuce plants cv. Ruby Sky grown in a hydroponic system were evaluated.

2. Materials and Methods

2.1. Location and Experimental Conditions

The research was conducted in a greenhouse located in Montecillo, State of Mexico, Mexico (19.96° N, 98.9° W, at 2244 m elevation). During the experimental period, the photoperiod averaged 9 h, with daytime and nighttime temperatures of 27.9 °C and 11.6 °C, respectively. The recorded photosynthetically active radiation reached 490 μmol m−2 s−1, while relative humidity fluctuated between 31% (day) and 72% (night).

2.2. Plant Material and Growth Conditions

Lettuce seeds cv. Ruby Sky (Rijk Zwaan, Lot 1w01019728x8, Salinas, CA, USA) were sown in 200-well polystyrene trays, using peat moss (PRO-MIX FLX, Premier Tech, Rivière-Du-Loup, QC, Canada) as the substrate. Seedlings of 40 d of age were established in a floating root hydroponic system in 900 mL plastic containers, with an oxygenation system programmed every 3 h with oxygenation times of 15 min. An initial acclimatization phase of 10 days was carried out, during which seedlings received Steiner nutrient solution diluted to 50% of its standard concentration [24]. After acclimatization, the solution was replaced with a full-strength formulation.

2.3. Experimental Design and Application of Treatments

The experiment followed a completely randomized design with a factorial arrangement of two factors: neodymium (Nd) at four concentrations (0.000, 2.885, 5.770, and 8.655 mg L−1, labeled Nd0 to Nd3), and zinc (Zn) at three concentrations (0.1, 0.2, and 0.3 mg L−1, labeled Zn1 to Zn3). This resulted in a total of 12 treatment combinations.
The Nd concentrations selected for this study were based on preliminary research conducted by our group, which indicated that levels ranging from 2855 to 5770 mg Nd L−1 promote optimal plant growth and biomass accumulation [23].
In a similar way, the Zn concentrations applied in this study were determined based on previous research conducted by our group with Ruby Sky lettuce [23]. That investigation evaluated various Zn concentrations in a hydroponic system and found that levels between 0.1 and 0.3 mg L−1 effectively promoted plant growth and biomass accumulation without triggering toxicity symptoms. These concentrations fall within the lower range of those reported in other Zn biofortification studies in lettuce. For example, De Lima et al. [17] applied Zn doses up to 2.4 mg L−1 and reported favorable effects on Zn accumulation, particularly in the roots, highlighting the tissue-specific nature of Zn responses in this species.
The sources of Nd and Zn used were NdCl3 6H2O (Sigma-Aldrich, St. Louis, MO, USA) and ZnSO4 7H2O (Fermont, Monterrey, Mexico), respectively. Each treatment was replicated three times. The experimental unit consisted of a 900 mL container with one lettuce plant. The treatments were applied through the 100% Steiner universal nutrient solution, formulated with analytical grade reagents, which contained the following chemical composition of macronutrients in molc m−3: 12 NO3−, 1 H2PO4−, 7 SO42−, 7 K+, 9 Ca2+, 4 Mg2+; and micronutrients in mg L−1: 5 Fe, 0.02 Cu, 0.62 Mn, 0.44 B, and 0.10 Mo. A closed hydroponic system was implemented, where the nutrient solution with different levels of Nd and Zn was completely renewed every 10 d. The water consumed within the system was replenished every 48 h. The pH of the solution was adjusted to 5.5 using 1 N H2SO4 (Meyer, Ciudad de México, Mexico).

2.4. Variables Evaluated

Lettuce plants were harvested 48 days after treatment initiation. The leaves were oven-dried at 70 °C for 72 h (Riossa HCF-125, Guadalajara, Mexico) and then ground to pass through a 2 mm sieve.
N determination was performed using the micro-Kjeldahl method. A total of 0.25 g of each plant sample was weighed and subjected to wet digestion with a bi-acid mixture of H2SO4:HClO4 (2:1, v:v) and 1 mL of H2O2 at 30%, in a digestion plate at 350 °C. At the end of digestion, the extracts obtained were filtered and made up to 25 mL with deionized water. A volume of 10 mL of the resulting extract was distilled by adding 50% NaOH. The distillate was received in 4% H3BO3 with a mixture of indicators (methyl red and bromocresol green), and the titration was carried out with 0.05 N H2SO4.
To quantify the concentrations of P, K, Ca, Mg, S, Fe, Cu, Zn, Mn, B, and Nd, a mass of 0.5 g of dried plant tissue was used for analysis. The samples were digested with a mixture of nitric acid and perchloric acid in a 2:1 ratio (v/v) at 160 °C using a digestion plate. Following digestion, the solutions were filtered and diluted to a final volume of 25 mL with deionized water. The concentrations of the elements were then determined using inductively coupled plasma optical emission spectrometry (ICP-OES, Agilent 725-ES, Santa Bárbara, CA, USA).
With the data on the dry biomass of the leaves and the concentration of nutrients and Nd obtained, the contents of these elements were estimated.

2.5. Statistical Analysis

The data were subjected to analysis of variance (ANOVA) to evaluate the main effects and interactions of the factors. Tukey’s test (p ≤ 0.05) was used for mean comparisons with SAS statistical software, version 9.4 [25].
Additionally, a principal component analysis (PCA) was performed to explore relationships among nutrient contents and treatment effects. The PCA was conducted using R software, version 4.5.1 [26], generating biplots to visualize treatment distribution and variable contributions.

3. Results

This research evaluated the main effects of the application of neodymium (Nd) and zinc (Zn), and their interaction (Nd × Zn) on the content of macronutrients, micronutrients, and Nd in leaves of lettuce cv. Ruby Sky, with the aim of identifying their effects on nutrient and Nd absorption and accumulation.
The main factors (Nd and Zn), as well as their interactions (Nd × Zn), caused significant effects on the content of all the elements evaluated (Table 1 and Table 2). Therefore, the results of the interaction of the study factors are presented below.
The leaf contents of all macronutrients were higher in plants treated with Nd1 + Zn1, except for the K content, which was higher with the Nd3 + Zn3 treatment. Plants treated with the Zn1 level showed a decreasing trend in macronutrient content as the Nd dose in the nutrient solution was increased (Figure 1).
Specifically, the Nd1 + Zn1 treatment increased leaf N contents by 125.6 and 129.1% (Figure 1A), P by 122.5 and 122.8% (Figure 1B), Ca by 103 and 92.9% (Figure 1D), Mg by 98.9 and 91.4% (Figure 1E), and S by 107.5 and 113% (Figure 1F), compared to the Zn2 and Zn3 supply without Nd, respectively. The treatment Nd2 + Zn3 increased the leaf concentration of K by 225.6%, compared to the application of Nd3 + Zn2 (Figure 1C).
Leaf Fe content was reduced by 44.6% in plants treated with Zn2 without Nd (Nd0), compared to the Nd1 + Zn1 treatment (Figure 2A). For its part, the Nd3 + Zn3 treatment increased leaf Cu contents by 192 and 194.7% and Zn contents by 151.5 and 173.6%, compared to the application of Zn2 and Zn3 without Nd, respectively (Figure 2B,C).
The Nd1 + Zn1 treatment increased leaf Mn and B contents on average by 38.3 and 30.5%, respectively, compared to all other treatments (Figure 2D,E). The highest leaf Nd content was recorded in plants treated with Nd1 + Zn1, with respect to all treatments (Figure 2F).
The principal component analysis (PCA), based on the concentrations of macro- and micronutrients as well as Nd, revealed that the first two principal components explained 76.3% and 8.0% of the total variance, respectively, accounting for a combined 84.3% of the overall variability. The PCA biplot of treatments (Figure 3) showed a clear separation along PC1, where treatments receiving higher concentrations of Nd and Zn clustered on the positive side of the axis. In contrast, control treatments and those with lower Zn levels were located on the negative side of PC1.
The relationships among the measured variables and their contributions to the first two principal components are illustrated in the PCA biplot of variables (Figure 4). Most nutrient concentrations, including N, P, K, Ca, Mg, S, Fe, Mn, B, and Nd, showed a positive association with PC1. Zinc and Cu contributed more prominently along PC2, with Cu exhibiting a strong association in the positive direction of this axis.
These multivariate patterns aligned with the results of the factorial analysis, which demonstrated that both Nd and Zn applications significantly influenced Zn concentration in lettuce leaves, with a highly significant interaction between these factors (Table 2). At Zn1, Zn content increased progressively with higher Nd doses, reaching a maximum value of 140.08 mg kg−1 dry matter at Nd3. At Zn2, the highest Zn concentration (129.95 mg kg−1 dry matter) was observed with Nd2. At Zn3, the greatest Zn accumulation (179.78 mg kg−1 dry matter) occurred with the combined application of Nd3 and Zn3 (Figure 2C).

4. Discussion

Neodymium (Nd) belongs to the group of rare earth elements (REEs), which also includes lanthanum (La), cerium (Ce), praseodymium (Pr), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), scandium (Sc), and yttrium (Y) [27,28]. Although not classified as essential, REEs have demonstrated beneficial roles in enhancing growth and nutrient dynamics in key crops [28,29,30]. REEs can interact synergistically or antagonistically with other essential elements, modulating nutrient absorption, accumulation, and utilization [31,32,33]. For example, in the aquatic plant, yellow floating heart (Nymphoides peltata), the application of 1–5 mg Y L−1 increased leaf concentrations of Mg, Ca, Fe, Mn, and Mo, and reduced those of P and K [34]. In rice, leaf application of REE (Ce, La, Pr, and Nd) significantly increased leaf concentrations of N, K, Mg, and Mn with the treatment 0.5 kg REE ha−1 [33]. In contrast, in rice leaves, the application of 100 and 1000 µM Nd decreased the concentrations of K, Ca, Mg, Fe, Cu, Zn, and Mn [35].
Under our experimental conditions, the joint supply of different concentrations of Nd and Zn in the nutrient solution caused differential effects on the leaf content of the evaluated nutrients. The Nd1 + Zn1 treatment significantly increased leaf N, P, Ca, Mg, S, Fe, Mn, and B contents compared with the Zn1 treatment without Nd (Figure 1A,B,D–F and Figure 2A,D,E). Compared with the Zn1 treatment without Nd, the leaf P and Cu contents increased with the Nd2 + Zn3 and Nd3 + Zn3 treatments, respectively (Figure 1C and Figure 2B). The results obtained here are consistent with those reported for N, P, and K in sugarcane (Saccharum spp.) plants treated with 21.6 mg Nd L−1 [22]. These findings suggest that Nd acts synergistically with nutrients, enhancing their absorption, accumulation, and translocation.
The positive effect of Nd on nutritional status is possible because REEs have chemical activities and ionic radii (0.93 to 1.16 nm) similar to Ca, Mg, and K (0.99, 0.65, and 1.33 nm, respectively); as a result, they have effects on the absorption and accumulation of certain nutrients [36,37,38,39].
Biofortified lettuce can provide more nutrients compared to other cooked or processed vegetables and cereals; therefore, its fresh consumption can benefit human health [40]. In mung bean (Vigna radiata) plants, leaf Zn content increased by 0.065 and 0.13 mg Zn L−1 in treatments [41]. In lettuce cv. Phillipus, Zn content increased from 132.07 to 209.33 µg in leaves treated with 0.7 to 2.4 mg Zn L−1, respectively [42]. In our study, the highest leaf Zn content (179.78 µg) was recorded with the Nd3 + Zn3 treatment (Figure 1C). Based on the results of the Zn content obtained and considering the average recommended dietary intake of this nutrient in adults (11 mg Zn day−1) [43], it was estimated that the Ruby Sky cv. contributes 1.6% to the daily Zn intake required by humans. These contributions coincide with those reported by de Almeida et al. [11] in the Regina de Verano and Delicia lettuce genotypes, and are higher than those provided by the potato (Solanum tuberosum) genotype Saxon [44], broccoli sprouts (Brassica oleracea var. italica), pea (Pisum sativum), sunflower (Helianthus annuus) [45], and Genovese basil (Ocimum basilicum) cv. Aroma 2 [46]. Although lettuce contributions represent a small contribution to daily Zn intake, its biofortification helps to cover Zn needs in people, since it is the most produced and consumed leafy vegetable in the world.
It was observed that the application of Nd caused a positive effect on Zn biofortification. All plants treated with Nd exhibited higher Zn contents compared to those grown without Nd, regardless of the level of Zn supplied (Figure 2D). Nutrient absorption by the roots, followed by their loading in the xylem, are the main steps in the acquisition and accumulation of nutrients in plants [47]. These functions are performed by specific transporter proteins that regulate inter- and intracellular transport [48], which include members of the ZIP [Zn and Fe permease family, similar to ZRT (Zn transporters) and IRT (Fe-regulated transporters)], MTP (metal tolerance proteins), and heavy metal ATPases (HMAs) families [49]. Zn2+ transport is dependent on a change in membrane potential, maintained by H+-ATPase activity, which promotes H+ efflux and controls its flux by promoting its transport [50]. In this study, Nd supply increased leaf Zn concentration, which may be due to its effect on H+-ATPase activity. Previous studies have documented that an adequate concentration of La3+ increases the activity of H+-ATPase in rice [47] and casuarina (Casuarina equisetifolia) [51], stimulating the uptake of P, Ca, Mg, Mn, and Zn [52,53].
In several cultivable species, a higher concentration of REE has been reported as the concentration of these in the growth medium increases [54]. In rice and wheat, the concentrations of Nd in shoot and root were directly related to the doses supplied [55]. However, in this study, the leaf content of Nd was higher with the treatment Nd1 + Zn1 (Figure 2E). These results could be due to the fact that lettuce plants activated mechanisms that inhibit the transport of Nd to the aboveground part, with the consequent accumulation of Nd and other metals [56]. In rice seedlings, Nd was mainly deposited in the cell wall of the roots, forming insoluble precipitates with oxalate, phosphate, and pectate. Chelation of Nd by these salts restricted its transport to the shoot [57]. In the fern Dicropteris dichotoma, REE La, Ce, Pr, and Nd were mostly deposited in the cell wall, intercellular space, plasmalemma, and vacuoles of the root endodermis [58]. Similarly, high concentrations of Ce and Y were localized in the vacuoles and cell walls in the roots of rice plants [59,60]. In hydroponically grown soybean (Glycine max), low translocation of La from the root to the shoot was recorded, and its transport decreased as the concentration of La increased in the nutrient solution [61].
The application of REE combined with fertilizers in agriculture has generated controversy due to their entry into the food chain through the consumption of plant species, which could have negative effects on human health [62,63]. Currently, there are no official values of the acceptable daily intake (ADI) of total or individual REEs [64,65]. In vegetables and cereals, the average concentrations of REEs and their associated risks to human health were evaluated, concluding that 70 μg kg−1 d−1 is the maximum dose of these elements for the consumption of both types of crops [66,67]. The temporary acceptable daily intake (tADI) for lanthanum (La), cerium (Ce), and yttrium (Y) was established by the National Center for Food Safety Risk Evaluation of China at 51.5, 645, and 145.5 μg kg−1 of body weight, respectively. These values were determined based on no-observed-adverse-effect levels (NOAELs) obtained from toxicological evaluations. Also, the dietary exposure to REE was evaluated, and the tADI of La was established for the rest of REE [64,68,69]. The reference ADI is 51.5 μg kg−1 BW [35,70,71], a value that was used to evaluate the possible health risk associated with the ingestion of Nd-biostimulated lettuce. Considering an ADI of 3.6 mg d−1 REE (for an adult with an average weight of 70 kg), the maximum leaf Nd content recorded in this research (53.5 µg Nd) (Figure 2E) is low; thus, a daily consumption of 91 lettuces is needed to exceed the permitted limit. Importantly, Nd appears to hold great promise for both diagnostic and therapeutic purposes [72], while health risks have been reported only when supplied as Nd(NO3)3 at approximately 17 to 32 mg kg−1 [73].
The uptake and transport mechanisms of REEs in plants are still poorly understood. In marigold (Tagetes erecta) roots, a positive relationship was found between REEs and Mn, Al, Fe, and Cu, which raised the hypothesis that these elements share transporters [74]. The natural resistance-associated macrophage protein (NRAMP) family plays a key role in regulating manganese (Mn) homeostasis in plants, with notable examples including AtNramp1 to AtNramp4 in Arabidopsis thaliana and OsNramp3 in rice [75]. Moreover, certain NRAMP transporters have been associated with the uptake and detoxification of aluminum (Al3+), such as OsNrat1 in rice and SbNrat1 in sorghum (Sorghum bicolor). In the hyperaccumulator fern Dicranopteris linearis, the NRAMP1 transporter known as NREET1 was identified, demonstrating a high affinity for light rare earth elements (LREEs) like neodymium (Nd), lanthanum (La), cerium (Ce), and praseodymium (Pr), while showing no transport activity for divalent metals such as Zn2+, Ni2+, Mn2+, or Fe2+ [75]. It has been proposed that Al3+ transporters represent the main pathway for REE uptake and transport in plants, followed by mechanisms linked to calcium (Ca) and manganese (Mn) transport [76,77].
The enhancement of zinc content in lettuce leaves following the combined application of neodymium and zinc suggests that Nd may play a role in influencing Zn acquisition and distribution mechanisms within the plants. This synergistic effect aligns with previous research, highlighting the involvement of REEs in modulating nutrient uptake pathways. Furthermore, the increase in Zn levels with higher Nd doses, particularly when combined with Zn concentrations between 0.1 and 0.3 mg L−1, underscores the potential contribution of rare earth elements to improving Zn biofortification in lettuce. This trend was further supported by the principal component analysis (PCA), which demonstrated a clear association between treatments with elevated Nd and Zn concentrations and enhanced nutrient accumulation in leaf tissue.
The present results on nutrient accumulation in lettuce leaves align with the growth responses previously documented by our research group under the same experimental conditions [23]. In that earlier study, applications of Nd and Zn significantly enhanced plant height, leaf area, and biomass accumulation, reflecting improved nutritional status and overall physiological performance. The current findings further confirm the beneficial role of Nd and Zn in promoting plant nutrition and underscore the potential of these elements to enhance lettuce production and quality.
Considering the beneficial effects that certain REEs, including Nd, have shown in plant biology, it is crucial to continue investigating their role in nutrient accumulation and plant development. Although the present study did not directly assess the physiological or molecular mechanisms involved, the observed synergistic effect of Nd and Zn on lettuce nutrient status may be associated with known actions of REEs, such as enhancing nutrient uptake by altering membrane permeability, activating proton pumps like H+-ATPases, or interacting with nutrient transporters from the ZIP, NRAMP, and HMA families. Expanding research to other cultivated species and incorporating advanced physiological, biochemical, and molecular approaches will be essential to clarify these mechanisms. Gaining deeper insight into these processes will contribute to developing more effective management strategies to improve Zn biofortification, promote agricultural sustainability, and enhance food security.

5. Conclusions

The results of this study demonstrate that the combined application of neodymium and zinc at different concentrations produces distinct effects on the nutrient composition of lettuce leaves. The use of Nd as an inorganic biostimulant not only improved the nutritional status of the plants but also contributed to enhancing zinc biofortification in lettuce grown under hydroponic conditions.
These findings provide useful evidence of the potential of neodymium as a tool to improve both the nutritional quality and the agronomic value of lettuce. Incorporating Nd into biofortification strategies may represent a promising approach to address micronutrient deficiencies in human diets, particularly in leafy vegetables such as lettuce, which are widely consumed worldwide.
Future research should continue exploring the physiological and molecular mechanisms behind these effects and assess the long-term safety and efficacy of using rare earth elements in agricultural production.

Author Contributions

Conceptualization, L.I.T.-T.; methodology, I.R.-L. and M.G.P.S.; software, L.I.T.-T. and F.C.G.-M.; validation, F.C.G.-M. and L.I.T.-T.; formal analysis, L.I.T.-T.; investigation, I.R.-L.; resources, L.I.T.-T. and F.C.G.-M.; data curation, L.I.T.-T.; writing—original draft preparation, I.R.-L. and L.I.T.-T.; writing—review and editing, F.C.G.-M. and M.G.P.S.; visualization, I.R.-L.; supervision, L.I.T.-T. and F.C.G.-M.; project administration, L.I.T.-T.; funding acquisition, L.I.T.-T. and F.C.G.-M. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Data Availability Statement

Data will be made available on request.

Acknowledgments

The Secretary of Science, Humanities, Technology and Innovation (SECIHTI, before CONAHCYT) of Mexico granted a Master of Science scholarship to I.R.-L.

Conflicts of Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

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Horticulturae 11 00776 g001
Figure 1. Effect of applying different concentrations of Nd (0.000, 2.885, 5.770, and 8.655 mg L−1) and Zn (0.1, 0.2, and 0.3 mg L−1) on leaf nitrogen (A), phosphorus (B), potassium (C), calcium (D), magnesium (E), and sulfur (F) content in lettuce cv. Ruby Sky. Means ± SD with different letters in each subfigure are statistically different (Tukey, p ≤ 0.05).
Figure 1. Effect of applying different concentrations of Nd (0.000, 2.885, 5.770, and 8.655 mg L−1) and Zn (0.1, 0.2, and 0.3 mg L−1) on leaf nitrogen (A), phosphorus (B), potassium (C), calcium (D), magnesium (E), and sulfur (F) content in lettuce cv. Ruby Sky. Means ± SD with different letters in each subfigure are statistically different (Tukey, p ≤ 0.05).
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Figure 2. Effect of different concentrations of Nd (0.000, 2.885, 5.770, and 8.655 mg L−1) and Zn (0.1, 0.2, and 0.3 mg L−1) on the leaf content of iron (A), copper (B), zinc (C), manganese (D), boron (E) and neodymium (F) in lettuce cv. Ruby Sky. Means ± SD with different letters in each subfigure are statistically different (Tukey, p ≤ 0.05).
Figure 2. Effect of different concentrations of Nd (0.000, 2.885, 5.770, and 8.655 mg L−1) and Zn (0.1, 0.2, and 0.3 mg L−1) on the leaf content of iron (A), copper (B), zinc (C), manganese (D), boron (E) and neodymium (F) in lettuce cv. Ruby Sky. Means ± SD with different letters in each subfigure are statistically different (Tukey, p ≤ 0.05).
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Horticulturae 11 00776 g003
Figure 3. Principal component analysis (PCA) biplot illustrating the distribution and grouping of treatments according to the first two principal components (Dim1 and Dim2), which account for 76.3% and 8.0% of the total variance, respectively. Treatments correspond to different combinations of Nd and Zn concentrations (Nd0 = 0 mg Nd L−1; Nd1 = 2.885 mg Nd L−1; Nd2 = 5.770 mg Nd L−1; Nd3 = 8.655 mg Nd L−1; Zn1 = 0.1 mg Zn L−1; Zn2 = 0.2 mg Zn L−1; Zn3 = 0.3 mg Zn L−1). The ellipses represent the 95% confidence intervals for each treatment group.
Figure 3. Principal component analysis (PCA) biplot illustrating the distribution and grouping of treatments according to the first two principal components (Dim1 and Dim2), which account for 76.3% and 8.0% of the total variance, respectively. Treatments correspond to different combinations of Nd and Zn concentrations (Nd0 = 0 mg Nd L−1; Nd1 = 2.885 mg Nd L−1; Nd2 = 5.770 mg Nd L−1; Nd3 = 8.655 mg Nd L−1; Zn1 = 0.1 mg Zn L−1; Zn2 = 0.2 mg Zn L−1; Zn3 = 0.3 mg Zn L−1). The ellipses represent the 95% confidence intervals for each treatment group.
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Horticulturae 11 00776 g004
Figure 4. Principal component analysis (PCA) biplot illustrating the contribution and orientation of the measured variables to the first two principal components. The length and direction of the arrows represent the strength and association of each variable with PC1 and PC2. Treatments correspond to different combinations of Nd and Zn concentrations (Nd0 = 0 mg Nd L−1; Nd1 = 2.885 mg Nd L−1; Nd2 = 5.770 mg Nd L−1; Nd3 = 8.655 mg Nd L−1; Zn1 = 0.1 mg Zn L−1; Zn2 = 0.2 mg Zn L−1; Zn3 = 0.3 mg Zn L−1).
Figure 4. Principal component analysis (PCA) biplot illustrating the contribution and orientation of the measured variables to the first two principal components. The length and direction of the arrows represent the strength and association of each variable with PC1 and PC2. Treatments correspond to different combinations of Nd and Zn concentrations (Nd0 = 0 mg Nd L−1; Nd1 = 2.885 mg Nd L−1; Nd2 = 5.770 mg Nd L−1; Nd3 = 8.655 mg Nd L−1; Zn1 = 0.1 mg Zn L−1; Zn2 = 0.2 mg Zn L−1; Zn3 = 0.3 mg Zn L−1).
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Table 1. Significance of the study factors and their interaction in the leaf macronutrient contents in lettuce (Lactuca sativa) cv. ‘Ruby Sky’ plants.
Table 1. Significance of the study factors and their interaction in the leaf macronutrient contents in lettuce (Lactuca sativa) cv. ‘Ruby Sky’ plants.
Study FactorsNPKCaMgS
Nd<0.0001 *<0.0001 *<0.0001 *<0.0001 *<0.0001 *<0.0001 *
Zn<0.0001 *<0.0001 *<0.0001 *<0.0001 *<0.0001 *<0.0001 *
Nd × Zn<0.0001 *<0.0001 *<0.0001 *<0.0001 *<0.0001 *<0.0001 *
* = significant (p ≤ 0.05).
Table 2. Significance of the study factors and their interaction in the leaf micronutrient contents in lettuce (Lactuca sativa) cv. ‘Ruby Sky’ plants.
Table 2. Significance of the study factors and their interaction in the leaf micronutrient contents in lettuce (Lactuca sativa) cv. ‘Ruby Sky’ plants.
Study FactorsFeCuZnMnBNd
Nd<0.0001 *<0.0001 *<0.0001 *<0.0001 *<0.0001 *<0.0001 *
Zn<0.0001 *<0.0001 *<0.0001 *<0.0001 *<0.0001 *0.0217 *
Nd × Zn<0.0001 *<0.0001 *<0.0001 *<0.0001 *<0.0001 *<0.0001 *
* = significant (p ≤ 0.05).
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Rueda-López, I.; Gómez-Merino, F.C.; Peralta Sánchez, M.G.; Trejo-Téllez, L.I. Neodymium Exerts Biostimulant and Synergistic Effects on the Nutrition and Biofortification of Lettuce with Zinc. Horticulturae 2025, 11, 776. https://doi.org/10.3390/horticulturae11070776

AMA Style

Rueda-López I, Gómez-Merino FC, Peralta Sánchez MG, Trejo-Téllez LI. Neodymium Exerts Biostimulant and Synergistic Effects on the Nutrition and Biofortification of Lettuce with Zinc. Horticulturae. 2025; 11(7):776. https://doi.org/10.3390/horticulturae11070776

Chicago/Turabian Style

Rueda-López, Imelda, Fernando C. Gómez-Merino, María G. Peralta Sánchez, and Libia I. Trejo-Téllez. 2025. "Neodymium Exerts Biostimulant and Synergistic Effects on the Nutrition and Biofortification of Lettuce with Zinc" Horticulturae 11, no. 7: 776. https://doi.org/10.3390/horticulturae11070776

APA Style

Rueda-López, I., Gómez-Merino, F. C., Peralta Sánchez, M. G., & Trejo-Téllez, L. I. (2025). Neodymium Exerts Biostimulant and Synergistic Effects on the Nutrition and Biofortification of Lettuce with Zinc. Horticulturae, 11(7), 776. https://doi.org/10.3390/horticulturae11070776

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