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Article

The Influence of Foliar Application of Nod Factors (LCOs) and Microelements on the Growth, Development, and Yield of Peas (Pisum sativum L.)

by
Janusz Podleśny
1,
Jerzy Wielbo
2,*,
Anna Podleśna
1,
Hanna Klikocka
3 and
Dominika Kidaj
2
1
Institute of Soil Science and Plant Cultivation—State Research Institute, Czartoryskich 8, 24-100 Puławy, Poland
2
Department of Genetics and Microbiology, Maria Curie-Sklodowska University, Akademicka 19, 20-033 Lublin, Poland
3
Department of Economics and Agribusiness, Faculty of Agrobioengineering, University of Life Sciences in Lublin, Akademicka 13, 20-950 Lublin, Poland
*
Author to whom correspondence should be addressed.
Agronomy 2025, 15(11), 2536; https://doi.org/10.3390/agronomy15112536
Submission received: 19 September 2025 / Revised: 25 October 2025 / Accepted: 29 October 2025 / Published: 31 October 2025
(This article belongs to the Special Issue Crop Productivity and Management in Agricultural Systems)
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Abstract

Peas are a popular crop grown in Poland, but their yields are variable and often low; therefore, new cultivation methods are constantly being sought. In this paper, we present the results of a three-year greenhouse study examining the effect of preparations containing rhizobial Nod factors and/or selected microelements (B, Cu, Fe, Mn, Zn, and Mo) on the physiological parameters, growth, and yield of peas. Pea plants were tested at the flowering stage (BBCH 60), at the green ripe stage (BBCH 75), and at the fully ripe stage (BBCH 90). Leaf area, SPAD, gas exchange parameters, and chlorophyll fluorescence were measured, and the number and mass of root nodules, as well as seed yield and yield components, were determined. The treatment was most effective when Nod factors were used in combination with microelements. The increase in pea yield induced by the application of both components can be attributed to the higher number of pods and seeds per plant because no significant variations were noted in the number of seeds per pod and 1000 seed weight. The number and weight of nodules were significantly correlated with the pea yield, and the value of the correlation coefficients was influenced by the application of both components.

1. Introduction

Peas are one of the major legume crops in the Polish climate zone [1]. Despite numerous advantages of pea plants, including their beneficial influence on the soil environment, high protein content in seeds, and high suitability for animal and human nutrition, they are characterized by relatively low and highly varied seed yields across years [2]. This weakness is largely responsible for the relatively small acreage of peas. Therefore, the efforts aiming to develop new cultivars should be accompanied by a search for new methods to increase the yield of peas, for example, by increasing the levels of plant-available nitrogen through improvement in the effectiveness of symbiotic nitrogen fixation [3]. Data available in the literature suggest that symbiotically reduced N2 may supply more than half of the total requirement of the plant [3,4,5,6]. Therefore, research on the use of symbiotic microorganisms for legume crops, or bacterial metabolites, which increase the efficiency of symbiosis, is a promising strategy leading to increased yields.
Research into symbiotic relationships between legumes and rhizobia allowed the identification of numerous plant and bacterial metabolites that promote symbiosis and the development of root nodules. The most important are bacterial Nod factors (lipochitooligosaccharides, LCOs), i.e., signal molecules that induce the formation of root nodules in legumes [7]. These signal molecules are responsible for the activation of signal transmission pathways and the expression of plant genes, as well as having an influence on the level and distribution of phytohormones. This results in morphogenetic changes such as cortical cell division, and these new meristematic cells that appear in the primary root cortex will give rise to meristems responsible for the growth and development of root nodules [8,9,10]. In numerous greenhouse or field experiments, Nod factors used for seed dressing improved pea nodulation, thus increasing plant nitrogen content as well as pea growth and yield [11,12]. Moreover, it was demonstrated that rhizobial LCOs used together with other compounds like lumichrome [13] or sulfur [14] may bring even better results than using Nod factors alone.
The development of symbiotic interactions between the plant host and endosymbiotic rhizobia is largely dependent on the availability of micronutrients. For example, molybdenum and iron are cofactors of nitrogenase and nitrogenase reductase—the most important enzymes responsible for the biological reduction of dinitrogen to ammonia [15,16,17,18]. Furthermore, iron is essential for the synthesis of leghemoglobin, which provides a microaerophilic environment in host plant cells, and for the synthesis of cytochromes within nitrogen-reducing bacteroids [19]. Copper, zinc, and manganese are cofactors of numerous antioxidant enzymes active in plant and bacterial cells, protecting root nodules from free radicals [20,21]. This is not the only role of these ions in symbiosis, as, for example, manganese is essential for the adhesion of rhizobia to the surface of root hairs [22], and copper is a component of cbb3-type oxidase, which functions in the process of microaerobic respiration of endosymbiotic rhizobial bacteroids [23]. Boron, in turn, is essential for the endocytosis of bacteria by plant cells and is responsible for the proper functioning of cell membranes, which serve as a surface for the exchange of ions and metabolites between microsymbionts and their plant host [24].
Micronutrients also influence many other developmental and physiological processes of plants, and their deficiency can significantly limit the efficiency of the most important of them, such as photosynthesis. This may happen as a result of changes in individual processes or the structures in which they take place. For example, Fe [25], B [26], or Mo [27] deficiency can significantly reduce net photosynthesis efficiency. The lack of Mn results in the disorganization of photosynthetic electron transport [28], whereas Zn deficiency can be responsible for the inhibition of photosystem II light-harvesting activity [29]. In turn, the amount of chlorophyll produced is reduced due to deficiency of B [26], Cu [30], or Zn [31]. Finally, major changes in the structure of chloroplasts may occur due to a deficiency of Cu [30], Mn [28], or Zn [31]. It should also be noted that the presence of individual microelements is necessary for the proper functioning of biochemical systems operating at the level of the entire multicellular organism—for example, an appropriate level of Mo, affecting N metabolism, is responsible for maintaining a high level of nitrogen and protein in plant tissues [27,32]. Therefore, considering the existence of numerous mechanisms responsible for the transport of ions from plant cells to symbiotic rhizobia living within them [33,34], it can be assumed that treating plants with micronutrients may have a beneficial effect not only on their growth and development but also on the intensification of symbiotic interactions with their bacterial microsymbionts living within root nodules.
In this paper, we present the results of research testing the effect of a preparation containing Nod factors and selected microelements (B, Cu, Fe, Mn, Mo, and Zn), which was intended to enhance the effectiveness of symbiotic interactions in the pea–rhizobia system and thus to increase pea growth and yield.
This action, composed of two elements (Nod factors and microelements), is particularly important because even in soils with average microelement levels, plants may be deficient in microelements during periods of drought or in soils with suboptimal pH. This situation is similar to that observed for Nod factors: LCOs are synthesized by rhizobia living in the rhizosphere, but may be diffused or degraded by soil-dwelling microorganisms [35]. Therefore, administering an additional dose of LCOs in the form of a biopreparation could increase the effectiveness of symbiosis as a result of the emergence of an additional pool of root nodules [11,12,13,14], and the beneficial effect of a set of microelements may be an additional factor increasing plant yields.

2. Materials and Methods

2.1. Growth Conditions

The three-year experiment was carried out in the greenhouse of the Institute of Soil Science and Plant Cultivation—State Research Institute in Puławy, Poland. Ten pea seeds cv. Medal (afila genotype) were sown per the Mitscherlich pot (single pot was an independent replicate), filled with a mixture of 5 kg of soil and 2 of sand. The basic chemical properties of soil were as follows: pHKCl—6.8, NTotal—0.29%, and Corg 0.82%. The amount of macro- and micronutrients was as follows (in mg/kg of soil): mineral N-NO3—7.6, mineral N-NH4—5.6, P—514, K—564, Mg—16.1, B—0.50, Cu—2.17, Fe—465, Mn—60.7, Zn—2.37, and Mo—0.01. Seedlings were thinned after emergence, and five plants were left per pot. The plants were supplied with mineral fertilizers (g pot−1): N—0.1, P—1.1, and K—1.4. The fertilizers were applied in a liquid form when watering the seedlings. Soil moisture was kept constant at 60% field water capacity throughout the growing season. The plants were watered twice daily with demineralized water. The amount of water supplied to pots was determined with the gravimetric method. Throughout the entire experiment, the plants used only natural light.

2.2. Experimental Factors

The first-order factor was the sprayed preparation: 1—control (distilled water), 2—Nod factors (LCOs) at a concentration of 10−11 M/dm−3 water, and 3—the microelements (MEs) (mg pot−1) B—1.2, Cu—0.8, Fe—1.0, Mn—1.5, Mo—0.5, and Zn—2.0, which were applied in the form of chelates. Each experimental group contained four Mitscherlich pots with plants treated with water, LCOs, MEs, or LCOs + MEs, respectively. The pea plants were sprayed with 25 mL of the preparation per pot in the 4-leaves-unfolded stage—BBCH 14 [36]. The second-order factor was the harvest date: 1—in the flowering stage (BBCH 60), 2—in the green ripe stage (BBCH 75), and 3—in the fully ripe stage (BBCH 90).

2.3. Preparation of the LCO Extract

Rhizobial Nod factors were isolated from a liquid culture of the Rhizobium leguminosarum bv. viciae GR09 (Rlv GR09) strain. The extract containing rhizobial Nod factors was prepared, chemically analyzed, and subjected to an evaluation of biological activity in accordance with the previously described methods [37]. Based on the assumption that a single Nod factor molecule contains, on average, four GlcNAc residues, the concentration of Nod factors was estimated at 260 nM, and the concentration of Nod factors in the sprayed extract was approximately 10−11 M.

2.4. Measurements of Leaf Area and SPAD

Plant height and the number of leaves per plant were determined in the flowering stage. Leaf area (AM300 Portable Leaf Area Meter; ADC BioScientific Ltd., Hertfordshire, UK) and the SPAD greenness indicator (Chlorophyll Meter SPAD-502 Plus; Minolta Co., Ltd., Osaka, Japan) were determined. The values of the SPAD indicator were expressed as means from 30 measurements performed on true leaves from the same treatment.

2.5. Determination of Gas Exchange Parameters

Gas exchange parameters, including the net photosynthetic rate (Pn), the rate of transpiration (E), and stomatal conductance (Gs), were determined in the flowering stage with the use of a photosynthesis system equipped with a PLC(U) cuvette with a 25 mm × 7 mm window and a LED light source (Portable Photosynthesis System CIRAS-2; PP System USA). The leaves were subjected to photosynthetically active radiation (PAR) of 500 µmol m−2 s−1 and CO2 at 380 ppm. The water-use efficiency was calculated from the following formula: WUE = Pn/E (µmol CO2 mmol−1 H2O). The measurements were performed on the youngest, fully developed leaf, counting from the tip of the plant. The results were expressed as means from three measurements.

2.6. Chlorophyll Fluorescence Measurements

Chlorophyll fluorescence was determined at the flowering stage using the Handy-PEA fluorometer (Hansatech Instruments, King’s Lynn, UK). The measurements were performed on the youngest, fully developed leaf, counting from the tip of the plant. The results were expressed as means from three measurements. The following parameters were determined: F0, Fm, Fv/Fm, Area, Pindex (PI), and Tfm.

2.7. Determination of Nitrogen Content in Parts of Plants

Samples from the above-ground parts of plants were collected during flowering, and seed samples were collected after harvest. Nitrogen content was determined using the continuous flow analysis (CFA) method followed by spectrometric detection.

2.8. Determination of the Relative Growth Rate (RGR)

The rate of weight increase was determined in plants harvested in three growth stages: 1—in the flowering stage (BBCH 60), 2—in the green ripe stage (BBCH 75), and 3—in the fully ripe stage (BBCH 89). The fresh weight and dry weight of plant organs were determined in every harvested batch.
The rate of weight increase was determined based on the relative growth rate (RGR) with the use of the formula proposed by Evans [38]:
RGR = (lnW2 − lnW1) (T2 − T1)−1 [g (g·day−1)−1]
where
W1—Dry weight at the beginning of measurement;
W2—Dry weight at the end of measurement;
T1—Beginning of measurement;
T2—End of measurement.
Roots were rinsed on steel mesh sieves, nodules were removed, and the number, fresh weight, and dry weight of root nodules were determined.

2.9. Determination of Seed Yield and Yield Components

The seed weight per plant, the number of pods per plant, the number of seeds per pod, and the number of seeds per plant were determined in pea plants harvested in the fully ripe stage. Thousand-seed weight was calculated as an indicator of seed size and seed plumpness. The seed yield was recalculated for 14% moisture content and expressed per pot as an experimental unit.

2.10. Statistical Analysis

The results were expressed as mean values per four pots. Data were processed by analysis of variance (ANOVA) and regression analysis in the Statgraphics Plus 5 application at a significance level of p ≤ 0.05.

3. Results

3.1. The Effect of LCOs and/or ME Application on Morphological Traits of Pea

Pea seedlings emerged seven days after sowing. The rate of emergence was high, and the emergence uniformity was estimated at 96%, which can be largely attributed to the very high quality of the pea seeds (98% germination capacity).
The treatments with both the Nod factors and the microelements stimulated pea growth, resulting in increased morphological parameters. However, the number of leaves was significantly increased only after the LCO + ME application, while the increase in the plant height and leaf area was similar in all the experimental groups (Table 1).

3.2. The Effect of LCOs and/or MEs Application on Physiological Parameters of the Pea

Pea plants sprayed with LCOs or microelements were characterized by improved gas exchange parameters, and the best results were noted when both preparations were used in combination (Table 2). The net photosynthetic rate was significantly increased after LCOs, MEs, and LCOs + MEs treatment by 13.9%, 11.3%, and 18.2%, respectively. Application of LCOs, MEs, and LCOs + MEs together resulted in a significant increase in transpiration rate by 33.4%, 17.5%, and 31.7%, respectively. Stomatal conductance was also increased after LCOs, MEs, and LCOs + MEs treatment by 16.4%, 15.4%, and 4.4%, but this increase was insignificant when LCOs and MEs were applied together. The application of LCOs and microelements significantly increased SPAD values, and the best results were achieved in the LCOs and LCOs + MEs treatments. Simultaneously, an insignificant decrease in WUE values was observed in all the experimental groups (Table 2).
The application of LCOs and/or microelements affected chlorophyll fluorescence parameters (Table 3): the F0, and Tfm values were significantly reduced, whereas the Pindex and Fv/Fm ratio values were significantly elevated in all the experimental groups.

3.3. The Effect of LCOs and/or MEs Application on the Nodulation of the Pea

The mean number and weight of nodules and the weight of individual root nodules were determined at 96.7 nodules, 88.5 mg, and 0.91 mg, respectively, in the flowering stage, and at 69.2 nodules, 90.6 mg, and 1.31 mg, respectively, in the green ripe stage (Table 4).
The foliar application of LCOs and microelements significantly influenced the analyzed nodule parameters in the flowering stage (BBCH 60). The application of LCOs only, microelements only, and both preparations increased the number of root nodules by 8.9%, 9.2%, and 19.5%, respectively, and increased the nodule weight by 11.1%, 8.3%, and 16.4%, respectively. No significant differences were observed in the weight of individual nodules.
The number and weight of root nodules were not significantly affected by the foliar application of the Nod factors or the microelements in the green ripe stage (BBCH 75). Differences in the weight of individual nodules were noted only between plants sprayed with both preparations and the control. It should be noted that the number of root nodules decreased by 21.0% in the green ripe stage relative to the flowering stage, whereas no significant changes were observed in the weight of root nodules per plant. As a result, the weight of individual nodules increased by 15.3% in the green ripe stage.
Both the use of LCOs and ME resulted in a significant increase in nitrogen content in the above-ground parts of plants at BBCH-60 and a significant increase in nitrogen content in seeds at BBCH-89. The best effect was achieved after the use of LCOs (alone or together with ME). In both cases, an increase in nitrogen content in the above-ground parts of plants by 17.7% and an increase in nitrogen content in seeds by 12.3% were observed (Table 4).

3.4. The Effect of LCOs and/or MEs Application on Pea Growth and Yield

The greatest increase in the dry weight of above-ground plant parts and roots was noted between the flowering stage and the green ripe stage (Table 5). The ratio between the weight of vegetative organs and the weight of generative organs varied between the successive stages of growth. In developing plants, the weight of generative organs continued to increase relative to the weight of vegetative organs.
The foliar application of LCOs or microelements enhanced the growth rate of above-ground plant parts and roots, and the highest increase was observed when both preparations were used. The combined use of the evaluated preparations increased the RGR values to the greatest degree in the early stages of growth in comparison with the successive phases of development. In the period from sowing to flowering, the greatest increase in the RGR index induced by the spray with the LCO preparations, microelements, and LCOs together with microelements was observed, i.e., 15.0, 15.5, and 24.6%, respectively, in the above-ground parts and 17.9, 18.3, and 36.2%, respectively, in the roots.
The foliar application of the Nod factors or the microelements increased the seed yield, the number of pods per plant, and the number of seeds per plant (Table 6).
The changes induced by the preparations in the pea yield and yield components were determined by the treatment type and the application method (separately or in combination). The highest seed yield was noted in the treatments sprayed with the Nod factors only and with both preparations. The seed yield was significantly lower when the plants were sprayed only with the microelements.
The increase in the seed yield induced by the foliar application of the Nod factors only, the microelements only, and both preparations reached 22.4%, 14.1%, and 32.3%, respectively. This can be attributed mainly to the higher number of pods per plant and the higher number of seeds per plant because the 1000-seed weight and the number of seeds per pod did not change significantly.

4. Discussion

The use of rhizobial Nod factors is one of the methods stimulating the signaling in Rhizobium–legume symbioses. Besides the beneficial effect on nodulation, this treatment can affect plant physiology, resulting in improved germination, photosynthesis, and growth of plants [12,39,40,41,42,43,44]. An increase in legume yield after application of Nod factors has been reported as well [11,12,14,37,45,46]. In most of these cases, Nod factors were used as seed dressing [11,12,14,46], similarly to the traditional rhizobial inoculants containing live bacterial cells. In this study, we examined the effect of Nod factors combined with microelements on pea growth and yield, and this final effect was achieved due to changes in numerous morphological and physiological parameters. Given that symbiosis and plant growth can also be stimulated by foliar application of LCOs [45,46], foliar spraying with LCOs and/or ME was used in the current experiments to reduce the labor intensity of the treatments. This seems to be a procedure that could be more economically justified for field applications of such products.
The number and total mass of nodules are important factors affecting pea yield. The number and mass of nodules were significantly correlated in all the experimental groups (Figure 1). What is more, the significant correlations between the dry mass of nodules and the pea yield or between the number of nodules and the pea yield confirm the importance of symbiotic interactions for plant yield (Figure 2 and Figure 3).
As presented previously [37], the application of LCOs significantly increased the number and mass of root nodules. This finding is in agreement with the knowledge of the mode of action of Nod factors and the direct relationship between the presence of LCOs in the environment and the initiation of formation of root nodules [7].
Interestingly, an increase in the number of root nodules was observed at flowering, also after the application of microelements alone. In this case, the relationship is not as simple as in the case of LCOs. However, it is well known that microelements play a very important role both in numerous processes related to the growth and development of legumes, as well as those responsible for the proper development and efficient functioning of rhizobia–legume symbiotic systems [47,48,49]. There are papers indicating a relationship between specific microelement supplementation and legume nodulation. Even though these papers do not focus on mechanisms of action, the increased number of nodules was reported after application of Mo [18,50,51], Fe [52], B [52,53], or Zn [54]. Moreover, it was shown that copper supplementation increased the mass of nodules [55], the application of molybdenum resulted in the prevention of nodule senescence [56,57], and iron was very important during nodule development initiation [58].
Application of microelements resulted not only in increased nodulation but also in an increase in the net photosynthetic rate. This is consistent with literature data, which reports that individual microelements can improve selected photosynthetic parameters. Experiments conducted on various models have shown that the application of B [59] and Cu [60] increases chlorophyll content, the application of Fe [61] or Zn [62] increases the net photosynthetic rate, and the application of Fe additionally improves electron and energy transport of the photosystems [63]. Therefore, treatment of plants with a microelement mixture alone (without LCOs) also seems justified, and might be responsible for increased nodulation and increased photosynthetic efficiency of plants.
A significant increase in pea mass accumulation and yield was observed after the combined treatment of the plants with the Nod factors and the microelements, which may have been caused by the improvement of numerous physiological parameters. For example, SPAD values, which can be considered as an indicator of plant nitrogen supply [64], reached the highest levels in the LCOs and LCOs-MEs groups. Similarly, after treatment of plants with all tested preparations, the nitrogen content in the above-ground parts of plants (at BBCH-60) as well as in seeds (at BBCH-89) increased significantly, which may be the result of better nodulation of plants and—perhaps—subsequent higher efficiency of symbiotic dinitrogen reduction.
On the other hand, no significant changes were observed in the chlorophyll content (Fm) values, whereas the number of electron acceptors in PSII was increased (area). It could be hypothesized that the significant increase in the pea mass and yield resulted from (a) the good nitrogen supply related to better nodulation, and (b) more effective photosynthesis. Taking into consideration the use of the Fv/Fm ratio as an indicator of nutrient stress [65], it can be concluded that the plants in all the experimental groups did not suffer from such stress, because the Fv/Fm ratios in these groups ranged from 0.817 to 0.828 (a 0.83 value means “no nutrient stress”). Therefore, plant mass accumulation was easier to achieve in the LCOs and LCOs-MEs groups than in the control plants (Fv/Fm ratio: 0.732).
In terms of physiological changes, one alarming parameter was found. All the treatments resulted in increased transpiration (insignificant decrease in WUE values), which may have exposed the plants to water stress. However, the Pindex used for estimation of plant water balance does not support this assumption [43,66]. Since the Pindex values obtained in the plants from the experimental groups were higher than in the control plants, the former seemed to be better supplied with water than the untreated plants, despite the increase in transpiration. Therefore, this decrease cannot be regarded as detrimental, especially when the differences are not significant.
All the physiological effects caused by the application of the Nod factors and/or the microelements resulted in differences in the relative growth rate and pea yield. The LCOs and the LCOs-MEs preparations had a more long-lasting effect (significantly increasing the RGR values until the green pod stage) than the microelements alone, and these two preparations also increased the number of pods per plant, the number of seeds per plant, and the yield of seeds better than the MEs treatment. RGR values calculated for roots were negative in the BBCH75–BBCH89 period for all experimental groups, but this loss can be attributed to the natural process of root decomposition and death, combined with the remobilization of nutrients like nitrogen from older roots to younger parts of the plant or to seeds [67]. The combination of the Nod factors and the microelements had the best effect on the yield of seeds (an increase by 32.3%, compared with the control plants). On the other hand, it is worth noting the role of the microelement treatment: the increase in the seed yield was only 14.1%; however, it affected the growth rate, slowing down decomposition of old roots (from BBCH75 to BBCH90) in the same way as the treatments with LCOs or LCOs-MEs.
The results of the greenhouse experiments presented in this paper indicate that a preparation containing LCOs and MEs may be another complex product beneficial for plant growth and yield. Such a preparation may have a beneficial effect on the acquisition of both nitrogen (thanks to biological nitrogen fixation) and carbon (thanks to photosynthesis). It is known that both these processes are interconnected, both in the short-term biochemical perspective (high nitrogen availability allows for good adaptation of the photosynthesis process to the current lighting conditions [68]) and in the long-term evolutionary perspective (the process of photosynthesis involves a large number of proteins, therefore there is a selection pressure causing the genes encoding these proteins to have such sequences that their transcripts contain as few high N-consuming nitrogen bases as possible [69,70]). Taking into account such relationships, it is worth using a preparation that can (a) stimulate the plant nodulation process with various signals (LCOs and MEs) and thus increase N availability for plants, (b) stimulate in various ways (N availability and MEs) the accumulation of biomass resulting from efficient photosynthesis.
However, it should be noted that the effect of such preparations may depend to some extent on the environmental conditions in which they are used. There are reports of a lack of beneficial effects on plant growth of preparations containing rhizobial LCOs, for example, in cases of severe drought [11] or a long spring wet period [45], so it seems justified to conduct further research on this preparation in multi-year field experiments.

5. Conclusions

  • The Nod factors and microelements significantly influenced selected physiological parameters of yield formation in pea plants (net photosynthetic rate, RGR, and SPAD).
  • The foliar application of the Nod factors and the microelements had a positive influence on the number and weight of root nodules, which was correlated with an increase in the weight of vegetative and generative organs of pea plants.
  • The foliar application of the Nod factors and the microelements significantly enhanced the growth, development, and yield of pea plants, and the treatments were most effective when the studied preparations were used in combination.
  • The increase in the pea yield induced by the LCOs and the microelements can be attributed to the higher number of pods per plant and the higher number of seeds per plant because the number of seeds per pod and the 1000 seed weight did not change significantly.
  • It seems that the simultaneous use of a preparation containing LCOs and microelements has a good synergistic effect. Both (a) an increase in the number of nodules and (b) intensification of metabolic processes were observed, which is probably due to (a) the action of the molecular signal and (b) the provision of numerous cofactors for the most important enzymes and proteins involved in or related to the biological nitrogen fixation process. Nitrogenase activity was not determined; however, a significant increase in nitrogen content in plant tissues was observed after LCOs, ME, or LCOs-ME treatment. As a result, an over 30% seed yield increase was obtained, compared to the control group.
  • The foliar application of both components was fully successful, which is a promising finding, because this method of application is much more time-flexible and convenient than seed dressing.

Author Contributions

Conceptualization, J.P.; methodology, J.P.; validation, J.P. and H.K.; formal analysis, H.K.; investigation, J.P., A.P., and D.K.; resources, J.P.; data curation, H.K.; writing—original draft preparation, J.P., A.P., and J.W.; writing—review and editing, J.W.; visualization, A.P.; supervision, A.P.; project administration, J.P. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Data Availability Statement

The original contributions presented in this study are included in the article. Further inquiries can be directed to the corresponding author.

Conflicts of Interest

The authors declare no conflicts of interest.

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Agronomy 15 02536 g001
Figure 1. Relationship between number and dry weight of root nodules.
Figure 1. Relationship between number and dry weight of root nodules.
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Figure 2. Relationship between number of root nodules and seed yield.
Figure 2. Relationship between number of root nodules and seed yield.
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Figure 3. Relationship between dry weight of root nodules and seed yield.
Figure 3. Relationship between dry weight of root nodules and seed yield.
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Table 1. Chosen morphological features of pea at flowering (BBCH 60).
Table 1. Chosen morphological features of pea at flowering (BBCH 60).
Spraying
Variant		Height of Plants
(cm)		Leaf Area
(cm2 Plant−1)		Number of Leaves
Per Plant
H2O49.2 a *379 a15.4 a
LCOs54.0 b414 b15.7 a
MEs54.7 b394 b14.9 a
LCOs + MEs56.5 b426 b17.6 b
Mean53.6393.215.9
F38.445.113.9
df333
* Results of the LSD range test are shown. Values followed by similar letters in the columns are not significantly different at the 5% probability level.
Table 2. Values of gas exchange parameters at flowering (BBCH 60).
Table 2. Values of gas exchange parameters at flowering (BBCH 60).
Gas Exchange
Parameters and SPAD		 Spraying of Plants MeanFdf
H2OLCOsMEsLCOs + MEs
Pn
(µmol CO2 m−2 s−1)		11.5 a *13.1 c12.8 b13.6 c12.78.383
E
(mmol H2O m−2 s−1)		5.42 a7.23 c6.37 b7.14 c6.5410.13
Gs
(mmol H2O m−2 s−1)		742 a864 b856 b775 a809537.23
WUE
(µmol CO2 mmol−1 H2O)		2.12 a1.81 a2.01 a1.90 a1.967.453
SPAD438 a492 b475 b489 b47342.413
* Results of the LSD range test are shown. Values followed by similar letters in lines are not significantly different at the 5% probability level.
Table 3. Values of chlorophyll fluorescence parameters at flowering (BBCH 60).
Table 3. Values of chlorophyll fluorescence parameters at flowering (BBCH 60).
Chlorophyll
Fluorescence
Parameters		Spraying of PlantsMeanFdf
H2OLCOsMEsLCOs + MEs
Fo576 b *389 a411 a391 a4429.893
Fm2143 a2214 a2246 a2235 a220910.153
Fv/Fm0.732 a0.825 b0.817 b0.825 b0.7992.393
Pindex (PI)4.24 a5.12 b5.23 b5.26 b4.966.613
Tfm580 b530 a540 a530 a5455.673
Area46,100 a52,300 b50,400 b52,600 b50,35081.463
* Results of the LSD range test are shown. Values followed by similar letters in lines are not significantly different at the 5% probability level.
Table 4. Number and dry matter of root nodules and N concentrations in parts of pea plants.
Table 4. Number and dry matter of root nodules and N concentrations in parts of pea plants.
Description Spraying of Plants MeanFdf
H2OLCOsMEsLCOs + MEs
BBCH 60
Number of root nodules
per plant		88.4 a *96.2 b96.5 b105.6 c96.7173.283
Dry matter of root nodules
(mg per plant)		81.1 a90.1 b87.8 b94.4 c88.5145.123
Dry matter of one nodule
(mg)		0.92 a0.94 a0.91 a0.89 a0.910.163
N concentration in
above-ground part (%)		2.31 a2.72 b2.54 c2.71 b2.5717,73
BBCH 75Fdf
Number of root nodules
per plant		74.6 a78.5 ab80.1 ab86.4 b79.985.613
Dry matter of root nodules
(mg per plant)		80.4 a84.4 a84.0 a85.6 a83,618.363
Dry matter of one nodule
(mg)		1.08 a1.08 a1.05 a0.99 a1.051.373
BBCH 90Fdf
N concentration in seeds (%)3.42 a3.84 b3.68 c3.84 b3.6924.43
* Results of the LSD range test are shown. Values followed by similar letters in lines are not significantly different at the 5% probability level.
Table 5. Relative growth rate (RGR) of pea plants [g (g day−1)−1].
Table 5. Relative growth rate (RGR) of pea plants [g (g day−1)−1].
BBCHSpraying of PlantsMeanFdf
H2OLCOsMEsLCOS + MEs
Above-ground part
00–600.448 a *0.515 b0.516 b0.558 b0.51019.243
60–751.579 a1.749 b1.612 a1.742 b1.67154.283
75–891.162 a1.148 a1.124 a1.394 b1.15747.343
Roots Fdf
00–600.224 a0.264 b0.265 b0.305 c0.26516.1
60–750.682 a0.746 b0.668 a0.741 b0.71018.23
75–89−4.619 b−3.213 a−3.140 a−3.026 a−3.5005.93
* Results of the LSD range test are shown. Values followed by similar letters in lines are not significantly different at the 5% probability level.
Table 6. Yield and yield components of pea (BBCH 90).
Table 6. Yield and yield components of pea (BBCH 90).
DescriptionSpraying of Plants MeanFdf
H2OLCOsMELCOs + ME
Number of pods per plant5.08 a *6.14 b5.52 b5.94 b5.6719.113
Number of seeds per pod4.07 a3.70 a3.96 a4.05 a3.940.943
Number of seeds per plant20.7 a22.7 b21.9 b24.1 c22.324.583
Weight of 1000 seeds (g)216 a212 a216 a218 a2152.293
Yield of seeds (g per pot)19.2 a23.5 b21.9 b25.4 c22.565.593
* Results of the LSD range test are shown. Values followed by similar letters in lines are not significantly different at the 5% probability level.
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Podleśny, J.; Wielbo, J.; Podleśna, A.; Klikocka, H.; Kidaj, D. The Influence of Foliar Application of Nod Factors (LCOs) and Microelements on the Growth, Development, and Yield of Peas (Pisum sativum L.). Agronomy 2025, 15, 2536. https://doi.org/10.3390/agronomy15112536

AMA Style

Podleśny J, Wielbo J, Podleśna A, Klikocka H, Kidaj D. The Influence of Foliar Application of Nod Factors (LCOs) and Microelements on the Growth, Development, and Yield of Peas (Pisum sativum L.). Agronomy. 2025; 15(11):2536. https://doi.org/10.3390/agronomy15112536

Chicago/Turabian Style

Podleśny, Janusz, Jerzy Wielbo, Anna Podleśna, Hanna Klikocka, and Dominika Kidaj. 2025. "The Influence of Foliar Application of Nod Factors (LCOs) and Microelements on the Growth, Development, and Yield of Peas (Pisum sativum L.)" Agronomy 15, no. 11: 2536. https://doi.org/10.3390/agronomy15112536

APA Style

Podleśny, J., Wielbo, J., Podleśna, A., Klikocka, H., & Kidaj, D. (2025). The Influence of Foliar Application of Nod Factors (LCOs) and Microelements on the Growth, Development, and Yield of Peas (Pisum sativum L.). Agronomy, 15(11), 2536. https://doi.org/10.3390/agronomy15112536

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