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Article

Physiological and Biochemical Responses of Mentha spp. to Light Spectrum and Methyl Jasmonate in a Controlled Plant Factory Environment

by
Thanyaluk Dangsamer
1,†,
Panita Chutimanukul
2,†,
Siripong Sukdee
1,
Theeraphat Liamjinda
1,
Ornprapa Thepsilvisut
1,
Hiroshi Ehara
3 and
Preuk Chutimanukul
1,*
1
Department of Agricultural Technology, Faculty of Science and Technology, Thammasat University, Khlong Luang, Pathum Thani 12120, Thailand
2
National Center for Genetic Engineering and Biotechnology (BIOTEC), National Science and Technology Development Agency, Khlong Luang, Pathum Thani 12120, Thailand
3
International Center for Research and Education in Agriculture, Nagoya University, Nagoya 464-8601, Japan
*
Author to whom correspondence should be addressed.
†
These authors contributed equally to this work.
Horticulturae 2025, 11(10), 1243; https://doi.org/10.3390/horticulturae11101243
Submission received: 15 September 2025 / Revised: 7 October 2025 / Accepted: 9 October 2025 / Published: 15 October 2025
(This article belongs to the Section Protected Culture)
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Abstract

Peppermint (Mentha spp.) produces bioactive metabolites under stress. Light spectrum and methyl jasmonate (MeJA) are important factors influencing growth, physiology, and antioxidant defense. In this study, peppermint was cultivated under different light spectra and foliar MeJA concentrations in a controlled environment. Plants exposed to a balanced RGB (1:1:1) spectrum showed the greatest morphological development, with plant height (35.99 cm), canopy width (21.24 cm), and chlorophyll content (29.64 SPAD) significantly higher than those in other treatments. Foliar application of MeJA produced concentration-dependent effects: 2.0 mM increased photosynthetic rate to 6.49 µmol m−2 s−1 compared with 4.52 µmol m−2 s−1 in the control, 2.5 mM resulted in the highest fresh and dry biomass (24.82 g/plant and 2.42 g/plant, respectively), and 1.5 mM yielded the highest total phenolics (20.22 mg GAE/g DW) and antioxidant activity (60.97%). These findings demonstrate that peppermint responses to MeJA are strongly dose dependent and that light quality modulates growth by reducing stress compared with monochromatic spectra. Overall, the results suggest that integrating balanced light spectra with optimized MeJA concentrations can improve both biomass and secondary metabolite accumulation, supporting peppermint production under controlled conditions.

1. Introduction

Peppermint (Mentha spp.), a member of the Lamiaceae family, originates from the southern Europe and the Mediterranean region. It has gained global recognition due to its essential oils and bioactive compounds, which exhibit antimicrobial, antibacterial, antioxidant, antispasmodic, digestive, and analgesic activities [1]. The major constituents of peppermint, including menthol, menthone, isomenthone, methyl acetate, and cineol, contribute to its distinct aromatic profile and therapeutic efficacy, which is reflected in its widespread application in aromatherapy for its cooling and relaxing effects [2,3]. Due to its pharmacological properties, peppermint is increasingly valued in the pharmaceutical and cosmeceutical industries and has strong potential as a high-value export crop. Nevertheless, peppermint cultivation in Thailand remains limited, primarily due to its vulnerability to pests and diseases such as rust, root and stem rot, leaf miners, aphids, and mealybugs, as well as environmental fluctuations and restricted access to advanced cultivation technologies [4,5]. Conventional open-field cultivation is limited by environmental variability and genetic instability, which reduce growth, yield, and metabolite accumulation. Peppermint is particularly sensitive to abiotic stresses (drought, heat, salinity, and light) and biotic stresses (pests and pathogens), which, while constraining productivity, also activate defense pathways that enhance photosynthesis, antioxidant capacity, and secondary metabolite synthesis. Thus, managing these stress responses is essential to improve peppermint’s resilience, yield, and phytochemical quality.
Plant factory technology has recently emerged as a multidisciplinary platform for advancing crop production under fully controlled environmental conditions. These systems not only enable precise management of growth parameters such as temperature, humidity, nutrient supply, and CO2 concentration, but also allow the application of targeted environmental cues that act as abiotic stresses to shape plant performance [6]. Among these, light spectrum, intensity, and photoperiod represent key regulatory factors that profoundly influence plant growth, photosynthesis, and secondary metabolism. Artificial lighting, particularly light-emitting diodes (LEDs), has gained prominence as a controllable stressor due to its high energy efficiency, spectral precision, and extended operational life [7]. The choice of light wavelengths and color combinations is especially important, as these parameters significantly affect photosynthetic efficiency, morphogenesis, and the biosynthesis of secondary metabolites [8,9]. Red (600–700 nm) and blue (400–500 nm) light are the principal wavelengths absorbed by plants for photosynthesis and chlorophyll synthesis, with the most effective ranges reported between 400 and 480 nm and between 630 and 680 nm [10,11,12]. Compared with conventional lighting systems, LEDs provide substantial advantages by delivering tailored spectra to optimize plant growth, improve functional quality, and reduce production costs [7]. Consequently, in plant factory systems, light quality should be regarded not only as a fundamental input for biomass accumulation but also as a strategic tool for stress management to enhance resilience and metabolic performance. This perspective highlights artificial light–induced stress as a sustainable approach for improving plant productivity and adaptive traits in controlled environment agriculture.
Beyond environmental factors such as light, the biosynthesis of plant secondary metabolites is also regulated by chemical stress signals, notably the exogenous application of methyl jasmonate (MeJA). Functioning as a stress-related phytohormone, MeJA activates defense mechanisms such as the phenylpropanoid pathway by stimulating phenylalanine ammonia-lyase (PAL) activity, thereby promoting the accumulation of phenolic compounds with strong antioxidant properties [13,14]. The interaction between light quality and jasmonate signaling exemplifies how abiotic and chemical stressors can be strategically integrated to enhance plant growth and metabolic performance. Based on this premise, the present study explores the combined effects of light spectrum and MeJA concentration on growth, physiological responses, and antioxidant activity in peppermint (Mentha spp.) cultivated under controlled environmental conditions. By elucidating these stress-induced responses, the research aims to establish optimized strategies that balance biomass production with the enhancement of secondary metabolites. Ultimately, the findings are expected to support the development of stress-based cultivation approaches for high-value medicinal plants, thereby improving functional quality and strengthening their industrial applicability in controlled environment agriculture. Although some studies have examined the effects of MeJA or light quality in peppermint, such research remains limited and rarely addresses their combined impact under controlled conditions. Therefore, this study investigated the interactive effects of light spectrum and MeJA concentration on peppermint growth, physiology, and antioxidant capacity, aiming to develop stress-based strategies that balance biomass yield with enhanced secondary metabolites. In this context, controlled environment agriculture combined with targeted stress management strategies, such as optimized light spectra and foliar application of MeJA, may provide practical solutions to overcome pest and disease pressures as well as environmental variability in peppermint cultivation. Such approaches highlight the potential of stress-based cultivation to improve peppermint resilience and productivity under controlled conditions.

2. Materials and Methods

2.1. Investigation of the Effects of Light Spectra on the Growth of Peppermint Under Controlled Environmental Conditions

2.1.1. Plant Material and Growth Conditions

Peppermint seeds (Mentha spp., Three A brand) were germinated on sponge cubes under controlled conditions consisting of a photosynthetic photon flux density (PPFD) of 150 µmol m−2 s−1, a 16 h photoperiod, air temperature of 25 ± 1.5 °C, and relative humidity of 70 ± 5%. After 7 days, seedlings that had developed true leaves and roots were transferred to a deep flow technique (DFT) hydroponic system, modified from the method of Shinohara et al. [15]. The system was supplied with a modified Enshi nutrient solution (EC 2.10 mS/cm, pH 6.5). Plants were subsequently cultivated in an indoor vertical farm at the National Science and Technology Development Agency (NSTDA), Thailand, under LED lighting (150 µmol m−2 s−1, 16 h light period), air temperature of 25 ± 1 °C, relative humidity of 70 ± 1%, and CO2 concentration of 1000 ± 100 ppm.

2.1.2. Spectral Light Conditions

In this study, the light spectrum setup was adapted from the procedure of Chutimanukul et al. [16]. The illumination was provided by LED arrays (AGRI-OPTECH Co., Ltd., Tainan, Taiwan) capable of producing three wavelength ranges—red (R, 600–700 nm, peak at 660 nm), blue (B, 400–500 nm, peak at 450 nm), and green (G, 500–600 nm, peak at 525 nm). Peppermint seedlings were grown under five spectral light regimes with distinct ratios of R:G:B: (L1) 1:1:1 (33.33:33.34:33.33), (L2) 2:1:2 (40:20:40), (L3) 1:1 (50:50), (L4) 1:3 (25:75), and (L5) 3:1 (75:25). The LED units were positioned 40 cm above the plants to ensure even light distribution across the growth area. The spectral characteristics and photosynthetic photon flux density (PPFD) of each treatment were assessed using a spectroradiometer (LI-180, LI-COR Inc., Lincoln, NE, USA) and validated with a light analyzer (C-7000, Sekonic, Tokyo, Japan). All treatments were maintained at a constant PPFD of 150 µmol m−2 s−1 throughout the experiment to provide uniform light intensity across the spectral treatments (Figure 1 and Figure S1).

2.1.3. Plant Growth Measurements

Plant growth parameters were assessed at 42 days after transplanting (DAT). Plant height and canopy width were measured using a standard ruler, from the base to the apical tip and across the widest canopy span, respectively. Leaf area was determined with a portable laser leaf area meter (Model CI-202, CID Bio-Science, Camas, WA, USA). The number of leaf pairs was manually counted along the main stem. Chlorophyll content was quantified using a SPAD-502 Plus chlorophyll meter (Konica Minolta, Tokyo, Japan) on the third fully expanded leaf from the shoot apex. Fresh and dry weights of leaves and stems were recorded using an analytical balance (Model TX2202L, Shimadzu, Kyoto, Japan). Dry weights were measured after oven-drying the samples at 50 °C for 72 h.

2.2. Effects of Foliar-Applied Methyl Jasmonate Under Selected Light Spectrum

2.2.1. Plant Material and Growth Conditions

The preparation of seedlings followed the method described in Section 2.1.1.

2.2.2. Cultivation and Treatment

Seedlings were transplanted into the DFT system as described previously. The optimal light spectrum was identified from Section 2.1. (1R:1G:1B) was applied. Foliar application of MeJA was performed three days before harvest using concentrations of 0 (control), 0.5, 1.0, 1.5, 2.0, and 2.5 mM.

2.2.3. Plant Growth Measurements

The parameters evaluated were the same as those described in Section 2.1.3.

2.2.4. Physiological Measurements

Physiological traits were evaluated 42 days after transplanting (DAT) to determine the photosynthetic rate (A), transpiration (E), stomatal conductance (gsw), and intercellular CO2 concentration (Ci). Measurements were taken using a portable photosynthesis system (LI-6800, LI-COR Inc., Lincoln, NE, USA) equipped with a 3 cm2 circular chamber. The operating settings were maintained at an airflow of 500 mmol m−2 s−1 per leaf area, leaf temperature of 25 °C, 70% relative humidity, and 1000 µmol mol−1 CO2 concentration. Light inside the chamber was adjusted to a photosynthetic photon flux density (PPFD) of 150 µmol m−2 s−1, and readings were collected from a fully expanded mature leaf.

2.2.5. Secondary Metabolite Quantification

  • Sample extraction
After harvest (42 DAT), all peppermint samples were oven-dried at 50 °C for 72 h and finely ground using a mortar and pestle. Extraction was performed using a modified protocol described by Chutimanukul et al. [16]. Approximately 10 mg of powdered tissue was mixed with 5 mL of methanol containing 1% HCl in a 15 mL centrifuge tube. The suspension was vortexed thoroughly for homogenization and incubated at room temperature for 3 h. After incubation, it was centrifuged at 8500 rpm for 8 min using an Eppendorf 5810R centrifuge (rotor F-34 6-38, 6 × 125 g, Eppendorf SE, Hamburg, Germany). The resulting supernatant was collected in 1.5 mL microtubes and subsequently used for the determination of total phenolic content, flavonoids, anthocyanins, and DPPH radical scavenging activity.
  • Determination of total phenolic compounds (TPC)
Total phenolic content (TPC) was quantified using a modified Folin–Ciocalteu method adapted from Chutimanukul et al. [17]. A 200 µL aliquot of the extract was combined with an equal volume of 1 N Folin–Ciocalteu reagent and vortexed, followed by centrifugation at 10,000 rpm for 2 min and incubation for 15 min at room temperature. Subsequently, 600 µL of 7.5% sodium carbonate (Na2CO3) was added, mixed thoroughly, and centrifuged again at 10,000 rpm for 2 min. After a 1 h incubation, the absorbance of the reaction mixture was measured at 730 nm using a microplate reader (Multiskan Sky, Thermo Scientific, Waltham, MA, USA). TPC was calculated based on a gallic acid standard curve prepared from concentrations of 0–250 µg/mL (250, 125, 62.5, 31.25, 15.63, 7.8, 3.9, 1.9, and 0.97 µg/mL). Results were expressed as milligrams of gallic acid equivalent (mg GAE) per gram of sample dry weight (DW).
  • Determination of flavonoid content
The quantification of flavonoid content was determined using a modified colorimetric procedure based on Chutimanukul et al. [17]. In brief, 350 µL of the extract was combined with 75 µL of 5% sodium nitrite (NaNO2) in a 1.5 mL microtube and centrifuged at 10,000 rpm for 2 min. The mixture was left to stand at 25 °C for 5 min, followed by the addition of 75 µL of 10% aluminum chloride (AlCl3·6H2O) and centrifugation again under the same conditions. After another 5 min incubation, 500 µL of 1 M sodium hydroxide (NaOH) was introduced, vortexed to ensure uniform mixing, and then centrifuged for 2 min at 10,000 rpm. The reaction mixture was allowed to stand for 15 min, and the absorbance was subsequently recorded at 515 nm using a microplate reader (Multiskan Sky, Thermo Scientific, Waltham, MA, USA). The quantification of flavonoid content was quantified using a calibration curve prepared from rutin standards dissolved in dimethyl sulfoxide (DMSO) and expressed as milligrams of rutin equivalent (mg Ru) per gram of dry weight (DW).
  • DPPH radical scavenging activity
The antioxidant activity of peppermint extracts was determined using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay, adapted from Chutimanukul et al. [17]. Briefly, 100 µL of extract was transferred to a 1.5 mL microtube and mixed with 900 µL of 0.1 mM DPPH solution. The reaction mixture was vortexed for uniform blending and centrifuged at 10,000 rpm for 2 min. Samples were then incubated in the dark at 25 °C for 3 h, during which the color gradually changed from purple to yellow. The absorbance was subsequently recorded at 515 nm using a microplate reader (Multiskan Sky, Thermo Scientific, Waltham, MA, USA). The percentage of DPPH radical scavenging activity was calculated using the following equation:
% DPPH   inhibition   =   absorbance   of   control − absorbance   of   sample absorbance   of   control × 100
  • Determination of Anthocyanin content
The determination of anthocyanin content was carried out following a modified protocol described by Chutimanukul et al. [17]. Briefly, 500 µL of the extract was combined with 400 µL of deionized water and 400 µL of chloroform in a microtube. The mixture was vortexed gently and centrifuged at 10,000 rpm for 5 min at 25 °C to separate the phases. The upper aqueous layer was collected, and its absorbance was recorded at 515 nm and 657 nm using a microplate reader (Multiskan Sky, Thermo Scientific, Waltham, MA, USA). The anthocyanin concentration was then calculated using the following equation:
Anthocyanin   =   A 530 − ( 0.33 × A 657 )

2.3. Statistical Analysis

The experimental data were analyzed using one-way analysis of variance (ANOVA), and mean separations were performed with Duncan’s multiple range test (DMRT) at a significance level of p < 0.05. All statistical analyses were carried out with IBM SPSS Statistics version 21 (IBM Corporation, Armonk, NY, USA).

3. Results and Discussion

3.1. Effects of Light Spectrum on the Growth of Peppermint Under Controlled Environmental Conditions

3.1.1. Plant Growth

The effects of different light spectra on peppermint growth under controlled conditions showed that the 1R:1G:1B spectrum produced the most favorable outcomes. Plants grown under this treatment exhibited the greatest plant height (35.99 cm), canopy width (21.24 cm), leaf area (16.18 cm2), and chlorophyll content (29.64 SPAD units) (Table 1). These results confirm that spectral composition plays a critical role in shaping growth performance. Red light is known to promote fresh and dry biomass accumulation, stem elongation, and leaf expansion [18,19,20]. It is relatively low energy and high absorption efficiency stimulates stem elongation, particularly through the activation of indole-3-acetic acid (IAA), which regulates cell elongation [21]. When combined with a small proportion of blue light, growth performance is further enhanced [22]. This trend aligns with the findings of Tabbert et al. [23] and Dou et al. [24], who reported that a combination of red, green, and blue light resulted in taller plants with wider canopies compared to other mixed light treatments. The inclusion of green light also facilitates deeper light penetration to lower leaves, mimicking natural light conditions [25] as red and blue light are mostly absorbed by the upper leaves [24]. Similarly, Wang et al. [26] demonstrated that neither red nor blue light alone was sufficient to maximize development, whereas balanced spectral combinations significantly improved overall growth. The enhanced leaf area observed under the 1R:1G:1B treatment can be attributed to red light stimulating cell expansion, blue light promoting leaf morphology and chlorophyll biosynthesis, and green light further supporting expansion when combined with red and blue wavelengths [27]. Green light, although less efficiently absorbed, also contributes to leaf expansion, especially when used in combination with red and blue light at appropriate ratios. There were no statistically significant differences in the number of leaf pairs across treatments, as this characteristic is more strongly influenced by genetic factors, temperature, humidity, and nutrient availability than by light spectrum alone [28]. While red and blue light regulate plant growth through photoreceptors and phytohormones such as auxins and cytokinins, they do not directly increase leaf number [29]. The significantly higher SPAD values under the 1R:1G:1B spectrum indicate improved photosynthetic efficiency and chlorophyll production. Blue light enhances chlorophyll biosynthesis and leaf development, red light stimulates cell expansion and flowering, and green light, despite its lower absorption efficiency, penetrates deeper into the canopy to stimulate photosynthesis in lower leaves [25]. These findings are consistent with Hogewoning et al. [30], which indicated that a combination of multiple light spectra increases chlorophyll content and photosynthetic efficiency more effectively than monochromatic light.
From a stress biology perspective, light functions not only as a regulator of plant growth but also as an abiotic stressor that influences physiological and metabolic responses. Monochromatic light, such as red or blue alone, can induce stress by disrupting photosynthesis, altering hormone signaling, and reducing chlorophyll synthesis. Conversely, a balanced mixture of red, green, and blue wavelengths provides a moderated stress environment that enhances adaptive responses, leading to improved photosynthetic efficiency, chlorophyll accumulation, and secondary metabolite biosynthesis. These findings highlight that light quality can be strategically managed both as a growth regulator and as a controlled stress factor to improve peppermint’s resilience, productivity, and functional quality in controlled cultivation systems.

3.1.2. Biomass Accumulation

A study on the effects of different light spectra on the fresh and dry weights of peppermint leaves and stems revealed statistically significant differences among treatments. The 1R:1G:1B light spectrum resulted in the highest fresh weights of both leaves (11.21 g/plant) and stems (11.60 g/plant). In contrast, the lowest values were observed under the 3R:1B spectrum, yielding 7.29 g/plant for leaves and 6.69 g/plant for stems. Similarly, the 1R:1G:1B spectrum produced the highest dry weights of leaves (1.05 g/plant) and stems (0.86 g/plant), while the 3R:1B spectrum resulted in the lowest dry leaf weight (0.56 g/plant). Although the 1R:1B (0.69 g/plant) and 2R:1G:2B (0.71 g/plant) spectra produced similar dry leaf weights, they were still lower than those under the 1R:1G:1B treatment. Additionally, the lowest dry stem weight (0.41 g/plant) was recorded under the 2R:1G:2B spectrum (Table 2). Different light spectra regulate peppermint’s stress responses by activating photoreceptors (phytochromes, cryptochromes, phototropins), which influence photosynthesis, hormone signaling, and secondary metabolism. Red light promotes stem elongation and biomass accumulation, while blue light enhances chlorophyll synthesis and antioxidant defense. Green light, on the other hand, penetrates deeper into the canopy to support photosynthesis in lower leaves. An unbalanced spectrum can generate excess reactive oxygen species (ROS), causing stress, whereas a balanced 1R:1G:1B spectrum provides moderated stress that stimulates adaptive responses, leading to improved growth [31]. These results are consistent with those of Chutimanukul et al. [16], who found that white holy basil grown under a 2R:1G:2B spectrum produced greater dry biomass compared to plants under 1R:1B and 1R:3B spectra. Similarly, green light has been shown to enhance photosynthetic activity more effectively than red or blue light alone [32]. Supplementing lettuce with green light, in addition to red and blue, has been shown to improve photosynthetic capacity and chlorophyll content. Smith et al. [33] further recommend incorporating more green light in LED systems to increase biomass accumulation and overall productivity. Taken together, the 1R:1G:1B light spectrum appears to be the most effective light quality for promoting peppermint growth under controlled environmental conditions. In the context of plant stress biology, light quality can act as both a growth driver and an abiotic stressor. Unbalanced spectra, such as excessive red or blue light, may impose stress that limits photosynthesis and biomass accumulation. In contrast, the balanced 1R:1G:1B spectrum provides a moderated stress environment that enhances adaptive responses, resulting in greater fresh and dry biomass. This highlights the role of optimized light spectra in managing stress to improve peppermint growth and productivity in controlled systems.

3.1.3. Correlation Analysis of the Light Spectrum on the Growth of Peppermint

Correlation analysis was conducted to evaluate the relationships among growth parameters of plants cultivated under five different light spectrum treatments (1R:1G:1B, 2R:1G:2B, 1R:1B, 1R:3B, and 3R:1B). The variables included plant height, canopy width, leaf area, number of leaf pairs, SPAD unit, and the fresh and dry weights of both leaves and stems. The results revealed strong positive correlations between morphological traits (plant height, canopy width, and leaf area) and biomass-related parameters (fresh and dry weights of leaves and stems). Specifically, canopy width and leaf area exhibited correlation coefficients above 0.75 with fresh and dry leaf weights, indicating that larger canopy development was strongly associated with higher leaf biomass. Similarly, plant height was moderately correlated with stem biomass, suggesting that vertical growth contributes significantly to stem accumulation. SPAD values, which represent chlorophyll content, were positively correlated with leaf area (r > 0.80) and plant height (r > 0.85), implying that increased leaf expansion and plant height are linked with enhanced photosynthetic capacity. In contrast, the number of leaf pairs showed only moderate correlations with canopy width and leaf area (r ≈ 0.40–0.70), and weak associations with SPAD values, suggesting that leaf count alone may not adequately reflect photosynthetic performance or biomass accumulation. Additionally, strong correlations were observed between fresh and dry weights of both leaves and stems (r > 0.90), reflecting the expected relationship between fresh tissue mass and dry matter content (Figure 2).
These findings indicate that light spectrum treatments influence multiple growth parameters simultaneously, with strong interdependence among structural traits, chlorophyll content, and biomass production. These findings highlight the strong interdependence among structural growth, chlorophyll content, and biomass under different light spectra, and suggest that specific combinations of red, green, and blue light may enhance growth efficiency by simultaneously promoting morphological development and photosynthetic capacity, which is consistent with previous studies reporting [16] that optimized RGB ratios improve both biomass accumulation and physiological performance in controlled environments. From the results of experiment 2.1, it was found that the 1R:1G:1B light spectrum had the most significant influence on peppermint growth, resulting in the highest growth. Therefore, this light spectrum was applied in the subsequent experiment described in Section 2.2.

3.2. Effects of Foliar Application of Methyl Jasmonate at Different Concentrations on Peppermint Under a 1R:1G:1B Spectrum

3.2.1. Plant Growth

The study investigated the effects of foliar application of MeJA at different concentrations on the growth of peppermint under a controlled 1R:1G:1B light spectrum. Results showed significant enhancement in plant height, with 2.0 mM MeJA yielding the tallest plants at 36.16 cm, followed by 0.5, 1.0, 1.5, and 2.5 mM treatments, while the control (0 mM) had the shortest height of 28.65 cm, indicating MeJA’s role in promoting stem elongation Via cell expansion and growth regulation [34,35]. Canopy width was maximized at 1.5 and 2.0 mM (35.13 and 34.20 cm, respectively), with lower or higher concentrations showing reduced effects, consistent with MeJA’s function in gene expression related to branching and secondary metabolite synthesis [36,37,38]. Leaf area peaked at 2.0 mM (26.95 cm2) and slightly decreased at 2.5 mM (Figure 3; Table 3), while lower concentrations had less effect, reflecting MeJA’s regulatory role in cell expansion and protein synthesis for leaf development [36,37,39]. The highest number of leaf pairs was observed at 2.5 mM MeJA (8.16 pairs), indicating enhanced cell division and leaf development, aligned with MeJA’s influence on growth-related gene expression and secondary metabolite production [40]. Chlorophyll content (SPAD unit) showed no significant difference across treatments (31.89–34.10), suggesting MeJA did not directly affect chlorophyll synthesis, possibly acting through other physiological pathways (Table 3). Overall, these findings highlight the concentration-dependent effects of MeJA on peppermint growth parameters under the 1R:1G:1B spectrum, emphasizing its role as a growth regulator that can optimize morphological traits up to an optimal concentration, beyond which growth inhibition may occur due to hormonal or oxidative stress [34,35,38]. From a stress physiology perspective, MeJA functions as a chemical stress signal that modulates peppermint growth and development. While optimal concentrations (around 1.5–2.0 mM) stimulate adaptive responses such as stem elongation, canopy expansion, and leaf development, higher concentrations can impose excessive stress, leading to growth inhibition through hormonal imbalance or oxidative pressure. This demonstrates how MeJA acts as both a beneficial elicitor and a potential stressor, depending on its dosage, and highlights the importance of optimizing stress levels to maximize peppermint’s growth and resilience. In this study, MeJA was applied only three days before harvest, which likely influenced short-term physiological processes rather than inducing substantial long-term changes in growth traits. This limitation should be acknowledged, and future studies should evaluate longer-term or repeated applications better to clarify the cumulative effects on growth and biomass production.

3.2.2. Biomass Accumulation

The study on fresh and dry weights of leaves and stems of peppermint treated with foliar applications of MeJA at varying concentrations under a combined light spectrum ratio of 1R:1G:1B revealed statistically significant differences among treatments. Application of MeJA at a concentration of 2.5 mM resulted in the highest fresh weights of leaves and stems, at 24.82 g/plant and 22.28 g/plant, respectively. Similarly, the highest dry weights of leaves and stems were recorded at 2.42 g/plant and 1.70 g/plant, respectively, under the same concentration. These values were significantly greater than those obtained from lower concentrations (0.5 and 1.0 mM), which showed the lowest fresh and dry biomass (Table 4). These findings indicate that MeJA at higher concentrations enhances plant growth by promoting cell division, cell expansion, and nutrient biosynthesis [41,42]. The results align with previous studies by Zaid and Mohammad [43], who reported that MeJA combined with nitrogen improved dry weight and physiological structure in Mentha arvensis under cadmium stress. However, these findings contrast with those of Li et al. [44], who observed reduced growth and dry weight in sunflower, tomato, and soybean when treated with 2.5 mM MeJA, suggesting that the growth response may vary depending on plant species [43,44]. In the context of plant stress biology, MeJA functions as an abiotic stress signal that can enhance or inhibit growth depending on concentration and plant species. In peppermint, higher concentrations such as 2.5 mM induced beneficial stress that stimulated biomass accumulation through enhanced cell division and metabolic activity. However, excessive or species-specific sensitivity to MeJA may trigger negative stress responses, leading to growth inhibition, as reported in other crops. These findings highlight the dual role of MeJA as both a growth-promoting elicitor and a stressor, underscoring the need for precise optimization in stress management strategies for peppermint cultivation.

3.2.3. Correlation Analysis of the MeJA Concentrations on the Growth of Peppermint

Correlation analysis of peppermint plants exposed to different concentrations of methyl jasmonate (MeJA; 0, 0.5, 1.0, 1.5, 2.0, and 2.5 mM) revealed distinct relationships among morphological, physiological, and biomass-related traits. Plant height showed a strong positive correlation with leaf area (r > 0.90) and a moderate correlation with stem biomass, indicating that vertical growth was closely associated with leaf expansion and structural development. Canopy width also correlated positively with biomass traits, particularly with dry leaf weight (r ≈ 0.65), suggesting that wider canopies supported greater biomass accumulation. The number of leaf pairs exhibited strong correlations with both fresh and dry weights of leaves and stems (r ≈ 0.85–0.94), highlighting its predictive value for overall biomass production. In contrast, SPAD values (chlorophyll content) showed only weak to moderate correlations with growth traits and biomass, suggesting that chlorophyll concentration alone was not a direct determinant of biomass accumulation under MeJA treatments. Fresh and dry weights of both leaves and stems were highly correlated (r > 0.95), confirming that increases in fresh mass strongly reflected dry matter accumulation (Figure 4).
These results indicate that the application of MeJA influenced peppermint growth and biomass production through coordinated changes in morphological traits. The strong correlations between plant height, leaf area, and biomass suggest that MeJA-induced growth stimulation was tightly linked to enhanced leaf expansion, which may improve photosynthetic surface area. The significant association between leaf number and biomass further supports the role of structural development in determining yield potential. Interestingly, SPAD values showed only limited correlation with biomass, implying that chlorophyll content was not the primary driver of growth under MeJA application, but rather a secondary physiological response. Overall, these findings suggest that moderate concentrations of MeJA can enhance peppermint biomass by promoting morphological traits such as leaf expansion and canopy development, while its effect on chlorophyll content appears less pronounced.

3.2.4. Physiological Responses

Under a combined light spectrum ratio of 1R:1G:1B, foliar application of MeJA at varying concentrations significantly influenced the physiological responses of peppermint. The photosynthetic rate reached its maximum at 2.0 mM (6.49 µmol m−2 s−1), significantly higher than the control (4.52 µmol m−2 s−1), indicating enhanced CO2 assimilation as a result of stomatal opening and improved light-use efficiency [44,45,46]. Similarly, transpiration rates peaked at 1.5–2.0 mM (3.06–3.15 mmol m−2 s−1) (Figure 5A,B), suggesting increased water vapor exchange, possibly driven by changes in stomatal density and epidermal structure [44]. Stomatal conductance also followed a similar trend, with the highest value (0.32 mol m−2 s−1) at 2.0 mM (Figure 5C), reflecting the compound’s role in regulating gas exchange mechanisms through concentration-dependent stomatal modulation [28,47,48]. However, at 2.5 mM, a slight decline in photosynthetic activity and stomatal conductance was observed, possibly due to oxidative stress or excessive stomatal closure under high elicitor concentrations [49]. Interestingly, intercellular CO2 concentrations remained statistically unaffected across treatments (937.90–944.17 µmol mol−1), indicating that physiological improvements stemmed not from increased CO2 availability but from enhanced CO2 utilization efficiency and regulatory mechanisms independent of internal CO2 accumulation. Overall, MeJA at optimal concentrations, particularly 2.0 mM, positively regulates multiple physiological processes, optimizing photosynthetic performance and transpiration dynamics in pepperment under controlled light environments (Figure 5D; Table S1). Viewed through the lens of stress physiology, MeJA acts as a signaling molecule that modulates peppermint’s physiological performance under controlled light environments. Optimal concentrations (around 2.0 mM) triggered beneficial stress responses, enhancing stomatal regulation, photosynthetic efficiency, and transpiration. However, higher levels such as 2.5 mM appeared to impose excessive stress, likely through oxidative pressure or stomatal restriction, leading to reduced gas exchange. These findings underscore the dual role of MeJA-induced stress as both a stimulator of adaptive physiological responses and a potential inhibitor when applied beyond the plant’s tolerance threshold.

3.2.5. Secondary Metabolite Quantification

A study on the effects of foliar application of MeJA on secondary metabolite synthesis and antioxidant activity in peppermint under a 1R:1G:1B light spectrum revealed that MeJA concentration significantly influenced the accumulation of bioactive compounds. The optimal response was observed at 1.5 mM MeJA, which resulted in the highest total phenolic content (20.22 mg GAE/g DW) (Figure 6A) and antioxidant activity (60.97%) (Figure 6C). The maximum flavonoid content (12.33 mg Rutin/g DW) was recorded at 1.0 mM MeJA (Figure 6B), while the highest anthocyanin content (0.15 µg/g DW) was found at 2.5 mM (Figure 6D; Table S2). These results indicate a dose-dependent response, where appropriate MeJA concentrations can upregulate the expression of genes involved in secondary metabolite biosynthesis, such as PAL in the phenylpropanoid pathway [50,51], and through jasmonate-responsive elements (JREs), which regulate flavonoid-related gene expression [52]. Moreover, MeJA induces the activity of antioxidant enzymes, including SOD, CAT, and POD [53,54], enhancing the plant’s ability to mitigate oxidative damage caused by reactive oxygen species (ROS). However, excessively high MeJA concentrations, such as 2.5 mM, may trigger oxidative stress, subsequently suppressing the production of phenolics and antioxidant compounds [55,56]. Several previous studies support these findings: Kim et al. [45] demonstrated that MeJA at 0.25–0.5 mM enhanced phenolic synthesis in romaine lettuce; Kandoudi et al. [57] reported that 2.0 mM MeJA increased phenolics, flavonoids, and essential oils in Mentha piperita L.; Afkar [58] found that 0.1 mM MeJA significantly boosted phenolics in mint; and Abdi et al. [59] showed increased flavonoids and antioxidant activity in Mentha piperita L. under drought stress following MeJA treatment. Similarly, Wang et al. [60] observed an increase in flavonoids in blackberries due to MeJA. Furthermore, Talebi et al. [61] confirmed that MeJA stimulated secondary metabolite production in basil under salt stress conditions, underscoring MeJA’s potential to enhance the phytochemical quality of medicinal plants under challenging environments. From the perspective of plant stress responses, MeJA functions as a chemical elicitor that mimics stress signals, activating defense pathways and secondary metabolism in peppermint. When combined with controlled light spectra such as 1R:1G:1B, these stress cues synergistically enhance phenolic, flavonoid, and antioxidant accumulation by regulating both enzymatic activity and gene expression. However, excessive elicitation at higher concentrations can shift from beneficial stress to oxidative stress, suppressing metabolite synthesis. This highlights how optimizing stress intensity through both light quality and MeJA application can be leveraged to improve peppermint’s resilience and phytochemical quality under controlled cultivation systems. A limitation of this study is that the experimental design was sequential, with light optimization conducted first and MeJA application tested only under the optimal spectrum. Consequently, the results do not represent a full factorial analysis, and conclusions regarding synergistic interactions between light spectra and MeJA are limited. Future studies should adopt factorial designs to more comprehensively elucidate these interactive effects.

4. Conclusions

This study highlights the role of light quality and methyl jasmonate (MeJA) as abiotic stress factors that regulate growth and secondary metabolism in peppermint. The balanced RGB (1:1:1) spectrum created a favorable stress environment, enhancing photosynthesis, chlorophyll content, and biomass accumulation. MeJA acted as a chemical stress signal, stimulating physiological processes such as photosynthetic rate, transpiration, and stomatal conductance, while upregulating defense pathways that increased phenolic content and antioxidant activity. Importantly, the effects were concentration-dependent: moderate levels of MeJA (1.5–2.0 mM) induced beneficial stress responses, whereas higher concentrations (2.5 mM) increased the risk of oxidative stress and reduced the efficiency of secondary metabolite synthesis. Together, these findings demonstrate that the strategic application of light spectrum stress and chemical elicitation can be harnessed to optimize peppermint growth, resilience, and phytochemical quality in controlled environment systems. Future research should investigate molecular mechanisms, broader light and MeJA conditions, as well as long-term metabolomic responses to provide a more comprehensive understanding and validate the practical implications for peppermint cultivation.

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/horticulturae11101243/s1. Figure S1: The experiment was conducted under five different light spectrum ratios; Table S1: Effects of MeJA concentrations on physiological responses of peppermint; Table S2: The quantities of secondary metabolites and antioxidant capacity of peppermint under different concentrations of MeJA.

Author Contributions

Conceptualization, P.C. (Preuk Chutimanukul) and P.C. (Panita Chutimanukul); methodology, P.C. (Preuk Chutimanukul), P.C. (Panita Chutimanukul) and T.D.; validation, P.C. (Preuk Chutimanukul), P.C. (Panita Chutimanukul), O.T. and T.D.; formal analysis, P.C. (Preuk Chutimanukul), T.D. and T.L.; investigation, P.C. (Preuk Chutimanukul) and T.D.; resources, P.C. (Preuk Chutimanukul) and T.D.; data curation, P.C. (Preuk Chutimanukul), O.T., H.E. and P.C. (Panita Chutimanukul); writing—original draft preparation, T.D., P.C. (Preuk Chutimanukul) and S.S.; writing—review and editing, P.C. (Preuk Chutimanukul) and S.S.; supervision, P.C. (Preuk Chutimanukul); project administration, P.C. (Preuk Chutimanukul); funding acquisition, P.C. (Preuk Chutimanukul). All authors have read and agreed to the published version of the manuscript.

Funding

The authors gratefully acknowledge the financial support provided by the Faculty of Science and Technology, Thammasat University, Contract No. SciGR10/2568. This study was supported by the National Center for Genetic Engineering and Biotechnology (BIOTEC), Thailand, grant number P2550484 (basic research fund: fiscal year 2026 with contract No. 4826938).

Data Availability Statement

The original contributions and data presented in this research are included in the article; further inquiries can be directed to the corresponding authors.

Acknowledgments

The authors would like to thank the Faculty of Science and Technology, Thammasat University, for providing technical support and the instruments.

Conflicts of Interest

The authors declare no conflicts of interest.

References

  1. Szymczycha-Madeja, A.; Welna, M.; Zyrnicki, W. Multi-element analysis, bioavailability and fractionation of herbal tea products. J. Braz. Chem. Soc. 2013, 24, 777–787. [Google Scholar] [CrossRef]
  2. Grigoleit, H.-G.; Grigoleit, P. Pharmacology and preclinical pharmacokinetics of peppermint oil. Phytomedicine 2005, 12, 612–616. [Google Scholar] [CrossRef]
  3. Pytlakowska, K.; Kita, A.; Janoska, P.; Połowniak, M.; Kozik, V. Multi-element analysis of mineral and trace elements in medicinal herbs and their infusions. Food Chem. 2012, 135, 494–501. [Google Scholar] [CrossRef]
  4. Canter, P.H.; Thomas, H.; Ernst, E. Bringing medicinal plants into cultivation: Opportunities and challenges for biotechnology. Trends Biotechnol. 2005, 23, 180–185. [Google Scholar] [CrossRef]
  5. Kala, C.P. Problems and prospects in the conservation and development of the Himalayan medicinal plants sector. Int. J. Sustain. Dev. 2006, 9, 370–389. [Google Scholar] [CrossRef]
  6. Dsouza, A.; Dixon, M.; Shukla, M.; Graham, T. Harnessing controlled-environment systems for enhanced production of medicinal plants. J. Exp. Bot. 2025, 76, 76–93. [Google Scholar] [CrossRef]
  7. Kozai, T. Resource use efficiency of closed plant production system with artificial light: Concept, estimation and application to plant factory. Proc. Jpn. Academy. Ser. B Phys. Biol. Sci. 2013, 89, 447–461. [Google Scholar] [CrossRef]
  8. Kozai, T.; Kubota, C.; Chun, C.; Afreen, F.; Ohyama, K. Necessity and Concept of the Closed Transplant Production System; Springer: Dordrecht, The Netherlands, 2000. [Google Scholar]
  9. Kozai, T. Propagation, grafting and transplant production in closed systems with artificial lighting for commercialization in Japan. Propag. Ornam. Plants 2007, 7, 145–149. [Google Scholar]
  10. van Grondelle, R.; Boeker, E. Limits on natural photosynthesis. J. Phys. Chem. B 2017, 121, 7229–7234. [Google Scholar] [CrossRef]
  11. Kume, A. Importance of the green color, absorption gradient, and spectral absorption of chloroplasts for the radiative energy balance of leaves. J. Plant Res. 2017, 130, 501–514. [Google Scholar] [CrossRef]
  12. Liu, J.; Van Iersel, M.W. Photosynthetic physiology of blue, green, and red light: Light intensity effects and underlying mechanisms. Front. Plant Sci. 2021, 12, 619987. [Google Scholar] [CrossRef]
  13. González-Aguilar, G.; Tiznado-Hernandez, M.; Zavaleta-Gatica, R.; Martınez-Téllez, M. Methyl jasmonate treatments reduce chilling injury and activate the defense response of guava fruits. Biochem. Biophys. Res. Commun. 2004, 313, 694–701. [Google Scholar] [CrossRef]
  14. Loreti, E.; Povero, G.; Novi, G.; Solfanelli, C.; Alpi, A.; Perata, P. Gibberellins, jasmonate and abscisic acid modulate the sucrose-induced expression of anthocyanin biosynthetic genes in Arabidopsis. New Phytol. 2008, 179, 1004–1016. [Google Scholar] [CrossRef]
  15. Shinohara, Y.; Suzuki, Y. Quality improvement of hydroponically grown leaf vegetables. In Proceedings of the Symposium on High Technology in Protected Cultivation 230, Hamamatsu, Japan, 12–15 May 1988; pp. 279–286. [Google Scholar]
  16. Chutimanukul, P.; Wanichananan, P.; Janta, S.; Toojinda, T.; Darwell, C.T.; Mosaleeyanon, K. The influence of different light spectra on physiological responses, antioxidant capacity and chemical compositions in two holy basil cultivars. Sci. Rep. 2022, 12, 588. [Google Scholar] [CrossRef]
  17. Chutimanukul, P.; Jindamol, H.; Thongtip, A.; Korinsak, S.; Romyanon, K.; Toojinda, T.; Darwell, C.T.; Wanichananan, P.; Panya, A.; Kaewsri, W.; et al. Physiological responses and variation in secondary metabolite content among Thai holy basil cultivars (Ocimum tenuiflorum L.) grown under controlled environmental conditions in a plant factory. Front. Plant Sci. 2022, 13, 1008917. [Google Scholar] [CrossRef]
  18. Heo, J.; Lee, C.; Chakrabarty, D.; Paek, K. Growth responses of marigold and salvia bedding plants as affected by monochromic or mixture radiation provided by a light-emitting diode (LED). Plant Growth Regul. 2002, 38, 225–230. [Google Scholar] [CrossRef]
  19. Johkan, M.; Shoji, K.; Goto, F.; Hashida, S.-n.; Yoshihara, T. Blue Light-emitting Diode Light Irradiation of Seedlings Improves Seedling Quality and Growth after Transplanting in Red Leaf Lettuce. HortScience 2010, 45, 1809–1814. [Google Scholar] [CrossRef]
  20. Wu, M.-C.; Hou, C.-Y.; Jiang, C.-M.; Wang, Y.-T.; Wang, C.-Y.; Chen, H.-H.; Chang, H.-M. A novel approach of LED light radiation improves the antioxidant activity of pea seedlings. Food Chem. 2007, 101, 1753–1758. [Google Scholar] [CrossRef]
  21. Behringer, F.J.; Davies, P.J. Indole-3-acetic acid levels after phytochrome-mediated changes in the stem elongation rate of dark- and light-grown Pisum seedlings. Planta 1992, 188, 85–92. [Google Scholar] [CrossRef]
  22. Brown, C.S.; Schuerger, A.C.; Sager, J.C. Growth and photomorphogenesis of pepper plants under red light-emitting diodes with supplemental blue or far-red lighting. J. Am. Soc. Hortic. Sci. 1995, 120, 808–813. [Google Scholar] [CrossRef]
  23. Tabbert, J.; Schulz, H.; Krähmer, A. Investigation of LED Light Qualities for Peppermint (Mentha x Piperita L.) Cultivation Focusing on Plant Quality and Consumer Safety Aspects. Front. Food Sci. Technol. 2022, 2, 852155. [Google Scholar] [CrossRef]
  24. Dou, H.; Niu, G.; Gu, M. Photosynthesis, morphology, yield, and phytochemical accumulation in basil plants influenced by substituting green light for partial red and/or blue light. HortScience 2019, 54, 1769–1776. [Google Scholar] [CrossRef]
  25. Kim, H.-H.; Goins, G.; Wheeler, R.; Sager, J. Green-light Supplementation for Enhanced Lettuce Growth under Red- and Blue-light-emitting Diodes. HortScience 2004, 39, 1617–1622. [Google Scholar] [CrossRef]
  26. Wang, J.; Lu, W.; Tong, Y.; Yang, Q. Leaf Morphology, Photosynthetic Performance, Chlorophyll Fluorescence, Stomatal Development of Lettuce (Lactuca sativa L.) Exposed to Different Ratios of Red Light to Blue Light. Front. Plant Sci. 2016, 7, 250. [Google Scholar] [CrossRef]
  27. Trouwborst, G.; Hogewoning, S.W.; van Kooten, O.; Harbinson, J.; van Ieperen, W. Plasticity of photosynthesis after the ‘red light syndrome’ in cucumber. Environ. Exp. Bot. 2016, 121, 75–82. [Google Scholar] [CrossRef]
  28. Taiz, L.; Zeiger, E.; Møller, I.M.; Murphy, A.S. Plant Physiology and Development; Sinauer Associates, Inc Publishers: Sunderland, MA, USA, 2015. [Google Scholar]
  29. Franklin, K.A.; Whitelam, G.C. Light-quality regulation of freezing tolerance in Arabidopsis thaliana. Nat. Genet. 2007, 39, 1410–1413. [Google Scholar] [CrossRef]
  30. Hogewoning, S.W.; Trouwborst, G.; Maljaars, H.; Poorter, H.; van Ieperen, W.; Harbinson, J. Blue light dose–responses of leaf photosynthesis, morphology, and chemical composition of Cucumis sativus grown under different combinations of red and blue light. J. Exp. Bot. 2010, 61, 3107–3117. [Google Scholar] [CrossRef]
  31. Gutiérrez-Boem, F.H.; Thomas, G.W. Phosphorus nutrition affects wheat response to water deficit. Agron. J. 1998, 90, 166–171. [Google Scholar] [CrossRef]
  32. Terashima, I.; Fujita, T.; Inoue, T.; Chow, W.S.; Oguchi, R. Green light drives leaf photosynthesis more efficiently than red light in strong white light: Revisiting the enigmatic question of why leaves are green. Plant Cell Physiol. 2009, 50, 684–697. [Google Scholar] [CrossRef]
  33. Smith, H.L.; McAusland, L.; Murchie, E.H. Don’t ignore the green light: Exploring diverse roles in plant processes. J. Exp. Bot. 2017, 68, 2099–2110. [Google Scholar] [CrossRef]
  34. Schilmiller, A.L.; Koo, A.J.; Howe, G.A. Functional diversification of acyl-coenzyme A oxidases in jasmonic acid biosynthesis and action. Plant Physiol. 2007, 143, 812–824. [Google Scholar] [CrossRef]
  35. Sembdner, G.; Parthier, B. The biochemistry and the physiological and molecular actions of jasmonates. Annu. Rev. Plant Biol. 1993, 44, 569–589. [Google Scholar] [CrossRef]
  36. Wasternack, C.; Hause, B. Jasmonates: Biosynthesis, perception, signal transduction and action in plant stress response, growth and development. An update to the 2007 review in Annals of Botany. Ann. Bot. 2013, 111, 1021–1058. [Google Scholar] [CrossRef]
  37. Ghasemzadeh, A.; Jaafar, H.Z.; Rahmat, A.; Wahab, P.E.M.; Halim, M.R.A. Effect of different light intensities on total phenolics and flavonoids synthesis and anti-oxidant activities in young ginger varieties (Zingiber officinale Roscoe). Int. J. Mol. Sci. 2010, 11, 3885–3897. [Google Scholar] [CrossRef]
  38. Zhang, H.; Hedhili, S.; Montiel, G.; Zhang, Y.; Chatel, G.; Pré, M.; Gantet, P.; Memelink, J. The basic helix-loop-helix transcription factor CrMYC2 controls the jasmonate-responsive expression of the ORCA genes that regulate alkaloid biosynthesis in Catharanthus roseus. Plant J. 2011, 67, 61–71. [Google Scholar] [CrossRef]
  39. Wu, J.; Chen, Y.; Xu, Y.; An, Y.; Hu, Z.; Xiong, A.; Wang, G. Effects of jasmonic acid on stress response and quality formation in vegetable crops and their underlying molecular mechanisms. Plants 2024, 13, 1557. [Google Scholar] [CrossRef]
  40. Ali, M.B.; Singh, N.; Shohael, A.M.; Hahn, E.J.; Paek, K.-Y. Phenolics metabolism and lignin synthesis in root suspension cultures of Panax ginseng in response to copper stress. Plant Sci. 2006, 171, 147–154. [Google Scholar] [CrossRef]
  41. Song, Q.; Gong, W.; Yu, X.; Ji, K.; Jiang, Y.; Chang, Y.; Yuan, D. Transcriptome and Anatomical Comparisons Reveal the Effects of Methyl Jasmonate on the Seed Development of Camellia oleifera. J. Agric. Food Chem. 2023, 71, 6747–6762. [Google Scholar] [CrossRef]
  42. Yin, Y.; Yang, T.; Li, S.; Li, X.; Wang, W.; Fan, S. Transcriptomic analysis reveals that methyl jasmonate confers salt tolerance in alfalfa by regulating antioxidant activity and ion homeostasis. Front. Plant Sci. 2023, 14, 1258498. [Google Scholar] [CrossRef]
  43. Zaid, A.; Mohammad, F. Methyl jasmonate and nitrogen interact to alleviate cadmium stress in Mentha arvensis by regulating physio-biochemical damages and ROS detoxification. J. Plant Growth Regul. 2018, 37, 1331–1348. [Google Scholar] [CrossRef]
  44. Li, C.; Wang, P.; Menzies, N.W.; Lombi, E.; Kopittke, P.M. Effects of methyl jasmonate on plant growth and leaf properties. J. Plant Nutr. Soil Sci. 2018, 181, 409–418. [Google Scholar] [CrossRef]
  45. Kim, H.-J.; Fonseca, J.M.; Choi, J.-H.; Kubota, C. Effect of Methyl Jasmonate on Phenolic Compounds and Carotenoids of Romaine Lettuce (Lactuca sativa L.). J. Agric. Food Chem. 2007, 55, 10366–10372. [Google Scholar] [CrossRef]
  46. Sirhindi, G.; Mushtaq, R.; Gill, S.S.; Sharma, P.; Abd_Allah, E.F.; Ahmad, P. Jasmonic acid and methyl jasmonate modulate growth, photosynthetic activity and expression of photosystem II subunit genes in Brassica oleracea L. Sci. Rep. 2020, 10, 9322. [Google Scholar] [CrossRef]
  47. Lawson, T.; Blatt, M.R. Stomatal size, speed, and responsiveness impact on photosynthesis and water use efficiency. Plant Physiol. 2014, 164, 1556–1570. [Google Scholar] [CrossRef]
  48. Jiang, Y.; Ye, J.; Niinemets, Ü. Dose-dependent methyl jasmonate effects on photosynthetic traits and volatile emissions: Biphasic kinetics and stomatal regulation. Plant Signal. Behav. 2021, 16, 1917169. [Google Scholar] [CrossRef]
  49. Enteshari, S.; Jafari, T. The effects of methyl jasmonate and salinity on germination and seedling growth in Ocimum basilicum L. Iran. J. Plant Physiol. 2013, 3, 749–765. [Google Scholar]
  50. Gundlach, H.; Müller, M.J.; Kutchan, T.M.; Zenk, M.H. Jasmonic acid is a signal transducer in elicitor-induced plant cell cultures. Proc. Natl. Acad. Sci. USA 1992, 89, 2389–2393. [Google Scholar] [CrossRef]
  51. Ali, M.B.; Hahn, E.-J.; Paek, K.-Y. Methyl jasmonate and salicylic acid induced oxidative stress and accumulation of phenolics in Panax ginseng bioreactor root suspension cultures. Molecules 2007, 12, 607–621. [Google Scholar] [CrossRef]
  52. Creelman, R.A.; Mullet, J.E. Biosynthesis and action of jasmonates in plants. Annu. Rev. Plant Biol. 1997, 48, 355–381. [Google Scholar] [CrossRef]
  53. Wang, K.; Jin, P.; Cao, S.; Shang, H.; Yang, Z.; Zheng, Y. Methyl jasmonate reduces decay and enhances antioxidant capacity in Chinese bayberries. J. Agric. Food Chem. 2009, 57, 5809–5815. [Google Scholar] [CrossRef]
  54. Raman, V.; Ravi, S. Effect of salicylic acid and methyl jasmonate on antioxidant systems of Haematococcus pluvialis. Acta Physiol. Plant. 2011, 33, 1043–1049. [Google Scholar] [CrossRef]
  55. Sharma, A.; Shahzad, B.; Rehman, A.; Bhardwaj, R.; Landi, M.; Zheng, B. Response of phenylpropanoid pathway and the role of polyphenols in plants under abiotic stress. Molecules 2019, 24, 2452. [Google Scholar] [CrossRef] [PubMed]
  56. Farooq, M.A.; Gill, R.A.; Islam, F.; Ali, B.; Liu, H.; Xu, J.; He, S.; Zhou, W. Methyl jasmonate regulates antioxidant defense and suppresses arsenic uptake in Brassica napus L. Front. Plant Sci. 2016, 7, 468. [Google Scholar]
  57. Kandoudi, W.; Tavaszi-Sárosi, S.; Németh-Zámboriné, E. Inducing the production of secondary metabolites by foliar application of methyl jasmonate in peppermint. Plants 2023, 12, 2339. [Google Scholar] [CrossRef]
  58. Afkar, S. Response of peppermint to methyl jasmonate application. Iran. J. Plant Physiol. 2015, 6, 1573–1578. [Google Scholar]
  59. Abdi, G.; Shokrpour, M.; Karami, L.; Salami, S.A. Prolonged Water Deficit Stress and Methyl Jasmonate-Mediated Changes in Metabolite Profile, Flavonoid Concentrations and Antioxidant Activity in Peppermint (Mentha × piperita L.). Not. Bot. Horti Agrobot. Cluj-Napoca 2018, 47, 70. [Google Scholar] [CrossRef]
  60. Wang, S.Y.; Bowman, L.; Ding, M. Methyl jasmonate enhances antioxidant activity and flavonoid content in blackberries (Rubus sp.) and promotes antiproliferation of human cancer cells. Food Chem. 2008, 107, 1261–1269. [Google Scholar] [CrossRef]
  61. Talebi, M.; Moghaddam, M.; Pirbalouti, A.G. Methyl jasmonate effects on volatile oil compounds and antioxidant activity of leaf extract of two basil cultivars under salinity stress. Acta Physiol. Plant. 2018, 40, 34. [Google Scholar] [CrossRef]
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Figure 1. Light spectrum ratios (red, blue, and green) applied in the peppermint cultivation experiment (L1–L5).
Figure 1. Light spectrum ratios (red, blue, and green) applied in the peppermint cultivation experiment (L1–L5).
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Figure 2. Correlation plot of peppermint growth and biomass traits under five light spectrum treatments.
Figure 2. Correlation plot of peppermint growth and biomass traits under five light spectrum treatments.
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Figure 3. Growth responses of peppermint under different methyl jasmonate (MeJA) concentrations: 0 mM, 0.5 mM, 1.0 mM, 1.5 mM, 2.0 mM, and 2.5 mM.
Figure 3. Growth responses of peppermint under different methyl jasmonate (MeJA) concentrations: 0 mM, 0.5 mM, 1.0 mM, 1.5 mM, 2.0 mM, and 2.5 mM.
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Figure 4. Correlation plot of peppermint growth and physiological traits under different concentrations of methyl jasmonate (MeJA).
Figure 4. Correlation plot of peppermint growth and physiological traits under different concentrations of methyl jasmonate (MeJA).
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Figure 5. Effects of MeJA concentrations on physiological responses of peppermint, including photosynthetic rate (A), transpiration rate (B), stomatal conductance (C), and intercellular CO2 concentration (D). Values are means with standard deviations (n = 5).
Figure 5. Effects of MeJA concentrations on physiological responses of peppermint, including photosynthetic rate (A), transpiration rate (B), stomatal conductance (C), and intercellular CO2 concentration (D). Values are means with standard deviations (n = 5).
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Figure 6. The quantities of secondary metabolites and antioxidant capacity of peppermint under different concentrations of methyl jasmonate (MeJA), including total phenolic (A), flavonoid (B), DPPH scavenging activity (C), and anthocyanin (D). Values are means with standard deviations (n = 5).
Figure 6. The quantities of secondary metabolites and antioxidant capacity of peppermint under different concentrations of methyl jasmonate (MeJA), including total phenolic (A), flavonoid (B), DPPH scavenging activity (C), and anthocyanin (D). Values are means with standard deviations (n = 5).
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Table 1. Morphological traits and chlorophyll content of peppermint in response to different light spectrum treatments.
Table 1. Morphological traits and chlorophyll content of peppermint in response to different light spectrum treatments.
Light SpectrumPlant Height
(cm)		Canopy Width (cm)Leaf Area
(cm2)		Number of Leaf PairsSPAD Unit
1R:1G:1B35.99 ± 0.77 a21.24 ± 1.54 a16.18 ± 0.60 a8.40 ± 0.3229.64 ± 2.34 a
2R:1G:2B33.96 ± 0.51 b13.20 ± 0.62 d12.88 ± 0.43 b8.20 ± 0.8425.26 ± 0.75 bc
1R:1B30.34 ± 0.30 d15.58 ± 0.77 c11.97 ± 0.69 c8.40 ± 0.5524.03 ± 1.51 c
1R:3B32.96 ± 1.00 c17.10 ± 0.91 b12.14 ± 0.51 c8.24 ± 0.6525.69 ± 2.79 bc
3R:1B34.07 ± 0.65 b12.50 ± 1.09 d12.37 ± 0.24 bc7.96 ± 0.5226.90 ± 1.47 b
F-test******ns**
C.V. (%)5.8120.4912.476.809.73
The data are presented as mean ± standard deviation (SD) (n = 5). Distinct letters within the same column indicate significant differences between treatments, as determined by Duncan’s multiple range test (DMRT) at p < 0.05. ** There were significant differences at p < 0.01 and ns = not significant.
Table 2. Biomass accumulation of peppermint in response to different light spectrum treatments.
Table 2. Biomass accumulation of peppermint in response to different light spectrum treatments.
Light SpectrumFresh Weight of Leaves (g/plant)Dry Weight of Leaves (g/plant)Fresh Weight of Stem (g/plant)Dry Weight of
Stem (g/plant)
1R:1G:1B11.21 ± 0.59 a1.05 ± 0.18 a11.60 ± 0.29 a0.86 ± 0.06 a
2R:1G:2B7.99 ± 0.74 d0.71 ± 0.06 bc7.01 ± 0.70 c0.41 ± 0.04 d
1R:1B9.54 ± 0.27 c0.69 ± 0.12 bc6.74 ± 0.45 c0.57 ± 0.07 b
1R:3B10.50 ± 0.50 b0.87 ± 0.13 b9.50 ± 0.32 b0.49 ± 0.05 c
3R:1B7.29 ± 0.43 d0.56 ± 0.14 c6.69 ± 0.35 c0.55 ± 0.03 bc
F-test********
C.V. (%)16.6626.5823.9528.30
The data are presented as mean ± standard deviation (SD) (n = 5). Distinct letters within the same column indicate significant differences between treatments, as determined by Duncan’s multiple range test (DMRT) at p < 0.05. ** There were significant differences at p < 0.01.
Table 3. Growth responses of peppermint under different MeJA concentrations.
Table 3. Growth responses of peppermint under different MeJA concentrations.
Concentration of MeJA
(mM)		Plant Height
(cm)		Canopy Width (cm)Leaf Area
(cm2)		Number of Leaf PairsSPAD Unit
028.65 ± 2.17 c26.17 ± 3.00 c20.95 ± 0.29 d6.88 ± 0.18 b32.61 ± 0.92
0.532.21 ± 2.35 b29.61 ± 1.07 b25.35 ± 0.35 b7.04 ± 0.48 b32.52 ± 0.65
1.031.55 ± 2.02 b29.01 ± 1.65 b22.97 ± 1.75 c6.96 ± 0.30 b33.35 ± 3.17
1.532.21 ± 2.23 b35.13 ± 0.59 a23.69 ± 0.77 c7.36 ± 0.36 b33.59 ± 2.67
2.036.16 ± 1.20 a34.20 ± 0.46 a26.95 ± 0.99 a7.44 ± 0.22 b31.89 ± 0.78
2.533.20 ± 0.84 b30.01 ± 0.39 b26.48 ± 0.45 ab8.16 ± 0.71 a34.10 ± 2.04
F-test********ns
C.V. (%)8.6310.959.197.805.79
The data are presented as mean ± standard deviation (SD) (n = 5). Distinct letters within the same column indicate significant differences between treatments, as determined by Duncan’s multiple range test (DMRT) at p < 0.05. ** There were significant differences at p < 0.01 and ns = not significant.
Table 4. Biomass responses of peppermint under different MeJA concentrations.
Table 4. Biomass responses of peppermint under different MeJA concentrations.
Concentration of MeJA
(mM)		Fresh Weight of Leaves (g/plant)Dry Weight of Leaves (g/plant)Fresh Weight of Stem (g/plant)Dry Weight of
Stem (g/plant)
019.58 ± 0.79 b1.77 ± 0.34 c18.08 ± 0.68 c1.22 ± 0.18 bc
0.516.67 ± 1.16 c1.77 ± 0.20 c15.67 ± 0.23 d1.05 ± 0.05 c
1.018.00 ± 0.73 c2.03 ± 0.25 bc15.68 ± 0.59 d1.18 ± 0.15 bc
1.520.06 ± 0.77 b2.31 ± 0.28 ab18.06 ± 0.62 c1.31 ± 0.09 b
2.020.70 ± 1.90 b2.20 ± 0.12 b19.44 ± 1.36 b1.36 ± 0.19 b
2.524.82 ± 0.80 a2.42 ± 0.24 a22.28 ± 0.35 a1.70 ± 0.19 a
F-test********
C.V. (%)13.7016.0312.9918.74
The data are presented as mean ± standard deviation (SD) (n = 5). Distinct letters within the same column indicate significant differences between treatments, as determined by Duncan’s multiple range test (DMRT) at p < 0.05. ** There were significant differences at p < 0.01.
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MDPI and ACS Style

Dangsamer, T.; Chutimanukul, P.; Sukdee, S.; Liamjinda, T.; Thepsilvisut, O.; Ehara, H.; Chutimanukul, P. Physiological and Biochemical Responses of Mentha spp. to Light Spectrum and Methyl Jasmonate in a Controlled Plant Factory Environment. Horticulturae 2025, 11, 1243. https://doi.org/10.3390/horticulturae11101243

AMA Style

Dangsamer T, Chutimanukul P, Sukdee S, Liamjinda T, Thepsilvisut O, Ehara H, Chutimanukul P. Physiological and Biochemical Responses of Mentha spp. to Light Spectrum and Methyl Jasmonate in a Controlled Plant Factory Environment. Horticulturae. 2025; 11(10):1243. https://doi.org/10.3390/horticulturae11101243

Chicago/Turabian Style

Dangsamer, Thanyaluk, Panita Chutimanukul, Siripong Sukdee, Theeraphat Liamjinda, Ornprapa Thepsilvisut, Hiroshi Ehara, and Preuk Chutimanukul. 2025. "Physiological and Biochemical Responses of Mentha spp. to Light Spectrum and Methyl Jasmonate in a Controlled Plant Factory Environment" Horticulturae 11, no. 10: 1243. https://doi.org/10.3390/horticulturae11101243

APA Style

Dangsamer, T., Chutimanukul, P., Sukdee, S., Liamjinda, T., Thepsilvisut, O., Ehara, H., & Chutimanukul, P. (2025). Physiological and Biochemical Responses of Mentha spp. to Light Spectrum and Methyl Jasmonate in a Controlled Plant Factory Environment. Horticulturae, 11(10), 1243. https://doi.org/10.3390/horticulturae11101243

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