Nanosilicon application changes the morphological attributes and essential oil compositions of hemp (Cannabis sativa L.) under water deficit stress

Drought frequency and intensity have increased globally due to climate change1. Prolonged periods of low rainfall or drought have a huge impact on agriculture and food production and, security2. Reduced crop yields, livestock losses, and dwindling water for irrigation are just some of the disastrous effects of drought on agricultural productivity3,4. Water deficit stress triggers distinct physiological, molecular and biochemical responses in medicinal and aromatic plants (MAPs) and affected their bioactive compounds production5,6. Reduced plant growth, biomass accumulation, and overall yield in MAPs can result from water deficit stress. This is often linked to decreased photosynthetic activity and nutrient uptake due to stomatal closure and decreased turgor pressure7. Research has shown that production and quality of MAPs active compounds including flavonoids, alkaloids and essential oils can be affected by water deficit stress as a defense mechanism8. Studies have shown that specific transcription factors and regulatory genes play a mediating role in the response of MAPs to drought stress and the regulation of bioactive compound production9,10.

A focus on adaptation and resilience-building approaches is necessary in agricultural practices and policies to address the challenges arisen by droughts. This involves encouraging the use of drought-tolerant crop varieties, putting water-efficient irrigation techniques into practice, implementing agroforestry and soil conservation practices, and application of nano-stimulants as mitigating agents of biotic and abiotic stress11,12,13. In the twenty-first century, nanotechnology can completely transform the agricultural industry14. Many countries that are strongly dependent on agriculture are previously using nanotechnology to improve food processing, increase crop productivity and food security15. In agriculture, nanomaterials are needed at many stages from storing water to delivering fertilizers and nutrients in a precise way16,17. Silicon nanoparticles have shown promise in supporting healthy plant growth especially crop productivity during biotic or abiotic stressors18. It has been reported that applying silicon nanoparticles is a proper substitute for silicon in traditional mineral fertilizers19. Moreover, it has been proposed that silica oxide nanoparticles can thicken cell walls and therefore, prevent the penetration of bacteria, and boost disease resistance20. Because of its distinct size in relation to bulk silicon, nanosilicon has exceptional physicochemical properties, including a large surface area, high surface reactivity, and solubility21. Previous investigations have proven that the application of nanosilicon significantly increased agromorphological traits, as well as improved the photosynthetic rate and stomatal conductivity under stress conditions thereby moderating the ruinous effects of abiotic and biotic stress in plants22,23. Some previous publications have investigated the effect of nanosilicon on the essential oil of several medicinal plants including Coriandrum Sativum L.24, Mentha piperita25, Cymbopogon flexuosus26, and Artemisia annua27, wherein reflected the positive effects of nanosilicon in both normal and stress conditions. For example, a study highlighted the hemp essential oil content under drought stress, which showed that the moderate drought stress increased its content in hemp, while the severe or prolonged drought reduced its overall yield28.

Hemp (Cannabis sativa L.) is a highly valuable crop due to its rich bioactive compounds (cannabinoids, terpenes, and flavonoids) that support medicinal and therapeutic uses, including anti-inflammatory and antibacterial applications29. Its growing economic significance spans pharmaceuticals, cosmetics, and food industries, responding to increasing demand for natural products30. Hemp donates a diverse array of biologically bioactive compounds that are synthesized in various components of the plant, making it one of the most promising crops31. Monoterpenoids and, to a lesser extent, sesquiterpenes form the main constituents of hemp essential oil32. Some manufacturers in the United States are creating new products using essential oils or cannabinoids extracted from hemp33. Hemp essential oil has been employed as a main ingredient in commercial insect repellent and biopesticide products, and also possess pharmacological properties34,35. A number commercial products have been developed from hemp essential oil such as skin creams and lotions, perfume and drugs. Due to the recent surge in the price of hemp essential oil, specific cultivars, like Finola, are now used in the commercial production33. Terpenes found in hemp essential oil play a role in the distinct aroma of various cannabis strains. There is a recognized association between the concentration of terpenes and certain cannabinoids, leading to the belief that terpenes have played a significant role in the cultivation and selection of medical, recreational, and CBD-dominant cannabis varieties36. The biological activity of hemp essential oil has been demonstrated against multiple fungal and Bactria species and cancer cell lines37. Various studies have conducted related to hemp essential oil, including factors influencing its performance and quality38, effects of varieties and growth stages on its yield and composition39, its antibacterial properties40, and its potential as an effective insecticidal tool for organic farming. The proper results were obtained by hemp essential oil as a natural insecticide against mosquitoes, houseflies, and aphids41. Hemp essential oil has potent allelopathic effects on invasive weed germination and seedling growth in the agricultural field42. Curiously, EOs have been shown to be effective against dermatophyte species, which suggests that they may help prevent skin conditions43. It is also known as as a flavoring agent for beverages in the food industry. Monoterpenes and sesquiterpenes are the main group of this plant’s essential oil44. Nearly every compound found in the EO has a distinct scent, which can affect consumer preferences. About hemp, Plants with a higher monoterpene content in the essential oil are preferred45. Hemp produces more cannabinoids and terpenes in stress condition, which serve as natural defenses against herbivores and microbes46. In drought conditions, it generates osmo-protectants and raises the level of cannabinoid that help maintain cell structure and act as antioxidants47. However, prolonged stress can deplete the plant’s energy, leading to reduced growth and lower essential oil yields, as the plant energy is diverted to maintain cell health and produce stress-related metabolites48. Thus, while stress boosts cannabinoid and terpene production, it ultimately hampers overall biomass and essential oil output49.So far, different reports have focused on genetic50, phytochemical51, and biological52 aspects of hemp plant, but no study has been performed aiming clear the interaction effect of nanosilicon and drought stress on morphological attributes and essential oil content and compositions of hemp. It has also been noted that each of the main compounds in hemp essential oil exhibits distinct pharmacological effects53. Therefore, alterations in the essential oil composition may significantly influence the medicinal properties of the plant. This study specifically addressed the gap in understanding how hemp can be cultivated under challenging conditions, such as water deficit stress, with the application of nanosilicon, providing valuable insights into improving its essential oil compositions.

Experimental design and treatments

This study was accomplished during the growth period of 2022–2023 at the greenhouse of Shahid Beheshti University, Tehran, Iran. The seeds of hemp were prepared from the Abarkoh region in the Yazd province and subsequently transported to the greenhouse and then cultivated in the planting trays. The plants experienced daily temperatures ranging from 18 to 28°C, with a relative humidity of approximately 69% and light intensity of 55,000 lx. A photoperiod of 16 h was maintained for the vegetative growth stage, which then transitioned to 12 h during the reproductive growth stage. Three weeks after germination, each individual seedling was carefully transferred into its own individual pot. The physiochemical properties of the mixture used in the pots are presented in Table 1. Drought stress was implemented by assessing the field capacity and its corresponding percentages. Initially, the pots containing oven-dried soil were weighed, and a random selection of these pots was irrigated until saturated. After 24 h, the pots were weighed again to establish the 100% field capacity. The other stress levels were then defined as percentages of this 100% field capacity. Every two days, the pots were weighed, and irrigation was adjusted based on the determined water deficit. After two weeks, a factorial experiment based on randomized complete design (RCD) was organized. The plants were subjected to four different irrigation regimes, including optimal irrigation (control) at 100% field capacity (FC), mild stress at 80% FC, moderate stress at 60% FC, and severe stress at 40% FC, in combination with three concentrations of nanosilicon (0, 0.5, and 1.5 mM), mixed with 0.01% Tween 20 to reduce the water repellency on the leaves for 40 days. The watering schedule was determined and implemented by weighing each pot and adjusting it to reach its FC. Alongside the irrigation schedule, nanosilicon was sprayed on the plant leaves every ten days. During the experiment, no fertilizers or pesticides were applied, and weed management was done manually. At the end of the trial period, the plant samples were collected in the flowering phase for morphological and essential oil analysis.

Morphological evaluation

The plants were cut from the soil surface in the flowering period, wherein three plant samples from each treatment were assessed to quantify some morphological characteristics including plant height, stem diameter, number of node, number of flowering branch, fresh and dry weights of the shoots (leaf, stem and flower). The dry weight of the shoots was determined after drying the plant in a well-ventilated shaded condition. All the aforementioned traits were measured using a ruler, caliper, and semi-sensitive scale.

Essential oil extraction

The essential oil (EO) of the samples was obtained according to the British Pharmacopoeia (BP) method54. For this purpose, the hydrodistillation was applied for essential oil extraction from 20 g of dried and chopped inflorescences, particularly the floral bracts, using Clevenger-type device for 3 h. The obtained EOs were injected into gas chromatography for analysis.

Gas chromatography analysis and compound identification

The analysis of the EO was carried out utilizing a gas chromatograph (GC) that was connected to a specialized column (DB-5) and a flame ionization detector (FID). The temperatures of the injector and detector were upheld at 250 °C and 300 °C, respectively. Nitrogen was employed as the carrier gas at a flow rate of 1.1 ml/min. The program of oven temperature began at 60 °C and increased at a rate of 5 °C per minute until reaching 250 °C, where it remained isothermal for 10 min.

The GC–MS analysis was conducted utilizing a Thermoquest-Finnigan gas chromatograph featuring a fused silica capillary HP-5MS column with dimensions of 60 m in length, 0.25 mm in inner diameter, and a film thickness of 0.25 µm. The instrument was coupled with a TRACE mass spectrometer sourced from Manchester, UK. Helium was the carrier gas, and the ionization voltage was set at 70 electron volts. The ion source and interface temperatures were maintained at 200 °C and 250 °C, respectively. The mass spectrometer operated within a mass range spanning from 40 to 460 atomic mass units. The temperature program in the oven was consistent with that employed in the GC-FID analysis.

The identification of EO constituents was conducted by determining their retention indices through temperature-programmed analysis with n-alkanes (C6–C24) and comparing them with the oil on a DB-5 column using identical chromatographic conditions. The compounds were identified by comparing their mass spectra with those in an internal reference mass spectra library (Adams and Wiley 7.0) or with verified standards. Confirmation of identification was achieved by comparing retention indices with those of authenticated compounds or references in the literature. Quantification of the compounds was performed by determining relative area percentages from flame ionization detector (FID) signals, without the application of correction factors55.

Statistical analysis

The data analysis was conducted using SAS software version 9.4, which involved performing analysis of variance (ANOVA) and Duncan’s multiple range test to compare means with a confidence level of 95%. Pearson correlation, heat map, and PCA analyses were performed using Origin software. The diagrams were also generated using Origin software.

Agromorphological traits

The analysis of variance (ANOVA) revealed that the drought stress had a statistically significant effect on the all measured agromorphological traits at the 5% probability level, as shown in the Table S1. The statistically significant effect of nanosilicon on the all studied agromorphological traits was also observed, except for flower dry weight. The interaction effect of drought stress and nanosilicon was not significant on the number of flowering branches, while it was significant for the other studied morphological traits.

The measured morphological parameters were significantly affected by soil water capacity, wherein a decrease in the growth parameters of the plant exposed to water deficit conditions was observed (Fig. 1). The results revealed a significant decrease in the plants height under severe drought stress (92.5 cm) compared with the control (41.9 cm). Treatment with nanosilicon increased the plant’s height, with the maximum value observed at 1.5 mM nanosilicon under 100% FC (109 cm). Additionally, under severe drought stress, plants treated with 1.5 mM nanosilicon exhibited a 1.45-fold increase in height compared with the control group. This increase was not significantly different from the plant exposed to 0.5 mM nanosilicon under severe drought stress. The negative effects of drought were also observed in the number of flowering branches, wherein the lowest number (14) was related to 40% FC, without nanosilicon application. The application of 0.5 mM nanosilicon increased its value (18), whereas was not significantly different from the 1.5 mM nanosilicon treatment (17.6). The highest number of flowering branches was observed in the 100% FC and 1.5 mM nanosilicon (29.3), showing a 1.19-fold increase compared with the control treatment (24.6) (100% FC without nanosilicon). In all drought levels, the application of 1.5 mM nanosilicon consistently resulted in maximum number of nodes compared with other treatments. At 100% FC, the number of nodes raised at 1.5 mM nanosilicon (33.3), indicating a significant positive impact of nanosilicon on nodal development under optimal water conditions. The least diameter was observed in the treatment with 0.5 mM nanosilicon under severe water stress (5.43 mm), which represents a 1.49-fold decrease compared with the control (8.13 mm). Conversely, the largest stem diameter was found under 80% FC without nanosilicon (11.5 mm), which was not significantly different with 1.5 mM nanosilicon application under 100% FC.

Under different irrigation regimes without nanosilicon treatment (control), the highest stem fresh weight was observed at 80% FC (29.2 g), while the lowest value was at 40% FC (14.5 g). The application of 0.5 mM nanosilicon at 80% FC led to highest stem fresh weight (39.7 g) compared with the other treatments (Fig. 2-A). Regarding the stem dry weight, the highest stem dry weight (12.8 g) was recorded under 100% FC with 1.5 mM nanosilicon treatment, while the lowest value (2.6 g) was observed under 40% FC and application of 0.5 mM nanosilicon without significant differences with the same irrigation regime and non-nanosilicon treatment (Fig. 2-B).

As expected, under different water regimes the highest (24.3 g) and lowest (12.8 g) leaf fresh weight was observed in 100% FC and at 40% FC, respectively, without nanosilicon application. However, the highest leaf fresh weight among all treatments was related to 1.5 mM nanosilicon and 100% FC with (48.4 g) (Fig. 2-C). The leaf dry weight followed the same trend with its fresh weight. The lowest dry weight (3.1 g) was observed under 40% FC without nanosilicon application. Conversely, the highest leaf dry weight (17.3 g), was recorded under 100% FC and 1.5 mM nanosilicon treatment, representing a 2.1-fold increase compared with the control treatment (Fig. 2-D).

The flower fresh weight was decreased in 40% FC compared with 100% FC without nanosilicon application. In contrast, the use of 0.5 mM nanosilicon at 80% FC significantly increased the flower fresh weight (58.7 g) compared with other treatments. The highest flower dry weight in the in non-nanosilicon application was associated to 60% FC (17 g), while the lowest value was observed in the 40% FC (4 g). The use of 1.5 mM nanosilicon in 80% FC significantly increased the flower dry weight compared with other treatments (20 g) (Fig. 3).

Overall, with the increase of water stress, a considerable decrease in the studied agromorphological values was observed. The lowest values for height, stem diameter, number of nodes and flowering branches, as well as fresh and dry weight of different aerial parts were observed at the severe water stress without nanosilicon treatment. On the other hand, using 1.5 mM nanosilicon led to an increase in the most of agromorphological traits.

Essential oil content and compositions

Significant fluctuations in the EO content were noted across various combined drought levels and nanosilicon treatments, as illustrated in Table 2. Without foliar nanosilicon application, the 80% FC increased the EO content (0.13%) by 62.5% compared with well-watered plants (0.08%). The 80% FC combined with foliar application of 1.5 mM nanosilicon led to highest EO content (0.17%) compared with the other treatments. In contrast, the negative effects of 40% FC stress on EO content were observed, while the application of nanosilicon mitigated the negative effects of 40% FC and enhanced EO content. Under the 40% FC, application of 1.5 mM nanosilicon boosted the EO content by 37.5% compared with the plants non-treated with nanosilicon.

The results of this study showed that about of 30 compounds were identified in the hemp EO, which included 98% of the total compounds. As demonstrated in Table 3, the major components of hemp EO were β-myrcene (ranged from 32.00% to 61.67%), D-limonene (3.94–10.45%), β-ocimene (1.70% to 26.18), caryophyllene (1.54–25.50%), and cannabidiol (0.54–7.74%). Under drought stress without nanosilicon application, the content of β-myrcene was about 57.64%, which was associated to the 60% FC. The application of 0.5 mM nanosilicon under 80% FC led to highest level of β-myrcene (61.67%) among the all treatments. The maximum content of D-limonene was obtained in the 40% FC and 1.5 mM nanosilicon treatment (10.45%), while the highest content of β-ocimen was recorded in 60% FC and 1.5 mM nanosilicon (26.18%). The caryophyllene content was in highest value (25.50%) was obtained in 80% FC without nanosilicon application. Finally, the combined effect of 40% FC and 0.5 mM nanosilicon led to maximum content of cannabidiol (CBD) (7.74%) compared with the other treatments.

Pearson correlation and PCA for agromorphological and biochemical characteristics

The Pearson correlation coefficient between morphological traits and major compounds of hemp essential oil showed that number of node (NN) was positively correlated with β-myrcene in EO (r = 0.58). D-limonene value indicated a negative relationship with stem diameter (r = 0.66). β-myrcene content in the plant EO was negatively correlated with caryophyllene (r = -0.67) and α-humulene (r = -0.82). The Pearson correlation analysis showed that no significant negative relationship between morphological traits was observed (Table S2). The heatmap analysis is presented in the Fig. 4 showcasing the relationship among measured traits and treatments. The highest increase in plant height was recorded in non-drought treatments with or without nano-silicon application. The greatest value of β-myrcene was also observed in the combined 80% FC (mild stress) and 0.5 mM nano-silicon treatment. Figure 5 shows the biplot of PCA analysis for the agromorphological traits and major components in the plant EO under drought stress and nanosilicon application, wherein there traits were placed in the first (PC1) and second components (PC2) indicating 54.04% and 17.52% of the total variance, respectively. This analysis indicated that the combined treatment of 100 FC with 1.5 mM nano-silicon application had the greatest effect on agromorphological traits. Also, the severe stress (40% field capacity) combined with 1.5 mM nanosilicon had the most positive effect on the content of cannabidiol. Resulting from the heat map (Fig. 4), although the mild stress (80% FC) combined with 0.5 mM nano-silicon had the highest effect on the fresh flower weight (FFW) value and β-myrcene content, according to the results of the Pearson correlation analysis (Table S2), a significant positive correlation was not observed between the FFW and the β-myrcene content.

Drought stress induces significant morphological and anatomical changes in plants as adaptive mechanisms to conserve water and optimize growth under limited water availability56. These changes include reducing plant height and shoot growth, decreasing leaf size and area, increasing leaf thickness and trichome density, altering leaf angle and mesophyll cell structure, modification of stomatal size, density and position, and early leaf senescence57. These adaptations aim to reduce water loss, optimize light interception and photosynthesis, and protect against oxidative damage. However, severe or prolonged drought can have detrimental effects on plant growth, productivity, and survival, with the specific changes varying among plant species58. Drought stress significantly reduces plant height and the number of nodes, primarily due to reduced cell expansion59. The results obtained in this experiment showed that drought stress alone caused a decrease in the plant height from 92.5 cm at 100% FC to 41.9 cm at 40% FC. The previous study showed that there was a significant reduction in the height of sorghum plant under moderate drought stress60. Decrease in the number of leaf or nodes has been also observed under drought stress due to the inhibition of shoot growth under water-limited conditions61. Drought stress can impact stem diameter and the number of flowering branches in plants, nevertheless, the effects may vary across species and the severity of drought62. In this experiment, the results showed the same trend of reduction in the number of nodes and stem diameter, wherein a significant decrease in these parameters was observed under severe drought stress compared with the 100% FC. However, it has been reported that stem diameter tends to increase under drought stress, particularly in severe drought conditions, as an adaptive response to provide better structural support and water transport capacity, which is contrary to the results obtained in this study63. According to the results obtained in this research, a decrease in the number of flowering branches was observed in 40% FC, without nanosilicon64. For example, while some annual herbaceous plants marginally increased the number of second-level stem branches to better resistance to severe drought, flower number typically decreased with reduced water availability65. Therefore, although stem diameter may increase as an adaptive mechanism to drought, the number of flowering branches could potentially decrease66. Drought stress tends to significantly reduce the fresh and dry weights of the aerial parts of plants, as shown by previous studies67,68. The results obtained in this experiment indicated this reduction, as a significant reduction in fresh and dry weight of flowers was obtained in 40% FC. This reduction in aerial part biomass is a common response to limited water availability, as plants prioritize resource allocation towards root growth and other adaptive mechanisms to conserve water and survive in the drought condition69,70. However, the specific effects can vary based on factors such as the plant species, severity of drought stress, and potential mitigation strategies employed by plants.

Stimulants, including biostimulants and trace elements, are essential in helping plants thrive under high-stress conditions such as drought, salinity, and extreme temperatures71. These compounds enhance physiological and biochemical processes, allowing plants to sustain growth and productivity even with environmental challenges72. They improve nutrient uptake, stimulate the production of antioxidants, and activate stress-responsive pathways, thereby protecting plants against stress73. Among these stimulants, nanosilicon stands out for its efficacy. Silicon in nanoparticle form significantly boosted plant resilience by enhancing water uptake, strengthening cell walls, and activating stress-related genes74. In some previous studies, the beneficial effects of silicon and nanosilicon on plant growth and performance in normal conditions have been mentioned. It is also reported that these beneficial effects help the plant in stress conditions. Under drought conditions, nanosilicon helps maintain higher photosynthetic rates and reduces oxidative damage, enabling plants to manage limited resources more efficiently75. Treatment with nanosilicon has been shown to improve stem length/height, leaf area index (LAI), and root biomass in plants like wheat, damask rose, and olive trees subjected to drought stress induced by polyethylene glycol (PEG) or water deficit conditions18,76. Additionally, nanosilicon has been found to promote root growth and development under drought conditions, contributing to improved water and nutrient uptake. Consequently, the application of nanosilicon has led to increased total biomass accumulation, yield, and fruit weight in various plant species exposed to moderate to severe drought stress77. These beneficial effects of nanosilicon on plant morphology under drought are attributed to its role in improving water uptake, nutrient availability, photosynthesis, osmotic adjustment, and oxidative stress tolerance78.

Environmental stresses play a crucial role in the production of EO in plants, including hemp79. Our findings showed that the 80% FC condition combined with nanosilicon improved EO content, aligning with prior research on drought stress effects80,81. The enhanced EO content under 80% FC, may be attributed to the increased precursor availability and metabolic shifts in plant82. In line with the present study, drought stress has significantly influenced the EO composition of the hemp plant83. The EO of hemp is responsible for the plant’s distinctive aroma and contributes to its therapeutic effects44. Drought stress can lead to changes in the relative concentrations of different EO compositions in the hemp plant (Table 2). For example, previous study has shown that the levels of specific terpenes like myrcene, limonene, and pinene increased under drought conditions, while others like linalool and terpinolene decreased83. Similar to other aromatic plants like Origanum vulgare and Rosmarinus officinalis, moderate drought stress increased the total concentration of terpenes in hemp plants84. This is likely a defensive response to alert neighboring tissue or plants under dangerous situations such as herbivore attacks or drought stress85,86. Under drought conditions, hemp plants produce more osmoprotectants and antioxidants, which can influence the biosynthesis of terpenes and cannabinoids87. This osmotic stress response, coupled with hormonal changes such as increased levels of abscisic acid (ABA), alters terpene synthesis pathways. Additionally, drought triggers changes in the expression of genes involved in terpene biosynthesis, leading to modified profiles of EOs88,89.

It is important to note that the ratio of these main EO components can vary depending on the intensity of irrigation and the cultivation area. According to the obtained results, drought had negative effects on the percentage and compounds of hemp essential oil, while the application of nanosilicon improved plant condition facing drought and the highest content of essential oil was obtained with the 1.5 mM nanosilicon. The application of nanosilicon decreased the components of Artemisia annua essential oil while increasing the content of some main components of the essential oil like eucalyptol, artemisia ketone, and Camphor27. In this study, it was found that the severe drought stress condition along with the use of nanosilicon had the greatest effect in increasing the content of D-limonene and cannabidiol as one of the important components of plant essential oils, while the highest content of caryophyllene and α-humulene was obtained in conditions without drought stress. Although the biological effects of plant essential oils are usually the result of the synergistic effects of its various compounds, the pharmacological effects of each of the main components of essential oils can also be considered, for example the sedative effects of cannabis products are thought to be linked to β-Myrcene, whereas α-pinene improves learning and memory by inhibiting acetylcholinesterase90. β-caryophyllene and caryophyllene oxide are known to have anti-proliferative and analgesic properties91. Additionally, because hemp terpenes can interact with neurotransmitter receptors and increase blood–brain barrier permeability, they may improve some biological qualities associated with cannabinoids92. In addition to the pharmacological effects mentioned, the allopathic and pesticide effects of hemp essential oil have been proven. The positive effect of nanosilicon application on essential oil yield in lemongrass and other aromatic plants, like coriander and basil, under drought conditions, has been previously investigated24,26,93. This suggests that the use of nanosilicon can help maintain and even enhance the quantity and quality of essential oil in plants exposed to drought stress.

As shown in this study, drought stress, especially severe stress (40% field capacity), led to a significant decrease in the studied agromorphological traits of the hemp plant. Although drought stress reduced the overall essential oil content, the severe drought stress (40% field capacity) combined with nanosilicon application resulted in the highest levels of D-limonene (in the 1.5 mM nanosilicon treatment) and cannabidiol (in the 0.5 mM nanosilicon treatment), as significant components of plant essential oils. In contrast, the maximum levels of caryophyllene and α-humulene were observed under normal conditions (80% field capacity) without nanosilicon application. Resulting from the heat map (Fig. 4), the mild stress (80% FC) combined with 0.5 mM nano-silicon had the highest effect on the fresh flower weight (FFW) value and β-myrcene content. On the other hand, the application of nanosilicon, as a stimulant, showed promising results for improving the growth and development of hemp plants in both normal and drought conditions. The foliar application of nanosilicon helped the hemp plant to cope water deficit stress by modulating various morphological and biochemical responses, wherein an increase in production of essential oil and changing in the major component of essential oil was recorded. The results proposed that the application of 1.5 mM nanosilicon, as a more efficient concentration, improved the drought tolerance in the hemp plants. The use of nanosilicon-based stimulants represents a novel and eco-friendly approach to optimizing the hemp plant performance and productivity, for the both agricultural and pharmaceutical industries. This optimization by using the synergistic effects of essential oil compounds or any of its components alone can lead to more efficient use of plant essential oils as pesticides or medicinal uses.