مجله تحقیقات گیاهان دارویی و معطر ایران
سال چهل و یکم شماره 1 (پیاپی 123، بهار 1404)

Digitalis purpurea L., the most well-known species of the Digitalis genus, is a biennial plant containing cardiac glycosides (0.3 to 0.4%) in its leaves. These glycosides are extracted and used as natural medicines for treating heart diseases, with no chemical substitutes available, making them widely utilized annually. In recent years, using amino acids and growth regulators as alternatives to chemical compounds has gained popularity for enhancing secondary metabolites, improving the quality and quantity of agricultural products, and promoting sustainable agriculture. This study investigates the biochemical and growth responses of D. purpurea to foliar applications of glutamic acid and benzyladenine under greenhouse conditions to evaluate their effects on morphophysiological characteristics, yield improvement, and their potential as environmentally friendly alternatives to chemical fertilizers.

A completely randomized design with three replications was conducted in the research greenhouse of the University of Zanjan to evaluate the effects of foliar applications of benzyladenine (0.5 and 1 mM) and glutamic acid (1 and 2 mM), along with a control treatment (distilled water). Seeds were initially planted in a seedling tray containing cocopeat and peat moss. At the four-leaf stage, three seedlings were transplanted into plastic pots filled with a culture medium of field soil, cocopeat, and perlite (1:1:3 ratio). Greenhouse conditions were maintained at average day and night temperatures of 25°C and 18°C, respectively, with 80% relative humidity. Seedlings were irrigated weekly with 100 mL of complete Hoagland solution. Foliar spraying with the treatments began after seedling establishment in late June and was repeated four times at 10-day intervals. Leaf samples were collected 10 days after the final application for laboratory analysis. Data were analyzed using SAS software (version 9), and means were compared using Duncan’s multiple range test at a 5% probability level.

The application of 1 mM benzyladenine resulted in the highest total chlorophyll content (1.95 mg/g fresh weight), antioxidant activity (36.02%), and peroxidase enzyme activity (1.14 U/mg protein per minute). The maximum total carotenoid content (0.14 mg/g fresh weight), total phenol (12.52 mg gallic acid/g fresh weight), total flavonoid (2.86 mg quercetin/g fresh weight), and nitrogen content (1.46%) were achieved with one mM glutamic acid. Additionally, one mM glutamic acid application led to the highest catalase enzyme activity (4.09 U/mg protein per minute), fresh weight (123.51 g), and dry weight (47.38 g).

The findings suggest that applying glutamic acid and benzyladenine at varying levels can significantly enhance the biochemical and growth characteristics of Digitalis purpurea L.

 Nepeta crispa Willd., commonly known as Mofarrah, is an endemic plant of Iran belonging to the Lamiaceae family. Its distribution in Iran is limited to the western region, specifically Hamadan province. In this study, the plant was collected from three habitats in Hamadan province, Arzanfood (Hamedan city), Gashani (Tuyserkan city), and Piste Eski (Hamedan city) at elevations of 3021, 2783, and 2686 meters above sea level, respectively, during the flowering stage. The research aimed to investigate the essential oil content and water-soluble volatile compounds (hydrosol) of N. crispa and to compare these compounds across different habitats. The study also sought to identify variations in essential oil main components and hydrosol to evaluate the influence of ecological characteristics on the plant's chemical composition.

 The plant samples were shade-dried, and essential oil was extracted using a Clevenger apparatus for 3 hours. Water-soluble volatile compounds (hydrosol) were collected by leaving the exit part of the Clevenger open to condense vapor into liquid. The hydrosol was then separated using ethyl acetate solvent in a separatory funnel. The essential oil and hydrosol were analyzed using GC-FID and GC/MS.

 The essential oil yields from the Arzanfood, Gashani, and Piste Eski samples were 2.01%, 1.97%, and 1.82% (w/w), respectively. The concentration of water-soluble volatile compounds in the hydrosol were 0.15, 0.11, and 0.12 grams per 100 ml, respectively. The primary compounds identified in the essential oil were 1,8-cineole (49.4%, 48.5%, and 60%), 4aα,7β,7aα-nepetalactone (27%, 3.7%, and 8.3%), 4aα,7α,7aα-nepetalactone (0.1%, 23.5%, and 7.2%), and β-pinene (4.3%, 5.4%, and 6.1%) for Arzanfood, Gashani, and Piste Eski, respectively. In the hydrosol, the main components were 4aα,7β,7aα-nepetalactone (74.1%, 40.3%, and 57.1%) and α-pinene oxide (4.6%, 7.1%, and 5.2%).

 The variation in essential oil yield across different habitats highlights the impact of ecological factors on the quantity of essential oil. The highest essential oil yield (2.01%) was observed in the Arzanfood sample, which also has the highest elevation among the studied regions. A total of 22 compounds were identified in the essential oil, with 18, 20, and 17 compounds detected in the Arzanfood, Gashani, and Piste Eski samples, respectively. The dominant compound in the essential oil was 1,8-cineole, while 4aα,7β,7aα-nepetalactone was the most abundant compound in the hydrosol. This study marks the first report on the hydrosol analysis of N. crispa from different habitats.

The poultry industry plays a significant role in the human food chain, with its products contributing substantially to meeting protein requirements. In modern poultry production systems, birds are often raised under high-density conditions for economic efficiency. However, increased density and other factors can lead to various stresses, particularly heat stress, negatively impacting growth, performance, and overall health. Heat stress compromises the birds' defense mechanisms, making them more susceptible to diseases. Special feed additives are often employed to enhance performance and feed conversion efficiency to mitigate the adverse effects. Heat stress is a major challenge in the poultry industry, causing significant economic losses, especially in tropical climates. In broilers, it leads to reduced growth rates, intestinal tissue damage, immune suppression, and fat oxidation, ultimately diminishing economic performance. This study investigated the effects of dietary flixweed supplementation on performance, carcass traits, serum biochemistry, and Jejunum histology in broilers reared under high ambient temperatures. 500-day-old male broilers (Ross 308) were randomly assigned to five treatments with four replicates (25 chicks per replicate). The dietary treatments included: 1- Positive control (PC): Standard diet without additives under normal conditions, 2- Negative control (NC): Standard diet without additives under high ambient temperature conditions, 3- NC + 0.2% Vitamin C complex, 4- NC + 0.5% flixweed seed, and 5-NC + 1% flixweed seed. Body weight and feed consumption were measured at the end of the initial, growth, and final periods. On day 42, one bird from each replicate was randomly selected for blood collection via the wing vein. Blood samples were collected into Venoject tubes containing 0.5 cc of the anticoagulant ethylenediamine tetraacetic acid (EDTA) for hematological analysis. Dietary treatments under heat stress significantly affected body weight at 24 and 42 days of age compared to the NC group, though no differences were observed compared to the PC group. Body weight at 1 and 10 days of age was unaffected by treatments (P < 0.05). The PC group exhibited higher body weights at 24 and 42 days than other treatments. Average daily gain, feed conversion ratio, and feed intake during 10-24 days, 24-42 days, and 1-42 days differed significantly among treatments. Serum total cholesterol, triglyceride levels, and jejunum histology traits were also significantly influenced by the treatments. Notably, supplementing the NC diet with 0.5% flixweed improved performance traits in the NC group. Under high ambient temperature conditions, dietary supplementation with 0.5% flixweed can enhance performance traits in broilers, making it a viable feed additive for improving productivity under heat stress.

Among the 16 species of Satureja in Iran, 10 are endemic, including S. bachtiarica, S. khuzistanica, S. intermedia, S. sahendica, S. isophylla, S. rechingeri, S. edmondi, S. kallarica, S. atropatana, and S. kermanshahensis. Satureja sahendica Bornm. is a perennial plant with essential oil widely used in the pharmaceutical, food, health, and cosmetic industries. Its antiviral properties have also been documented. Drought stress is one of the most significant environmental challenges for plants, leading to reduced water absorption, stomatal conductance, transpiration, and photosynthesis, while also disrupting hormonal balance. Plants adopt various mechanisms to mitigate drought stress, such as increasing osmotic regulators like sugars, proline amino acids, and proteins. Drought conditions typically decrease chlorophyll content while increasing carotenoids. Additionally, oxidative stress intensifies under drought, leading to the accumulation of reactive oxygen species such as catalase, superoxide dismutase, and ascorbate peroxidase in chloroplasts and mitochondria. Mycorrhizal fungi play a crucial role in enhancing root absorption, regulating water movement within host plants, and ultimately improving tissue water uptake and leaf physiology.

This experiment was conducted using a split-plot design within a randomized complete block design (RCBD) with three replications at the Research Institute of Forests and Rangelands during 2015–2016. The main factor was irrigation treatment, consisting of full irrigation (control), irrigation interruption at the stem stage (resumed at the budding stage), irrigation interruption at the budding stage (no irrigation until the end of the flowering period), and irrigation interruption at the 50% flowering stage (no irrigation until the end of flowering). The secondary factor was biological fertilizer application, which included no biofertilizer (control), inoculation with Glomus intraradices, inoculation with Glomus mosseae, and inoculation with Glomus mosseae + Glomus intraradices. Throughout the growth period, irrigation was maintained at 80–90% of field capacity, and drought treatments were applied based on plant morphology. The biofertilizers contained mycorrhizal fungi (Glomus intraradices and Glomus mosseae) in the form of active fungal structures, including spores, hyphae, and roots. Before transplanting the seedlings, 10 grams of biofertilizer, containing 400 to 500 active fungal units, was applied to each planting hole.

The interaction effect of drought stress and mycorrhiza was significant at the 1% probability level for protein, catalase, superoxide dismutase, peroxidase, chlorophyll a, total chlorophyll, proline, polyphenol oxidase, soluble sugars, essential oil percentage, essential oil yield, and flowering shoot yield, while its effect on carotenoid and total phenol was significant at the 5% level. The results indicated that the yield of p-cymene, γ-terpinene, and thymol was significantly influenced at the 1% level by the triple interaction of year, drought stress, and mycorrhiza. Mean comparisons revealed that catalase, superoxide dismutase, chlorophyll b, proline, total phenol, essential oil percentage, and essential oil yield were higher in the second year. Regarding drought stress, the highest flowering shoot yield was observed under full irrigation and moisture stress applied at the full flowering stage. Mycorrhizal treatment comparisons showed that the highest malondialdehyde release occurred in plants without inoculation and those treated with the combination of Glomus intraradices + Glomus mosseae. Essential oil analysis revealed that the highest percentage (2.23%) was obtained in the budding stage treatment with G. mosseae, while the highest essential oil yield (51.78 kg/ha) was recorded under full irrigation with G. intraradices inoculation. The triple interaction (year × drought stress × mycorrhiza) analysis showed that in the first year, the highest thymol yield (74.59%) resulted from full irrigation combined with G. mosseae inoculation.

Therefore, it can be concluded that the application of biological fertilizers effectively mitigated the effects of drought stress, leading to an increase in both the essential oil percentage and thymol content.

Lemongrass (Cymbopogon citratus (DC.) Stapf), a perennial plant from the Gramineae family, is renowned for its rich polyphenol compounds, having significant medicinal, cosmetic, and culinary applications. Enhancing the quantitative and qualitative yield of lemongrass is of considerable economic importance. Salicylic acid, a key regulator of physiological and biochemical processes, acts as an elicitor to enhance the accumulation of secondary metabolites in plants. Similarly, nitrogen plays a vital role in plant growth, improving yield quantity and quality. This study investigated the effects of nitrogen fertilizer and salicylic acid on various quantitative and qualitative traits of lemongrass. A factorial experiment based on a randomized complete block design was conducted in 2021 at the Agricultural Sciences and Natural Resources research farm of the University of Khuzestan, Ahvaz, Iran. The experiment evaluated the effects of different levels of salicylic acid (0, 10 µM, and 100 µM) and nitrogen fertilizer (0, 50, 100, 150, and 200 kg/ha from a urea source) on lemongrass. Each treatment was replicated three times. In each fertilizer treatment, 20% of the nitrogen was applied after plant establishment, with the remainder applied in four stages alongside irrigation water to minimize leaching losses based on soil nitrogen content. Salicylic acid was applied via foliar spraying using a backpack sprayer when 70% of each plot was covered by lemongrass, with a second application 15 days later. Each plot measured 3 meters in width with six planting lines, each 3 meters long, 60 cm apart, and plants within lines were spaced 40 cm apart. The soil had a silty clay texture, pH of 7.5, and electrical conductivity of 2.6 dS/m. The studied traits included chlorophyll a, b, and total chlorophyll, carotenoid content, total fresh and dry weight, antioxidant activity percentage, total phenol content, and essential oil percentage and yield. The interaction between salicylic acid and nitrogen fertilizer significantly influenced all studied traits except antioxidant activity percentage. Nitrogen fertilizer alone significantly affected antioxidant activity, with the highest percentage (89.8%) observed at 150 kg/ha of nitrogen. The highest levels of chlorophyll a, b, and total chlorophyll were achieved with no salicylic acid and 150 kg/ha of nitrogen, showing increases of 140%, 42%, and 116%, respectively, compared to the control (no salicylic acid or nitrogen). The highest total fresh and dry weight was obtained with 100 µM salicylic acid and 100 kg/ha of nitrogen, representing a 75% increase over the control. The highest essential oil percentage (0.87%) and yield (65.6 g/m²) were observed with 10 µM salicylic acid and 150 kg/ha of nitrogen. In contrast, the lowest essential oil yield (18.29 g/m²) and percentage (0.45%) were recorded in the absence of salicylic acid and nitrogen and with no salicylic acid but 150 kg/ha of nitrogen, respectively. Applying nitrogen fertilizer and salicylic acid enhanced the yield and percentage of essential oil, total dry matter, and total phenol content in lemongrass leaves compared to the control. The highest essential oil yield was achieved with 10 µM salicylic acid and 150 kg/ha of nitrogen fertilizer, demonstrating the synergistic effects of these treatments on lemongrass productivity and quality.

Savory (Satureja hortensis L.) is an aromatic plant from the Lamiaceae family, known for its bioactive compounds, such as thymol and carvacrol, which possess antioxidant and antimicrobial properties. These compounds have applications in various industries, including food and pharmaceuticals. Biofertilizers like mycorrhizal and Trichoderma fungi offer advantages over chemical fertilizers. These include reducing toxic substances in the food cycle, improving soil physical and chemical properties, and being cost-effective and environmentally sustainable. Trichoderma species promote plant growth through various mechanisms, including the biological control of soil-borne diseases by producing enzymes and antibiotics and direct antagonism against pathogenic fungi. To evaluate the effect of Trichoderma harzianum on growth parameters, yield, and essential oil composition of savory in organic culture media, a factorial experiment was conducted using a completely randomized design with three replications in the Horticultural Science Greenhouse of Mohaghegh Ardabili University. The experimental treatments consisted of two factors: 1. Organic matter at three levels: Control (soil and sand mixture), Soil and sand mixture with 30% spent mushroom compost and Soil and sand mixture with 30% vermicompost. 2. Trichoderma harzianum inoculation at two levels: Inoculated and Non-inoculated (control). A 2 cm layer of coarse sand was placed at the bottom of the pots to ensure proper drainage. Savory seeds were initially grown in small pots and later transplanted to the main pots at the two- to three-leaf stage. Standard agronomic practices, such as irrigation and weeding, were maintained throughout the experiment. At the end of the study, vegetative traits (plant height, leaf area, dry weight of stem and root, number and length of secondary branches), physiological traits (chlorophyll index), nutrient content (N, K, P, Mg, Zn), and essential oil yield and composition were assessed. The results demonstrated that organic fertilizers and Trichoderma inoculation significantly improved vegetative growth and quality traits compared to the control. The highest dry weight of aerial organs (4.82 g) was recorded in the vermicompost treatment, while Trichoderma inoculation resulted in 4.87 g. The highest chlorophyll index (26.86) was observed in plants treated with Trichoderma and vermicompost. Nutrient analysis showed that Trichoderma inoculation significantly increased phosphorus (3606.3 mg/kg), nitrogen (2.55%), and magnesium (55.64 mg/kg) content. In organic substrate treatments, vermicompost application resulted in the highest levels of zinc (47.87 mg/kg), nitrogen (3.06%), and phosphorus (4143 mg/kg). The highest carvacrol content (71.90%) was observed in Trichoderma-inoculated plants, while the highest essential oil yield (0.599 mL per pot) was found in plants treated with Trichoderma and vermicompost. The findings suggest that organic substrates combined with Trichoderma fungus can serve as an effective alternative to chemical fertilizers, enhancing both yield and essential oil quality in the organic cultivation of savory.

 Valeriana, a genus in the Caprifoliaceae family, includes several species, notably Valeriana officinalis L. (valerian). Valerian root extract contains various bioactive compounds, including valerenic acid, valeranone, valepotriates, and gamma-aminobutyric acid, which have been widely used as sedatives to treat sleep disorders such as insomnia. This study aimed to evaluate the induction of valerian hairy roots using three different strains of Agrobacterium rhizogenes (A13, R1601, and LBA9402) under four different growth media compositions: (1) MS full strength, (2) MS supplemented with KH2PO4, NH4NO3, and KNO3, (3) MS supplemented with KH2PO4, NH4NO3, KNO3, and CaCl2, and (4) a medium containing MgSO4, microelements, Na2EDTA, FeSO4, and vitamins.

 This study was a factorial experiment based on a completely randomized design with eight replications under laboratory conditions. Seeds of V. officinalis were obtained from a commercial supplier (Pakan Seed Company, Isfahan, Iran) and germinated under greenhouse conditions. Before sowing, seeds were washed with tap water and distilled water. Seeds that settled at the bottom of the washing vessel were selected as they were expected to be the most viable. They were soaked overnight in water before being washed with a 10% detergent solution for 10 minutes, followed by surface disinfection with 70% ethanol for 30 seconds and 6% NaOCl for 5 minutes. After rinsing four times with sterile water, the seeds were germinated on solid Schulz medium, without growth regulators, at 25°C under a 16-hour light/8-hour dark photoperiod (45 µE m⁻² S⁻¹). Hairy root induction was performed using spray and leaf disc methods, and transformation was confirmed by polymerase chain reaction (PCR) analysis for the presence of rolB and virD genes. Hairy root induction rate, lateral branches per centimeter, number of hairy roots per explant, and dry weight of hairy roots were measured after 60 days. Essential oil was extracted by hydro-distillation and analyzed using gas chromatography (GC) and gas chromatography-mass spectrometry (GC/MS).

 The study confirmed that the tested A. rhizogenes strains could induce hairy roots in valerian. The fastest hairy root emergence was observed in explants inoculated with strain A13, occurring within 10 days. The highest induction rate (92%), hairy root dry weight (272 mg), and number of hairy roots per explant (19.2) were obtained in leaf explants inoculated with the A13 strain and cultured in MS medium supplemented with KH2PO4, NH4NO3, KNO3, and CaCl2. No significant differences were observed in the morphological traits of hairy roots induced by different A. rhizogenes strains.

The findings indicate that growth media composition, appropriate A. rhizogenes strain, and optimized growth conditions enhanced hairy root biomass production. The A13 strain was the most effective in promoting mass hairy root production, particularly in MS medium supplemented with KH2PO4, NH4NO3, KNO3, and CaCl2. Given the complex physiological processes involved, valerian hairy root cultures can preserve valeric acid found in vegetative tissues. Future research should focus on identifying the optimal growth media conditions that maximize vegetative growth and secondary metabolite production in valerian.

Extracts from various medicinal plants contain valuable bioactive and phytochemical compounds, including polyphenols and flavonoids, known for their potent antioxidant, antimicrobial, anticancer, and antidiabetic properties. The caper plant (Capparis spinose L.), native to Hirmand City, is a rich source of bioactive compounds such as saccharides, glycosides, flavonoids, alkaloids, phenolic acids, terpenoids, fatty acids, vitamins, and steroids. Novel extraction methods, such as ultrasound-assisted extraction, offer significant advantages over traditional techniques like Soxhlet and maceration. Ultrasound facilitates efficient extraction, reduces processing time, and preserves heat-sensitive bioactive compounds. This study aimed to assess the efficacy of ultrasound waves in extracting phenolic and antioxidant compounds from caper leaves.

Response Surface Methodology (RSM) and Box–Behnken Design (BBD) were employed to optimize two extraction parameters for phenolic and antioxidant compounds from caper leaves using ethanolic and aqueous solvents: extraction time (15, 30, 45 min) and ultrasound power (100, 200, 300 watts). Design Expert software suggested 13 treatments for extraction. Dried plant leaves were ground and dissolved in 70% ethanol (for alcoholic extraction) or distilled water (for aqueous extraction) at 1:4 w/v. Ultrasonic bath treatment with a constant frequency of 40 kHz was applied. Alcoholic extracts were concentrated using a rotary evaporator under vacuum, while aqueous extracts were processed in a vacuum oven at 40°C. The antioxidant activity of the extracts was assessed using the Folin-Ciocalteu colorimetric method for total phenolic content (TPC) and the DPPH free radical inhibition method, determining the half-maximal inhibitory concentration (IC50) index. Mean comparisons between the antioxidant test results of aqueous and alcoholic extracts were performed using the Mann-Whitney U test in a completely randomized design at α = 5% with SAS software version 9.1.

Statistical analysis using the RSM model indicated that the quadratic model was the best fit for the measured parameters. The significant effects of time and ultrasound power on phenolic compound extraction and DPPH free radical inhibition ability in alcoholic extracts were determined with regression coefficients of 0.99 and 0.98, respectively. For aqueous extracts, the regression coefficients were 0.98 and 0.99, respectively. The TPC of caper leaf extracts obtained via ultrasound-assisted extraction with ethanol and distilled water solvents was 20.77±0.32 mg/g and 17.53±0.54 mg/g, respectively. The IC50 values of ethanol and distilled water extracts were 13.16±0.60 μg/ml and 20.42±0.81 μg/ml, respectively. The optimal extraction conditions were identified as an extraction time of 45 minutes and an ultrasound power of 300 watts. Under these conditions, the TPC values were 27.4 mg/g (ethanolic extract) and 23.8 mg/g (aqueous extract), while the IC50 values were 8.1 μg/ml and 10.8 μg/ml, respectively.

Ultrasound-assisted extraction is highly efficient for both alcoholic and aqueous extraction of phenolic and antioxidant compounds from caper leaves. A direct correlation was observed between TPC levels and DPPH free radical inhibition ability. Alcoholic extracts contained higher phenolic compound concentrations and exhibited higher antioxidant activity than aqueous extracts.

Milk thistle (Silybum marianum) is an annual or biennial herbaceous plant belonging to the Asteraceae family. The key bioactive compounds of this medicinal plant are flavonoids, which are primarily stored in the fruit (seed) and appear yellow. Among them, silymarin exhibits potent anti-inflammatory properties and plays a role in cancer prevention by affecting the vascular structure of prostate, breast, ovarian, liver, and leukemia cancer tissues. Biotechnological approaches, particularly tissue and cell culture techniques, serve as valuable complementary methods for the commercial production of plant-derived compounds. This study aimed to determine the optimal method for producing sterile S. marianum seedlings and to evaluate the effects of genotype, explant type, and growth regulators on callus induction, growth, and embryogenic callus formation.

In this study, five genotypes (Hungary, Borazjan, Fereydon Kenar, Jolgeh Khalaj, and Moghan) were evaluated using three different seed disinfection methods in a factorial experiment based on a completely randomized design (CRD) with three replications. Seed germination and sterile seedling production were conducted in water and agar culture media without growth regulators, under dark conditions at 25°C. Subsequently, an experiment was performed using two genotypes (Hungary and Borazjan), cotyledon and hypocotyl explants, Murashige and Skoog (MS) medium, and growth regulators 2,4-D (1, 2.5, and 5 mg/L) and BAP (0.25 and 0.5 mg/L) in a factorial experiment based on completely random design under dark conditions. After 30 days, the induced callus was transferred to MS medium with half the initial hormone concentrations. Callus diameter was assessed using the Hochrony Berz method, while callus fresh weight, the number of embryogenic calluses, and the number of somatic embryos per callus in cotyledon explants were measured 30 days post-culture. Calluses were freeze-dried, and their dry weight was also recorded.

The optimal method for producing sterile S. marianum seedlings involved treatment with Tween-20 solution, 70% ethanol, hydrogen peroxide, and sterile distilled water, followed by cultivation in water and agar medium without growth regulators. Analysis of variance for callus diameter, fresh weight, and dry weight indicated that the best conditions for callus induction were the Borazjan genotype, cotyledon explant, 1 mg/L 2,4-D and 0.5 mg/L BAP. Embryogenic callus formation occurred exclusively in cotyledon explants. Variance analysis of embryogenic callus production and the number of somatic embryos per callus revealed that optimal conditions for embryogenic callus formation were achieved using the Hungarian genotype with 5 mg/L 2,4-D and 0.25 mg/L BAP.

Based on the results, the most effective disinfectants for S. marianum seeds were Tween-20 solution, 70% ethanol, hydrogen peroxide, and sterile distilled water. For optimal callus production, cotyledon explants and low concentrations of auxin, such as 2,4-D, were preferable. In embryogenic callus formation, improved cultivars like Hungary outperformed native genotypes. Additionally, cotyledon explants were more suitable than hypocotyl explants, and high concentrations of auxin (2,4-D) combined with low concentrations of cytokinin (BAP) provided the best results.

Water availability is one of the most critical climatic factors influencing plant distribution worldwide. Drought stress, resulting from insufficient water availability, can induce plant morphophysiological, biochemical, and functional changes. Seaweed contains a high percentage of polymer compounds capable of absorbing water molecules and forming a gel-like structure. Additionally, its rich composition of salts and essential minerals fulfills plant nutrient requirements, promotes growth and yield, enhances resistance to environmental stress, improves nutrient uptake from the soil, and boosts antioxidant properties. Tarragon (Artemisia dracunculus L.) is an herb widely used as a flavoring agent in the food industry, with its essential oil playing a key role in canning and perfumery. Because seaweed extract serves as a natural biofertilizer, providing essential nutrients and plant growth hormones while being environmentally friendly, it represents a viable alternative to chemical fertilizers. Moreover, it enhances plant resilience to various environmental stresses and contributes to sustainable food production. This study aims to investigate the effects of seaweed extract on the growth and biochemical characteristics of tarragon under drought stress conditions.

This study was conducted to investigate the growth, physiological, and biochemical characteristics of the medicinal plant tarragon (Artemisia dracunculus L.) under drought stress at four levels (100%, 80%, 60%, and 40% field capacity) and foliar application of aqueous Sargassum seaweed extract at three concentrations (0 g/L [control], 1 g/L, and 2 g/L). The experiment was carried out in the spring of 2023 in a greenhouse located in Damavand, using a factorial arrangement based on a completely randomized design with three replications. Four-leaf tarragon seedlings were obtained from the training farm of Damavand Technical and Vocational School and transplanted into three-liter pots. After a 10-day establishment period, drought stress was applied for 45 days, with foliar spraying of seaweed extract performed every two weeks, starting simultaneously with the onset of drought stress. Soil moisture levels in the pots were monitored daily by weighing them, and water was added as needed to maintain the target field capacity for each treatment. Plant sampling was conducted one week to 10 days after the completion of treatments, coinciding with the transition from vegetative to reproductive growth. Morphophysiological traits, including fresh and dry biomass, plant height, and the number of secondary branches, were measured. Additionally, biochemical parameters such as proline content, soluble carbohydrates, total phenol and flavonoid content, antioxidant activity, and essential oil yield and percentage were analyzed.

The results indicated that under severe drought stress (40% field capacity) and in the absence of seaweed extract application, there was a significant reduction in morphophysiological traits, including plant height, main stem diameter, number of secondary branches, fresh and dry weight of aerial parts, and photosynthetic pigments (chlorophyll a, chlorophyll b, and total chlorophyll). However, the application of seaweed extract mitigated the adverse effects of drought stress on tarragon. Under mild drought stress (60% field capacity) without seaweed extract application, the highest levels of total phenol (82 mg/g gallic acid), total flavonoid (64.33 mg/g quercetin), antioxidant activity (76%), and essential oil yield and percentage were observed. Drought stress also enhanced the activity of antioxidant enzymes, leading to increased synthesis of soluble carbohydrates and proline compared to the control. Among the tested seaweed extract concentrations, the application of 2 g/L had the most significant positive impact on the evaluated traits, further improving plant resilience and biochemical responses under drought-stress conditions.

The overall findings of this study indicate that tarragon exhibits limited resistance to drought stress, with a noticeable decline in yield as stress intensity increases. Under drought conditions, the application of seaweed extract, particularly at a concentration of 2 g/L, effectively mitigated the adverse effects of stress by enhancing morphophysiological and phytochemical traits, including total phenol, flavonoid content, and essential oil yield. In most cases, the difference between 2 g/L and 1 g/L of seaweed extract was statistically significant, with 2 g/L demonstrating superior effectiveness. Therefore, the application of 2 g/L seaweed extract is recommended to improve drought tolerance and maintain yield in tarragon under water-limited conditions.

Allium jesdianum is a valuable medicinal and edible plant belonging to the Alliaceae family and is native to Iran. However, due to excessive harvesting in its natural habitat, it is currently endangered. This study aimed to promote the cultivation, conservation, and habitat restoration of this endangered species. To ensure its sustainability, wild ecotypes were cultivated in controlled agricultural environments, and the effects of plant nutrition and gibberellic acid on reproductive success and overall yield were evaluated.

A randomized complete block experiment with three replications was conducted during the 2021–2022 growing season at the research farm of Lorestan University. The experimental treatments included cow manure at two levels (0 and 40 t/ha), NPK biofertilizer (Azotobarvar-1, Potabarvar-2, and Phosphatebarvar-2) at two levels (0 and 100 g/ha), and gibberellic acid (GA₃) at two levels (0 and 250 ppm). Bulbs were collected from their natural highland habitat near the research site and cultivated in the field after being inoculated with NPK biofertilizer and gibberellic acid. Various morphological and yield-related traits were measured, including plant height, fresh and dry leaf weight, weight and diameter of mother and daughter bulbs, daughter bulb production, economic yield, and biological yield. Data were analyzed using SAS 9.4 software, and treatment means were compared using the LSD test at a 5% significance level.

Applying cow manure, NPK biofertilizer, and gibberellic acid individually or in combination significantly influenced most vegetative and yield-related traits. However, the number of leaves per plant showed no significant variation. The highest plant height (26.53 cm), fresh leaf weight (8.24 g per plant), and dry leaf weight (2.84 g per plant) were recorded in the treatment combining cow manure, NPK biofertilizer, and gibberellic acid. Fertilizer and gibberellic acid application led to an approximately 2.5-fold increase in fresh leaf yield and an 18% improvement in biological yield compared to the control. The combination of cow manure and biological fertilizer had the most substantial impact on plant growth parameters. The weight and diameter of the mother bulb were significantly influenced by both the main effects and their interactions, with the highest values (3.58 g per plant and 22.52 mm) observed under the combined application of cow manure, biological fertilizer, and gibberellic acid. Similarly, the weight and diameter of daughter bulbs followed the same pattern. Reproductive success in A. jesdianum was significantly improved with the combined application of cow manure, biological fertilizer, and gibberellic acid. This treatment resulted in the highest bulb yield, averaging 13.33 bulbs per unit area.

The results indicate that the integrated application of cow manure, NPK biofertilizer, and gibberellic acid significantly enhances plant yield and daughter bulb production. Therefore, this approach is recommended for farmers seeking to improve A. jesdianum cultivation while reducing dependence on chemical fertilizers.