Interactions of amino acids (proline and phenylalanine) and biostimulants (salicylic acid and chitosan) on the growth and essential oil components of savory (Satureja hortensis L.)

The Role of Stress Modifier Biostimulants on Adaptive Strategy of Oregano Plant for Increasing Productivity under Water Shortage

To investigate the influence of stress modulators on the adaptive physiological responses and biomass traits of oregano under water stress conditions, a two-year (2018 and 2019) randomized complete block-designed factorial research was performed. In this study, oregano plants were treated with five stress modulators levels (CHN: chitosan, AMA: amino acids, SEW: seaweed, ASA: ascorbic acid, SAA: salicylic acid, and CON: control) at three levels of irrigation regimes (Irr40 (40), Irr60 (60) and Irr75 (75) % field capacity). The effects of water shortage and biostimulant application were evaluated on total dry weight (TDW), relative water content (RWC), essential oil production, chlorophyll, nutrient (N, K, and P), proline, total soluble sugar, polyphenol and flavonoid content, and activity of antioxidant enzymes. The result showed that under optimal irrigation conditions, oregano plants sprayed with CHN exhibited the highest dry weight (141.23 g m-2) as a morphological trait, the highest relative water content (79.34%), the most consistent concentrations of nitrogen, phosphorus and potassium (3.14, 0.39, and 1.69%, respectively), chlorophylls a and b (3.02 and 1.95 mg g-1 FW, respectively), and total phenols and total flavonoids (30.72 and 3.17 mg g-1 DW, respectively). The water deficit increased the proline content, with the greatest amount (4.17 μg g-1 FW) observed in control plants. Moreover, under moisture shortage stress conditions, the application of CHN and SEW increased the soluble sugar (27.26 μmol g-1 FW) and essential oil yield (1.80%) production, the catalase, ascorbate peroxidase, and superoxide dismutase activities (3.17, 1.18, and 63.89 μmol min-1 g-1 FW, respectively) compared to control plants. In summary, the study demonstrated that oregano plants respond positively to stress modulator treatments when subjected to moisture shortage stress, especially when treated with chitosan. The results offer promising insights for developing sustainable adaptative strategies aimed at enhancing the oregano's tolerance to water shortage, ultimately improving its productivity and biochemical traits.

Impact of Foliar Application of Amino Acids on Essential Oil Content, Odor Profile, and Flavonoid Content of Different Mint Varieties in Field Conditions

Mint is an industrial plant that is a good source of essential oil and many phenolic compounds that have several positive benefits to human health and can be used to prevent the development of many diseases. The aim of this research was to investigate the possibility of increasing essential oil and flavonoid content, changing the chemical composition of these compounds in different mint cultivars under foliar application with precursors (phenylalanine, tryptophan, and tyrosine) at two concentrations, 100 and 200 mg L^-1, to enable the possibilities for wider use of these plants when they are grown in field conditions. Spraying with phenylalanine at 100 mg L^-1 concentration increased essential oil content in Mentha piperita 'Granada' plants by 0.53 percentage units. Foliar application with tyrosine solutions at 100 mg L^-1 concentration most effectively influenced the essential oil odor profile Mentha spicata 'Crispa'. The highest number of total flavonoids was in Mentha piperita 'Swiss' sprayed with tyrosine at 100 mg L^-1 concentration. The flavonoid content depended on the mint cultivar, amino acids, and their concentration. The results showed that the effect of amino acid solutions on different secondary metabolites' quantitative and qualitative composition differed depending on the mint cultivar; therefore, amino acids and their concentrations must be selected based on the cultivar they are targeting.

Sustainable Approaches to Boost Yield and Chemical Constituents of Aromatic and Medicinal Plants by Application of Biostimulants

INTRODUCTION

Biostimulants consist of natural ingredients, metabolites of fermentation, micro-organisms, algae or plant extracts, bacteria, mushrooms, humus substances, amino acids, biomolecules, etc. Methods: In this study, all relevant English-language articles were collected. The literature was reviewed using the keywords of biostimulant, medicinal plant, aromatic plant, natural products, and pharmaceutical benefits from Google Scholar, Scopus, and PubMed databases.

RESULTS

The significant and promoting impact of biostimulants has been reported for different medicinal and aromatic plants, such as salicylic acid for ajuga, artichoke, ajwain, basil, common rue, common sage, common thyme, coneflower, coriander, dendrobium, desert Indian wheat, dragonhead, fennel, fenugreek, feverfew, ginger, groundnut, guava, henna, Iranian soda, lavender, lemon balm, lemongrass, Malabar spinach; seaweed extract on almond, bird, s eye chili; amino acids on artemisia, broccoli, chamomile, beneficial bacteria on ashwagandha; humic acid on black cumin, cannabis, chicory, garlic, gerbera, Hungarian vetch, Moldavian dragonhead, niger plant; chitosan on dragon fruit, marigold, milk thistle, etc. The suggested mechanisms include the stimulatory impacts on the activity of enzymes involved in different biosynthetic processes, the hormone-like activity of biostimulant compounds and the improvement of nutrient uptake of plants.

CONCLUSION

The current manuscript gives many examples of the potential of biostimulants for medicinal and aromatic plant production. However, further studies are needed to better understand the effectiveness of different biostimulants and foliar applications in sustainable agriculture.

The Effects of Amino acids, Phenols and Protein Hydrolysates as Biostimulants on Sustainable Crop Production and Alleviate Stresses

Biostimulants which contain substances or products including natural compounds, special formulation and microorganisms have gained a considerable attention as sustainable method for heavy metal detoxification, stimulate natural toxins, controlling diseases and pests, may increase both water and nutrient efficiency. Biostimulants are important products in modern agriculture which composed of different heterogenous classes of compounds with a broad spectrum of action to increase both qualitative and quantitative productions. Amino acids can be useful in stress defence, photosynthesis, increase nutrient uptake, pollination and fruit formation, precursors to hormones and growth parameters. Amino acids are considered as precursors and constituents of proteins, which are well-known for stimulation of cell growth. Because, they are the basic building blocks of proteins, amino acids are very important in plant growth, development and metabolite synthesis. One of the diverse, notable and the large group of secondary metabolites is phenolic compounds which have important function in regulation of the plants physiological activities, oxidation-reduction processes and photosynthesis. Protein hydrolysates contain amino acids and peptides which is one of the most important kinds of biostimulants. Protein hydrolysates have notable capability to increase crop performance, particularly under environmental stress conditions. This review article is aimed to introduce and found more about the roles of different types of biostimulants on plant growth and final yield production with considering sustainable agriculture.

Alternate gene expression profiling of monoterpenes in Hymenocrater longiflorus as a novel pharmaceutical plant under water deficit

Hymenocrater longiflorus (surahalala) is a wild plant species with potential pharmaceutical and ornamental interest. To date, the genomics of this plant is unknown and the gene expression profiling of the genes related to its metabolite has never been studied before. In order to study the responses of in vitro-grown surahalala plants to abiotic stresses and the differential expression of the genes related to its essential oils under exogenous proline application; three levels of PEG600 (0, 10, and 20%) and five levels of proline (0, 5, 10, 15, and 20 µm) were combined in the culture media. Thus, water deficit increased oxidants levels and decreased fresh weight of surahalala tissues, whereas addition of proline up to 15 µm was able to relatively compensate the negative effect of water deficit. Contrarily, high proline level (20 µm) had a negative effect on surahalala plants probably due to the stress simulation (nutrition) under high proline concentration. In addition, the best combination for achieving highest essential oils content was 10 µm proline plus 10% PEG. The expressional profiling of the genes TPS27, L3H, TPS2, TPS1, OMT and GDH3 were successfully carried out and their involvement in 1,8-cineole, carvone, α-pinene, thymol, estragole and β-Citronellol biosynthesis, respectively, was verified. In addition, our results indicated that these genes could also be involved in the synthesis of other metabolites under water deficit condition.

Biostimulants on Crops: Their Impact under Abiotic Stress Conditions

Biostimulants are agronomic tools that have been gaining importance in the reduction of fertilizer applications. They can improve the yield of cropping systems or preventing crop yield losses under abiotic stresses. Biostimulants can be composed of organic and inorganic materials and most of the components are still unknown. The characterization of the molecular mechanism of action of biostimulants can be obtained using the omics approach, which includes the determination of transcriptomic, proteomic, and metabolomic changes in treated plants. This review reports an overview of the biostimulants, taking stock on the recent molecular studies that are contributing to clarify their action mechanisms. The omics studies can provide an overall evaluation of a crop’s response, connecting the molecular changes with the physiological pathways activated and the performance with or without stress conditions. The multiple responses of plants treated with biostimulants must be correlated with the phenotype changes. In this context, it is also crucial to design an adequate experimental plan and statistical data analysis, in order to find robust correlations between biostimulant treatments and crop performance.

Effects of Biostimulants on the Chemical Composition of Essential Oil and Hydrosol of Lavandin (Lavandula x intermedia Emeric ex Loisel.) Cultivated in Tuscan-Emilian Apennines

In recent years, it has been shown that biostimulants can efficiently enhance plant metabolic processes, leading to an increased production of essential oil (EO) in aromatic plants. The present study aimed to evaluate the effects of two different commercial biostimulants composed of amino acids and seaweed extract, normally used for food organic crops, on the production and composition of EO and hydrosol of Lavandula x intermedia, cultivar "Grosso". The products were applied during 2020 growing season on lavender crops in three different locations of the Northern Italian (Emilia-Romagna Region) Apennines. Plants were harvested and EOs extracted by steam distillation and analyzed by gas chromatography. Both biostimulants affected the yield of EO per plant (+11% to +49% depending on the treatment/farm combination) without significantly changing the chemical composition of EOs and hydrosols. Conversely, the composition of EOs and hydrosols are related to the location, and the main compounds of "Grosso" cultivar, limonene, 1,8-cineole, cis-ocimene, linalool, camphor, borneol, terpinen-4-ol, and linalyl acetate, show different ratios at the experimental test sites. The differences might be due to the sunlight exposure and various maintenance of the crops over the years. In conclusion, these results suggest that the employment of biostimulants on lavandin crops do not endanger the quality of the EO while increasing biomass production and promoting the sustainability of the crop.