Intraspecific divergence in essential oil content, composition and genes expression patterns of monoterpene synthesis in Origanum vulgare subsp. vulgare and subsp. gracile under salinity stress.

BACKGROUND: Oregano (Origanum vulgare L.), one of the important medicinal plants in the world, has valuable pharmacological compounds with antimicrobial, antiviral, antioxidant, anti-inflammatory, antispasmodic, antiurolithic, antiproliferative and neuroprotective activities. Phenolic monoterpenes such as thymol and carvacrol with many medical importance are found in Oregano essential oil. The biosynthesis of these compounds is carried out through the methyl erythritol-4 phosphate (MEP) pathway. Environmental stresses such as salinity might improve the secondary metabolites in medicinal plants. The influence of salinity stress (0 (control), 25, 50 and 100 mM NaCl) on the essential oil content, composition and expression of 1-deoxy-D-xylulose-5-phosphate reductoisomerase (DXR), γ-terpinene synthase (Ovtps2) and cytochrome P450 monooxygenases (CYP71D180) genes involved in thymol and carvacrol biosynthesis, was investigated in two oregano subspecies (vulgare and gracile). RESULTS: Essential oil content was increased at low NaCl concentration (25 mM) compared with non-stress conditions, whereas it was decreased as salinity stress intensified (50 and 100 mM). Essential oil content was significantly higher in subsp. gracile than subsp. vulgare. The highest (0.20 mL pot-1) and lowest (0.06 mL pot-1) amount of essential oil yield was obtained in subsp. gracile at 25 and 100 mM NaCl, respectively. The content of carvacrol, as the main component of essential oil, decreased with increasing salinity level in subsp. gracile, but increased in subsp. vulgare. The highest expression of DXR, Ovtps2 and CYP71D180 genes was observed at 50 mM NaCl in subsp. vulgare. While, in subsp. gracile, the expression of the mentioned genes decreased with increasing salinity levels. A positive correlation was obtained between the expression of DXR, Ovtps2 and CYP71D180 genes with carvacrol content in both subspecies. On the other hand, a negative correlation was found between the expression of CYP71D180 and carvacrol content in subsp. gracile. CONCLUSIONS: The findings of this study demonstrated that both oregano subspecies can tolerate NaCl salinity up to 50 mM without significant reduction in essential oil yield. Also, moderate salinity stress (50 mM NaCl) in subsp. vulgare might increase the carvacrol content partly via increment the expression levels of DXR, Ovtps2 and CYP71D180 genes.

Wastewater irrigation: An opportunity for improving soil phosphorus availability; PHREEQC modeling and adsorption studies.

Wastewater, an alternative supply of water and nutrients, is being allocated as a priority for human population sustainability in arid and semi-arid regions. This work proposes phosphorus (P), a vital growth-limiting nutrient, adsorption behavior in wastewater irrigated agricultural soils in comparison to non-irrigated soils using laboratory batch experiments. The adsorption mechanism was assessed using different adsorption isotherm models. Saturation indices were modeled, using the hydro-geochemical transport code PHREEQC and MINTEQ geochemical software. Phosphorus buffering parameters were also calculated based on the standard equations. The equilibrium data were well fitted with the Freundlich isotherm model. The physical adsorption mechanism was found based on the calculated isotherm parameters. The maximum adsorption capacity was two times more in non-wastewater irrigated soils than irrigated. Results highlighted the effectiveness of wastewater irrigation in P availability in soil. Based on the PHREEQC modeling data, precipitation of Pb and Zn mineral phases was probable in soils by wastewater influence. Meanwhile, the precipitation of stable calcium phases, that affect the P sorption and/or co-precipitation, in non-wastewater irrigated soils was highlighted in the PHREEQC calculations. The standard buffer capacity (SBC) was 43 and 64 L kg-1 in wastewater irrigated soils and non-irrigated soils, respectively. Findings of the present study demonstrate the importance of wastewater reuse opportunities for agricultural application, especially soil P availability, and are helpful to minimize the environmental impacts of wastewater and solid waste.

Increasing medicinal and phytochemical compounds of coneflower (Echinacea purpurea L.) as affected by NO3-/NH4+ ratio and perlite particle size in hydroponics.

Medicinal plants are considered as one of the most important sources of chemical compounds, so preparing a suitable culture media for medicinal plant growth is a critical factor. The present study is aimed to improve the caffeic acid derivatives and alkylamides percentages of Echinacea purpurea root extract in hydroponic culture media with different perlite particle size and NO3-/NH4+ ratios. Perlite particle size in the growing media was varied as very coarse perlite (more than 2 mm), coarse perlite (1.5-2 mm), medium perlite (1-1.5 mm), fine perlite (0.5-1 mm), and very fine perlite (less than 0.5 mm) in different ratios to peat moss (including pure perlite, 50:50 v/v, 30:70 v/v, and pure peat moss). Two NO3-/NH4+ ratios (90:10 and 70:30) were tested in each growing media. All phytochemical analyses were performed according to standard methods using high performance liquid chromatography (HPLC). It was found that the E. purpurea grown in the medium containing very fine-grade perlite with 50:50 v/v perlite to peat moss ratio had the maximum caffeic acid derivatives, including chicoric acid (17 mg g-1 DW), caftaric acid (6.3 mg g-1 DW), chlorogenic acid (0.93 mg g-1 DW), cynarin (0.84 mg g-1 DW), and echinacoside (0.73 mg g-1 DW), as well as, alkylamides (54.21%). The percentages of these phytochemical compounds increased by decreasing perlite particle size and increasing of NO3-/NH4+ ratio. The major alkylamide in the E. purpurea root extract was dodeca-2E, 4E, 8Z-10 (E/Z)-tetraenoic acid isobutylamide in all treatments, ranging from 31.12 to 54.21% of total dry weight. It can be concluded that optimizing hydroponic culture media and nutrient solution has significant effects on E. purpurea chemical compounds.

Optimizing hydroponic culture media and NO3-/NH4+ ratio for improving essential oil compositions of purple coneflower (Echinacea purpurea L.).

Medicinal plants represent a valuable commodity due to beneficial effects of their natural products on human health, prompting a need for finding a way to optimize/increase their production. In this study, a novel growing media with various perlite particle size and its mixture with peat moss was tested for hydroponic-based production of Echinacea purpurea medicinal plant under greenhouse conditions. The plant growth parameters such as plant height, total fresh leave weight, fresh root weight, total biomass, total chlorophyll, leaf area, and essential oil compositions were assessed. Perlite particle size in the growing media was varied from very coarse (more than 2 mm) to very fine (less than 0.5 mm), and the ratio between perlite and peat moss varied from 50:50 v/v to 30:70 v/v. In addition, two nitrate (NO3-) to ammonium (NH4+) ratios (90:10 and 70:30) were tested for each growing media. The medium containing very fine-grade perlite and 50:50 v/v perlite to peat moss ratio was found to be most optimal and beneficial for E. purpurea performance, resulting in maximal plant height, fresh and dry weight, leaf surface area, and chlorophyll content. It was also found that an increase in NO3-/NH4+ ratio caused a significant increase in plant growth parameters and increase the plant essential oil content. The major terpene hydrocarbons found in extract of E. purpurea with the best growth parameters were germacrene D (51%), myrcene (15%), α-pinene (12%), ß-caryophyllene (11%), and 1-Pentadecene (4.4%), respectively. The percentages of these terpene hydrocarbons were increased by increasing of NO3-/NH4+ ratio. It can be concluded that decreasing the perlite particle size and increasing the NO3-/NH4+ ratio increased the plant growth parameters and essential oil compositions in E. purpurea.

Soil nutrients status affected by simple and enriched biochar application under salinity conditions.

In order to study the effect of biochar application as simple and enriched, on the soil nutrients status in the salinity conditions, a research was conducted as a factorial arrangement based on completely randomized design (CRD) with three replicates. The biochar (grape pruning residues) was applied in three levels (0, 2% biochar, and 2% enriched biochar by rock phosphate and cow manure). Also, the salinity treatment was considered in three levels (2, 4.5, and 9 dSm-1). After treating the soil, it was incubated in polyethylene containers for a 70-day period at 25 °C and 70% field capacity moisture regime. The results showed that salinity significantly affected the soil pH, electrical conductivity (EC), calcium, magnesium, sodium, basal respiration, and nitrifying bacteria frequency (P < 0.001) and chloride concentration (P < 0.01). Also, the biochar significantly affected the pH, organic carbon, concentration of total nitrogen, phosphorous, solution potassium, sodium, iron, zinc, copper, basal respiration, and nitrifying bacteria frequency (P < 0.001) of the soil. The interaction effect of biochar and salinity levels was significant on soil sodium concentration (P < 0.01) and pH (P < 0.05). In comparison with the control treatment, the enriched biochar, decreased soil pH (about 1.4%) and increased the phosphorous, iron, and zinc up to 36%, 29%, and 36%, respectively and simple biochar increased the Nitrogen and Potassium up to 46% and 48%, respectively. In general, it was concluded that both types of the biochars lowered the sodium concentration of the soil in different salinity levels due to high potential of biochar for sodium absorption which this ability may be considered in saline soils remediation.

Distribution of phosphorous pools in western river sediments of the Urmia Lake basin, Iran.

Impact of anthropogenic loading of phosphorous (P) to an aquatic ecosystem can be qualitatively assessed by measuring the buildup and distribution of P in sediments and by differentiating bioavailable and recalcitrant P pools. Distribution of P pools in sediments is affected by the physico-chemical properties including specific elements, particle size distribution, pH, electrical conductivity (EC), and carbonate content. We applied X-ray fluorescence and scanning electron microscopy (SEM) methods to characterize sediments from western rivers in the Urmia Lake basin in Iran with a particular focus on properties that are relevant to P speciation. Phosphorous pools were sequentially extracted into operationally defined exchangeable (EXCH-P), iron and aluminum oxide-bound (Fe/Al-P), calcium-bound (Ca-P), and residual (RES-P) P pools. In river sediments, the size of P pool was found to be in the order of Ca-P > RES-P > Fe/Al-P > EXCH-P indicating small fraction of bioavailable P pool and Ca-P minerals being the most dominant P sink. Carbonate-related properties had an inverse relationship with bioavailable P pools in the river sediments studied. The principal component analysis (PCA) of the sequential extraction data with sediment properties revealed that four principal components described 82.7% of total variation. Similarly, particle size-related properties were found to have the highest eigenvalues in the first PC. Electron diffraction spectra (EDS) and X-ray fluorescence (XRF) analyses showed a largely uniform distribution of P in the upstream sediment. However, limited evidence of local enrichment of P with Fe, Al, and Ca contents was observed in the downstream river sediments. Correlation of Fe/Al-P pool size with Al2O3 and SiO2 contents indicated that P was associated with Al oxide and clay minerals in the sediment matrix. Overall, the results from this study provide insights into the variability of upstream and downstream river processes and their relationship with P pools with regard to their bioavailability. These results are expected to be useful in assessing the potential impact of P loading on the aquatic ecosystem in the Urmia Lake basin.