Exchange rates and multicommodity international trade: insights from spatial price equilibrium modeling with policy instruments via variational inequalities

In this paper, we construct a multicommodity international trade spatial price equilibrium model of special relevance to agriculture in which exchange rates are included along with policy instruments in the form of tariffs, subsidies as well as quotas. The model allows for multiple trade routes between country origin nodes and country destination nodes and these trade routes can include different modes of transportation and transport through distinct countries. We capture the impacts of exchange rates through the definition of effective path costs and identify the governing multicommodity international trade spatial price equilibrium conditions, which are then formulated as a variational inequality problem in product path flows. Existence results are established and a computational procedure presented. The illustrative numerical examples and a case study are inspired by the impacts of the war against Ukraine on agricultural trade flows and product prices. The modeling and algorithmic framework allows for the quantification of the impacts of exchange rates and various trade policies, as well as the addition or deletion of supply markets, demand markets and/or routes, on supply and demand market prices in local currencies, and on the volume of product trade flows with implications for food security.

Antimicrobial, antioxidant, cytotoxicity and LC-MS analyses of Aerva javanica: an ethnomedicinally important plant

In this study, Aerva javanica was used to extract the essential oil with notable medicinal activities. The chemical composition was investigated by high-performance liquid chromatography (HPLC) and liquid chromatography/mass spectrometry (LC-MS). Ten major chemical compounds were identified as flavonoids derivatives, dihydroxylated and glycosylated metabolites. The antimicrobial, antioxidant, and cytotoxicity activities were tested using agar well-diffusion assay, 1, 1-diphenyl-2-picrylhydrazyl (DPPH) free-radical scavenging and linoleic acid oxidation assays and hemolytic assay against human erythrocytes (RBCs), respectively. Plant extracts exhibited different extents of antimicrobial activities against selected bacterial and fungal strains; however, the essential oil displayed potent antimicrobial activity against all the tested strains. The percentage inhibition of linoleic acid oxidation and inhibitory concentration (IC50) were recorded to be in the range of 42.45-96.21% and 14.21-38.18 μg/mL, respectively. Cytotoxicity profile of A. javanica extracts and essential oil was found in the range of 5.82 to 14.47%. In conclusion, A. javanica essential oil could be a potential alternative to chemical additives in the food and pharmaceutical industries.

Analysis of biochemical compounds and differentially expressed genes of the anthocyanin biosynthetic pathway in variegated peach flowers

Variegated plants are highly valuable in the floricultural market, yet the genetic mechanism underlying this attractive phenomenon has not been completely elucidated. In this study, we identified and measured different compounds in pink and white flower petals of peach (Prunus persica) by high-performance liquid chromatography and liquid chromatography/mass spectrometry analyses. No cyanidin-based or pelargonidin-based compounds were detected in white petals, but high levels of these compounds were found in pink petals. Additionally, we sequenced and analyzed the expression of six key structural genes in the anthocyanin biosynthesis pathway (CHI, CHS, DFR, F3'H, ANS, and UFGT) in both white and pink petals. Quantitative real-time polymerase chain reaction revealed all six genes to be expressed at greatly reduced levels in white flower petals, relative to pink. No allelic variations were found in the transcribed sequences. However, alignment of transcribed and genomic sequences of the ANS gene detected alternative splicing, resulting in transcripts of 1.071 and 942 bp. Only the longer transcript was observed in white flower petals. Since ANS is the key intermediate enzyme catalyzing the colorless leucopelargonidin and leucocyanidin to substrates required for completion of anthocyanin biosynthesis, the ANS gene is implicated in flower color variegation and should be explored in future studies. This article, together with a previous transcriptome study, elucidates the mechanism underlying peach flower color variegation in terms of the key structural genes involved in anthocyanin biosynthesis.

Allelopathy of the invasive plant Bidens frondosa on the seed germination of Geum japonicum var. chinense

Five gradient concentrations (0.02, 0.04, 0.06, 0.08, and 0.10 g/mL) of leaching liquors from the roots, stems, and leaves of the invasive plant Bidens frondosa were used as conditioning fluid to examine its influence on seed germination conditions of the native plant Geum japonicum var. chinense in Huangshan. All leaching liquors of organs suppressed the seed germination of Geum japonicum var. chinense and reduced the final germination percentage and rate, and increased the germination inhibition rate, with a bimodal dependence on concentration. The leaching liquor inhibited the seed germination significantly at the concentration of 0.02 g/mL respectively. The seed germination was also inhibited as the concentration reached to 0.04 g/mL and beyond. Hence the allelopathic effects of the organs were significantly enhanced respectively. This phenomenon represented the presence of allelopathy substances in the root, stem and leaf of Bidens frondosa.