Does extensive agriculture influence the concentration of trace elements in the aquatic plant Veronica anagallis-aquatica?

The chloroplast genomes of two medicinal species (Veronica anagallis-aquatica L. and Veronica undulata Wall.) and its comparative analysis with related Veronica species

Veronica anagallis-aquatica L. and Veronica undulata Wall. are widely used ethnomedicinal plants in China. The two species have different clinical efficacies, while their extremely similar morphology and unclear interspecific relationship make it difficult to accurately identify them, leading to increased instances of mixed usage. This article reports on the complete chloroplast genomes sequence of these two species and their related Veronica species to conduct a comparative genomics analysis and phylogenetic construction. The results showed that the chloroplast (cp) genomes of Veronica exhibited typical circular quadripartite structures, with total lengths of 149,386 to 152,319 base pairs (bp), and GC content of 37.9 to 38.1%, and the number of genes was between 129-134. The total number of simple sequence repeats (SSRs) in V. anagallis-aquatica and V. undulata is 37 and 36, while V. arvensis had the highest total number of 56, predominantly characterized by A/T single bases. The vast majority of long repeat sequence types are forward repeats and palindromic repeats. Selective Ka/Ks values showed that three genes were under positive selection. Sequence differences often occur in the non-coding regions of the large single-copy region (LSC) and small single-copy region (SSC), with the lowest sequence variation in the inverted repeat regions (IR). Seven highly variable regions (trnT-GGU-psbD, rps8-rpl16, trnQ-UUG, trnN-GUU-ndhF, petL, ycf3, and ycf1) were detected, which may be potential molecular markers for identifying V. anagallis-aquatica and V. undulata. The phylogenetic tree indicates that there is a close genetic relationship between the genera Veronica and Neopicrorhiza, and V. anagallis-aquatica and V. undulata are sister groups. The molecular clock analysis results indicate that the divergence time of Veronica may occur at ∼ 9.09 Ma, and the divergence time of these two species occurs at ∼ 0.48 Ma. It is speculated that climate change may be the cause of Veronica species diversity and promote the radiation of the genus. The chloroplast genome data of nine Veronica specie provides important insights into the characteristics and evolution of the chloroplast genome of this genus, as well as the phylogenetic relationships of the genus Veronica.

Bioaccumulation and growth characteristics of Vallisneria natans (Lour.) Hara after chronic exposure to metal-contaminated sediments

Metal-contaminated sediments in lakes is a global concern that poses toxicological risk to aquatic organisms. This study performed bioassays using the submerged macrophyte, Vallisneria natans (Lour.) Hara, exposed to contaminated sediments collected from five locations in Dianchi Lake, Yunnan, China. Among the sediments collected, I_geo showed enrichment of As and Cd in Dianchi Lake sediments. In spite of enriched toxic metals at some locations, laboratory bioassays found no significant difference in leaf biomass or leaf photosynthesis rate between the sites. Root biomass and root activity showed significant differences between locations and were negatively correlated with the concentration of As, Cd, Hg, and Pb in sediment but not related to Cr. The above correlations were strongest for Hg and As, respectively. Accumulation of Cd and Pb to leaves of bioassay plants was observed, but this was not evident for As and Cr. Overall, the results indicate that V. natans can be used as a bioassay organism and measures of root toxicity are sensitive to metal concentrations present in Dianchi Lake sediments. Furthermore, the study species holds promise for use as a biomonitor of Cd and Pb sediment metal content.

Concentration Levels, Biological Enrichment Capacities and Potential Health Risk Assessment of Trace Elements in Eichhornia crassipes from Honghu Lake, China

This study investigated the concentrations of Zn, Cu, Cr, Pb, As and Cd in different tissues of E. crassipes from Honghu Lake. The total concentrations of trace elements in E. crassipes were observed in descending order: Zn (111.6162) > Cu (15.7494) > Cr (7.0466) > Pb (5.6251) > As (3.6831) > Cd (0.1941) mg/kg. The order of the bioconcentration factor (BCF) measured in E. crassipes was Zn > As > Cr > Cu > Pb > Cd > 1, indicating that E. crassipes possessed a strong biological enrichment ability to accumulate a variety of trace elements. The translocation factor (TF) values decreased in the order of Cu > Zn > Cr > As > Pb > Cd, all of which were lower than 1, which showed that the absorption of the trace elements by E. crassipes was mainly accomplished in the roots. Moreover, the health risk assessments showed that the carcinogenic and noncarcinogenic risks of the edible parts of E. crassipes were 26.1 and 4.6 times higher than the maximum acceptable value recommended by the USEPA for adults and children of approximately 39.2- and 6.9-fold, respectively. Children were more sensitive than adults. The main trace elements that led to noncarcinogenic risks were As, Cr and Cu, while Cr and As led to carcinogenic risks. The results of the Pearson correlation showed positive correlations with the concentrations of Zn, Cr and As between E. crassipes and the water as well as negative correlations of the contents of all six trace elements between E. crassipes and the sediment.