Assessment of chromium hyper-accumulative behaviour using biochemical analytical techniques of greenhouse cultivated Sonchus asper on tannery waste dump site soils.

Keeping the sources of pollution such as chromium (Cr) under a safe limit is a daunting challenge due to the negative impact of heavy metal bioaccumulation in vegetation and the concomitant human health exposure. We took a closer look at Sonchus asper by cultivating in the green house. It resulted in 80% germination when cultivated over nine different soils collected from the tannery dump site. The biochemical analytical techniques such as mass spectrometry indicated significant bioaccumulation of Cr in the plant tissue. As per the ICP-MS analysis, this annual herb resulted in the accumulation of 601 mg kg-1 of total Cr with 212 mg kg-1 in its shoot from soil samples containing up to 41 mg kg-1 of hexavalent Cr. The energy dispersive X-ray (EDX) spectroscopy of S. asper revealed a higher level of S element indicating a sulfate-Cr binding relation. Elevated content of Cr in soil (73,721 ± 65 mg kg-1) caused biochemical changes in the shoot of S. asper as indicated by the disappearance of Fourier transform infrared spectroscopy (FTIR) bands at 935 and 872 cm-1 and further revealing aliphatic -CH2 appearing as anti-symmetry νa(CH2) and symmetric vibration νs(CH2) at the band of 2920 and 2850 cm-1, respectively.

Photosynthesis and biochemical responses to elevated O3 in Plantago major and Sonchus oleraceus growing in a lowland habitat of northern China.

A field experiment was carried out to compare the responses to ozone (O3) in two common herbaceous plant species, Plantago major L. and Sonchus oleraceus L., by building open-top growth chambers in situ to simulate O3 stress (+O3, 85±5ppb, 9hr/day for 30days) in a lowland habitat in Inner Mongolia, Northern China. Responses to O3 of gas exchange, chlorophyll a fluorescence, leaf pigment content, antioxidant capability, soluble protein content, membrane lipid peroxidation and dark respiration (Rd) were analyzed. Results showed that elevated O3 exposure significantly reduced the light-saturated net photosynthesis (PNsat), stomatal conductance (gs) and transpiration rate (E) in both species. Although non-significant interactive effect between species and O3 on PNsat was analyzed, the reduction in PNsat in S. oleraceus might be due primarily to the higher fraction of close PSII reaction centers and impaired activities of plant mesophyll cells as evidences by decreased maximum efficiency of PSII photochemistry after dark adapted state (Fv/Fm) and unchanged intercellular CO2 concentration (Ci). Besides, biochemical analysis showed that S. oleraceus had lower antioxidant ability compared to P. major. As a result, S. oleraceus was damaged to the larger extent in terms of lipid peroxidation and visible O3 injury, indicating that S. oleraceus was more sensitive to O3 than P. major. Our results indicated that wild herbaceous plant species growing in a lowland habitat in sandy grassland were sensitive to O3 stress and S. oleraceus can be considered as one of the bio-indicators for high O3 concentration in semi-arid grassland of northern China.

Phylogeography of cliff-dwelling relicts with a highly narrow and disjunct distribution in the western Mediterranean.

PREMISE OF THE STUDY: The high biodiversity in the Baetic-Rifan hotspot of Mediterranean region is shaped by complex geological and climatic histories and has been a subject of recent intensive studies. However, very little is known about phylogenetic and biogeographic history of three rare and critically endangered cliff-dwelling species of Sonchus in section Pustulati in this region. METHODS: We investigated the genetic variation and phylogenetic relationships of populations based on nuclear (ITS/ETS) and plastid (3'trnL-ndhJ/psaI-accD) DNA sequences, and amplified fragment length polymorphisms (AFLPs). We performed a Bayesian relaxed molecular clock analysis with ITS data to estimate divergence times for major lineages. KEY RESULTS: ITS/ETS and AFLP phylogenies showed high concordance and contrasted with cpDNA data. The divergence between S. masguindalii and S. fragilis was dated at 5.48 Ma, between S. fragilis and S. pustulatus at 3.89 Ma, and between the Baetic and Rifan S. pustulatus at 1.18 Ma. Within each distribution area, AFLP data showed a relatively high genetic structuring and moderate genetic diversity, the latter being impoverished in the Baetic populations. CONCLUSIONS: Our results further confirm the hybrid origin of S. pustulatus, a critically endangered species. The origin and diversification of lineages appear to have occurred on the temporary land bridge that joined Iberian and North Africa during the Messinian Salinity Crisis (5.96-5.33 Ma) and the subsequent Zanclean flood that progressively refilled the Mediterranean Basin (5.33-3.60 Ma). The only Baetic populations of S. pustulatus most likely originated from the Rifan ones.

Behavior of native species Arrhenatherum elatius (Poaceae) and Sonchus transcaspicus (Asteraceae) exposed to a heavy metal-polluted field: plant metal concentration, phytotoxicity, and detoxification responses.

The application of vegetation cover for the phytomanagement of heavy metal-polluted soils needs prior investigation on the suitability of plant species. In this study, behaviors of Arrhenatherum elatius and Sonchus transcaspicus, two native perennial grasses that currently grow in a mine tailing, were investigated through plant metal concentration, phytotoxicity and their detoxification responses. Both of the species accumulated Ni, Cu, Cd, Co, Mn, Pb, Cr, and Zn in shoots far below criterion concentration as a hyperaccumulators; thus, neither of them were found to be hyperaccumulators. A. elatius accumulated metals in roots and then in shoots, on the contrary, in S. transcaspicus metals were preferentially accumulated in shoots. Plants exposure to such metals resulted in oxidative stress in the considered organs as indicated by the changes in chlorophyll fluorescence, chlorophyll contents, malondialdehyde (MDA) levels and antioxidative enzyme activities. A. elatius seemed to be more affected by metal-induced oxidative stress than S. transcaspicus. Correspondingly, S. transcaspicus showed a greater capacity to adapt to metal-induced oxidative stress, depending on more effective antioxidative defense mechanisms to protect itself from oxidative damage. These findings allowed us to conclude that both of these plant species could be suitable for the phytostabilization of metal-polluted soils.