Elsholtzia Splendens Research Articles

Copper Phytoavailability and Uptake by Elsh{o}ltzia Splendens from Contaminated Soil as Affected by Soil Amendments

Pot and field experiments were conducted to evaluate bioavailability of Cu in contaminated paddy soil (PS) and phytoremediation potential by Elsholtzia splendens as affected by soil amendments. The results from pot experiment showed that organic manure (M) applied to the PS not only remarkably raised the H2O exchangeable Cu, which were mainly due to the increased exchangeable and organic fractions of Cu in the PS by M, but also stimulated plant growth and Cu accumulation in E. splendens. At M application rate of 5.0%, shoot Cu concentration in the plant increased by four times grown on the PS, so as to the elevated shoot Cu accumulation by three times as compared to the control. In the field trial, soil amendments by M and furnace slag (F), and soil preparations like soil capping (S) and soil discing (D) were performed in the PS. Soil capping and discing considerably declined total Cu in the PS. Application of M solely or together with F enhanced plant growth and increased H2O exchangeable Cu levels in the soil. The increased extractability of Cu in the rhizosphere of E. splendens was noted, which may have mainly attributed to the rhizospheric acidification and chelation by dissolved organic matter (DOM), thus resulting in elevating Cu uptake and accumulation by E. splendens. Amendments with organic manure plus furnace slag (MF) to the PS caused the highest exactable Cu with saturated H2O in the rhizospheric soil of E. splendens after they were grown for 170 days in the PS, thus achieving 1.74 kg Cu ha− 1 removal from the contaminated soil by the whole plant of E. splendens at one season, which is higher than those of the other soil treatments. The results indicated that application of organic manure at a proper rate could enhance Cu bioavailability and increase effectiveness of Cu phytoextraction from the contaminated soil by the metal-tolerant and accumulating plant species (E. splendens).

Gama-aminobutyric acid accumulation in Elsholtzia splendens in response to copper toxicity

A solution with different Cu supply levels was cultured to investigate gama-aminobutyric acid (GABA) accumulation in Elsholtzia splendens, a native Chinese Cu-tolerant and accumulating plant species. Increasing Cu from 0.25 to 500 micromol/L significantly enhanced levels of GABA and histidine (His), but considerably decreased levels of aspartate (Asp) and glutamate (Glu) in the leaves. The leaf Asp level negatively correlated with leaf Cu level, while leaf GABA level positively correlated with leaf Cu level. The leaf Glu level negatively correlated with leaf GABA level in Elsholtzia splendens. The depletion of leaf Glu may be related to the enhanced synthesis of leaf GABA under Cu stress.

Heavy metal uptake by arbuscular mycorrhizas of Elsholtzia splendens and the potential for phytoremediation of contaminated soil

A pot culture experiment and a field experiment were carried out separately to study heavy metal (HM) uptake from soil contaminated with Cu, Zn, Pb and Cd by Elsholtzia splendens Nakai ex F. Maekawa inoculated with arbuscular mycorrhizal (AM) fungi and the potential for phytoremediation. The HM-contaminated soil in the pot experiment was collected from the field experiment site. Two AM fungal inocula, MI containing only one AM fungal strain, Glomus caledonium 90036, and M II consisting of Gigaspora margarita ZJ37, Gigaspora decipens ZJ38, Scutellospora gilmori ZJ39, Acaulospora spp. andGlomus spp., were applied to the soil under unsterilized conditions. In the pot experiment, the plants were harvested after 24 weeks of growth. Mycorrhizal colonization rate, plant dry weight (DW) and P, Cu, Zn, Pb, Cd concentrations were determined. MI-treated plants had higher mycorrhizal colonization rates than MII-treated plants. Both MI and MII increased shoot and root DW, and MII was more effective than MI. In shoots, the highest P, Cu, Zn and Pb concentrations were all observed in the plants treated with MII, while MI decreased Zn and Pb concentrations and increased P but did not alter Cu, and Cd concentrations were not affected by either of two inocula. In roots, MII increased P, Zn, Pb concentrations but did not alter Cu and Cd, and MI did not affect P, Cu, Zn, Pb, Cd concentrations. Cu, Zn, Pb, Cd uptake into shoots and roots all increased in MII-treated plants, while in MI-treated plants, Cu and Zn uptake into shoots and Cu, Zn, Pb, Cd into roots increased but Pb and Cd uptake into shoots decreased. In general, MII was more effective than MI in promoting plant growth and HM uptake. The field experiment following the pot experiment was carried out to investigate the effects of MII under field conditions. The 45-day-old nonmycorrhizal and MII-colonized seedlings of E. splendens were transplanted to HM-contaminated plots and harvested after 5 months. MII-inoculation increased shoot DW and shoot P, Cu, Zn, Pb concentrations significantly but did not alter shoot Cd concentrations, which led to higher uptake of Cu, Zn, Pb, Cd by E. splendens shoots. These results indicate that the AM fungal consortium represented by MII can benefit phytoextraction of HMs and therefore play a role in phytoremediation of HM-contaminated soils.

SRXRF microprobe as a technique for studying elements distribution in Elsholtzia splendens

Elsholtzia splendens is a copper tolerant plant growing in copper mine areas in south of China and accumulates considerable heavy metals in plant tissue. In this study, synchrotron radiation X-ray fluorescence spectroscopy (SRXRF) microprobe was used to study the Cu and other elements distribution in E. splendens. The element (P, S, Cl, K, Ca, Mn, Fe, Cu, Zn) in the leaf epidermis and cross-sections of the stem and leaf could be checked by SRXRF which was considered a sensitive technique for trace element analysis. The highest Cu levels were measured in the vascular tissues of stem and petiole, while Cu levels in mesophyll were higher than in leaf epidermis. The levels of most elements were not higher in trichomes than in other tissues. It seems that the celluar compartmentation of heavy metals in epidermis and epidermal trichomes was not the general feature of all plants. There was a significant correlation between Cu and P, S, Ca in distribution, which suggested P, S, and Ca played an important role in Cu accumulation of E. splendens. Based on the significant correlation between Cu and elements Mn, Fe, and Zn in distribution, it seemed that Cu, Mn, Fe, and Zn could be transported by the same transporters with a broad substrate range.

Chelators effect on soil Cu extractability and uptake by Elsholtzia splendens.

Phytoremediation is emerging as a potential cost-effective solution for remediation of contaminated soils, and bioavailability of metal in the soil for plant uptake is an important factor for successful phytoremediation. This study aimed at investigating the ability of EDTA and citric acid for enhancing soil bioavailability of Cu and phytoremediation by Elsholtzia splendens in two types of soils contaminated with heavy metals [i.e. mined soil from copper mining area (MS), and paddy soil (PS) polluted by copper refining]. The results showed that addition of 2.5 mmol/kg EDTA significantly increased the H(2)O extractable Cu concentration from 1.20 to 15.78 mg/kg in MS and from 0.26 to 15.72 mg/kg in PS, and that shoot Cu concentration increased 4-fold and 8-fold as compared to the control. There was no significant difference between the treatment with 5.0 mmol/kg EDTA and that with 2.5 mmol/kg EDTA, probably because that 2.5 mmol/kg EDTA was enough for elevating Cu bioavailability to the maximum level. As compared with the control, citric acid had no marked effect on both soil extractable Cu and shoot Cu concentration or accumulation. The results indicated that EDTA addition can increase the potential and efficiency of Cu phytoextraction by E. splendens in polluted soils.

Growth response and phytoextraction of copper at different levels in soils by Elsholtzia splendens

Phytoremediation is a promising approach for cleaning up soils contaminated with heavy metals. Information is needed to understand growth response and uptake mechanisms of heavy metals by some plant species with exceptional capability in absorbing and superaccumulating metals from soils. Greenhouse study, field trial, and old mined area survey were conducted to evaluate growth response and Cu phytoextraction of Elsholtzia splendens in contaminated soils, which has been recently identified to be tolerant to high Cu concentration and have great potential in remediating contaminated soils. The results from this study indicate that the plant exhibited high tolerance to Cu toxicity in the soils, and normal growth was attained up to 80 mg kg −1 available soil Cu (the NH 4OAc extractable Cu) or 1000 mg kg −1 total Cu. Under the field conditions, a biomass yield of 9 ton ha −1 was recorded at the soil available Cu level of 77 mg kg −1, as estimated by the NH 4OAc extraction method. Concentration-dependent uptake of Cu by the plant occurred mainly at the early growth stage, and at the late stage, there is no difference in shoot Cu concentrations grown at different extractable soil Cu levels. The extractability of Cu from the highly polluted soil is much greater by the roots than that by the shoots. The NH 4OAc extractable Cu level in the polluted soil was reduced from 78 to 55 mg kg −1 in the soil after phytoextraction and removal of Cu by the plant species for one growth season. The depletion of extractable Cu level in the rhizosphere was noted grown in the mined area, even at high Cu levels, the NH 4OAc extractable Cu in the rhizosphere was 30% lower than that in the bulk soil. These results indicate that phytoextraction of E. splendens can effectively reduce the plant-available Cu level in the polluted soils.

Copper uptake by Elsholtzia splendens and Silene vulgaris and assessment of copper phytoavailability in contaminated soils

Tolerance and metal uptake are two essential characteristics required for phytoextraction of metals from contaminated soils. We compared tolerance and Cu uptake of Elsholtzia splendens (reported previously to be a Cu hyperaccumulator) with Silene vulgaris (the Imsbach population, a well-known Cu-tolerant excluder species), using 30 soils varying widely in total Cu concentration (19–8645 mg kg −1). We further investigated the effectiveness of different soil testing methods for predicting plant metal uptake. The results showed that both Elsholtzia splendens and Silene vulgaris were tolerant to Cu, especially Silene vulgaris. However, Elsholtzia splendens did not hyperaccumulate Cu, but behaved as a typical Cu excluder like Silene vulgaris. The concentrations of Cu in both plants correlated more closely with 1 M NH 4NO 3 extractable Cu, soil solution Cu, or effective Cu concentration determined using DGT, than with soil total Cu, EDTA extractable Cu or free Cu 2+ activity. The relationships between soil solution properties and root Cu concentrations were further investigated using multiple regression. The results showed that increasing soil solution pH increased root Cu concentration when free Cu 2+ activity was held constant, suggesting a higher phytoavailability of free Cu 2+ at a higher pH. Soil solution DOC appeared to play two contrasting roles on the phytoavailability of Cu: (1) reducing Cu availability by complexing Cu; and (2) increasing Cu availability at the same level of free Cu 2+ activity by providing a strong buffer for free Cu 2+. The results are consistent with the intensity/capacity concept for phytoavailability of metals in soils.

Anti-inflammatory activity ofElsholtzia splendens

Elsholtzia splendens Nakai has been used in North-East Asia as an ingredient of folk medicines for treating cough, headache and inflammation. The present investigation was carried out to establish its in vivo anti-inflammatory activity using several animal models of inflammation and pain. The 75% ethanol extract of the aerial part of E. splendens significantly inhibited mouse croton oil-induced, as well as arachidonic acid-induced, ear edema by oral administration (44.6% inhibition of croton oil-induced edema at 400 mg/kg). This plant material also showed significant inhibitory activity against the mouse ear edema induced by multiple treatment of phorbol ester for 3 days, which is an animal model of subchronic inflammation. In addition, E. splendens exhibited significant analgesic activity against mouse acetic acid-induced writhing (50% inhibition at 400 mg/kg), while indomethacin (5 mg/kg) demonstrated 95% inhibition. E. splendens (5-100 microg/mL) significantly inhibited PGE2 production by pre-induced cyclooxygenase-2 of lipopolysaccharide-treated RAW 264.7 cells, suggesting that cyclooxygenase-2 inhibition might be one of the cellular mechanisms of anti-inflammation.

GROWTH AND NUTRIENT COMPOSITION OF ELSHOLTZIA SPLENDENS NAKAI UNDER COPPER TOXICITY

ABSTRACT Copper (Cu) tolerance and accumulation in Elsholtzia splendens Nakai were investigated by means of hydroponic culture. Enhanced growth was observed when plants were exposed to 50 and 100 µM Cu. Copper uptake efficiency and translocation depended on Cu concentration in nutrient solution. Shoot Cu concentrations of 1133 and 3417 µg g−1 dry wt were achieved by 500 and 1000 µM Cu supply, respectively. Copper accumulation in E. splendens was accompanied by the ability to maintain the concentrations of other essential nutrients, except potassium, within the range considered sufficient for normal growth of higher plants. The results obtained suggest that E. splendens has a great potential for phytoremediation.