Phytoremediation potential of moso bamboo (Phyllostachys pubescens) for zinc and ultrastructure changes under zinc toxicity
This study has investigated toxicity of Zn and phytoremediation ability in shoot of moso bamboo. In hydroponic experiment the plants showed high Zn torelence up to application of 400 µM, while there was a general trend of decline in the roots and shoot biomass. Maximum concentration of 1594 mg kg–1 was observed in shoot after treating with 100 µM Zn. The shoot/root ratio reached the level of 0.27 under 10 µM zinc stress. Transmission electron microscopy revealed that electron-dense granules in vacuoles and structure of leaf cells were significantly effected by 200 µM of Zn. However, mitochondria and thylakoid membrane arrangement did not alter. Using scanning electron microscopy, Zn-related changes in the structure of the stoma were uncovered and crystal particles probably of Zinc were observed in stem.
BIOACCUMULATION AND TOXICITY OF Cu AND Zn IN HYDRILLA VERTICILLATA(LINN.F.) ROYLE
In the present study,Hydrilla verticillata(Linn.f.) Royle,a submerged macrophyte widely distributed in China was used as experimental material.Cu and Zn,essential elements for the normal development and growth of plants were selected as the stress factors.H.verticillata was cultivated in water containing elevated concentrations of Cu and Zn(up to 10 mg/L) for 7d under lab condition.The bioaccumulation of Cu and Zn were determined by Inductively Coupled Plasma-Atomic Emission Spectrometry(ICP) and their environmental toxicology in H.verticillata was studied.The results suggested that contents of Cu and Zn in H.verticillata were nearly in linear increase with rise of metal concentration in solution,and statistical analysis indicated that they all reached significant positive levels(R_(Cu)=0.9875,P0.01;R_(Zn)=0.9990,P0.01).It was found that H.verticillata fronds were able to absorb and accumulate Cu and Zn differently,and the bioaccumulation factor ranged from 571 to 1328 and 346 to 830,respectively.The absorption capability of H.verticillata to Cu was better than to Zn and low heavy metal concentration was good for absorption.Sequential extraction indicated that the ratio of different Cu and Zn chemical forms were different markedly,of which NaCl extractable Zn,2% HAc extractable Cu were predominated as compared with the other 5 forms;which could be seen in the following order: Cu: F_(HAc) F_(HCl) F_(NaCl) F_(Water) F_(Ethanol) F_(Residue);Zn:F_(NaCl) F_(HAc)F_(HCl)F_(Ethanol)F_(Residue)F_(Water).Auto fluorescent range narrowed;both peak value and average intensity decreased in leaf of H.verticillata under Cu and Zn stress.Scanning and transmission electron microscope observation indicated that Cu and Zn imposed injury action on morphological structure and ultrastructure of leaf cells,such as distortion of cell wall and cell shape,disaggregation of nucleolus,agglutination and disappearance of chromatin of nucleus,disruption of nuclear membrane,swelling of thylakoids and breakage of chloroplast envelope,decreasing of cristae quantity and vacuolization of mitochondria.The conclusion was that there was a significant dose-effect between bioaccumulation and toxicity.Namely,the more the pollutant contents in H.verticillata,the severer the toxicity to the plant.
A comparison of phytoremediation capability of selected plant species for given trace elements.
In our experiment, As, Cd, Pb, and Zn remediation possibilities on medium contaminated soil were investigated. Seven plant species with a different trace element accumulation capacity and remediation potential were compared. We found good accumulation capabilities and remediation effectiveness of Salix dasyclados similar to studied hyperaccumulators (Arabidopsis halleri and Thlaspi caerulescens). We have noticed better remediation capability in willow compared to poplar for most of the elements considered in this experiment. On the contrary, poplar species were able to remove a larger portion of Pb as opposed to other species. Nevertheless, the removed volume was very small. The elements found in plant biomass depend substantially on the availability of these elements in the soil. Different element concentrations were determined in natural soil solution and by inorganic salt solution extraction (0.01 molL(-1) CaCl(2)). Extracted content almost exceeded the element concentration in the soil solution. Element concentrations in soil solution were not significantly affected by sampling time.