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Wang M.,Zhejiang University | Duan D.C.,Zhejiang University | Xu C.,Zhejiang University | Yu M.G.,Zhejiang University | And 2 more authors.
Shengtai Xuebao/ Acta Ecologica Sinica | Year: 2015

Tea is one of the most important economic crops in China and the relevant research suggests that every year, Pb content in tea products has shown an increasing trend. Pb is also one of the most important indicators of quality and safety monitoring. Recent, research mostly focused on the resistance of plants to heavy metals was limited to short growing herbs. Reports on the study of woody plants are very rare. On the basis of these conditions tea tree was selected as research work. The objective of the present study is to find out the molecular mechanism of Pb stress resistance in roots CW of tea plants.Tea trees grown in the clean tea garden were selected for our experimental design. Tea roots were collected and washed with deionized water. Then extraction of crude CW and subsequent fractionation of CW components were carried out. Adsorption kinetics was carried out to determine the adsorption ability of different CW components to Pb stress. A total of 5 mg of CW materials or its corresponding residues was placed into a 2-ml column equipped with a filter at the bottom.The solution consisted of 15 μmol/L Pb(NO3)2 in 0.01 mol/L NaNO3 at pH 5.0.The solution was sipped by a peristaltic pump set a speed of 8 ml per 10 min after running through a 2-ml column holding the CW samples. The adsorption solutions were collected at 10-min intervals and Pb in the adsorption solutions was measured by Atomic Absorption Spectroscopy (AAS). At last the Fourier Transform infrared spectroscopy (FTIR) spectra of different CW components before and after Pb2+ adsorption was carried out to study the difference in functional groups those can interact with Pb between different CW components.The results of this study shown that the vast majority of Pb (68.42%) adsorbed in the cellulose and lignin,followed by pectin (20%) and hemicellulose2 (HC2) (5.26%).While, the contribution of HC1 was negligible. These results indicated that in the CW of roots cellulose and lignin has a greater ability to accumulate Pb as compared to pectin, HC1 and HC2. But the adsorption capacity of pectin was also very considerable. According to the FTIR spectra of CW-pectin-HC1-HC2 (CW-3) before and after Pb2+ adsorption it was found that although the cellulose and lignin contain a mass of -OH and -COOH, when they adsorbed Pb, their characteristic peaks' positions had no obvious changes. However, the positions of characteristic peaks' of C-C in cellulose polysaccharide and N-N in protein amino changed significantly, but these didn't appear at the complete CW. In summary, it was found that when CW adsorbed Pb all these functional groups in cellulose and lignin had hardly interacted with Pb. However, it was different in pectin, HC1 and HC2. For instance in pectin, when CW adsorbed Pb, -OH and -COOH characteristic peaks' positions changed significantly. It can be indicated that Pb was fixed through interactions with functional groups like -OH and -COOH in pectin. The same approach had yielded the main functional groups in HC1 and HC2 was -COOH and -OH respectively. © 2015, Ecological Society of China. All rights reserved.

Luo J.,Central South University of forestry and Technology | Ma Y.,Hangzhou Environmental Group Company Ltd | Wang H.,Central South University of forestry and Technology | Chen J.,Central South University of forestry and Technology
Electrochimica Acta | Year: 2015

Abstract Stable polypyrrole-TiO2 nanotube arrays hybrids (PPy-TNTs) have been prepared by facile anodization and potentiostatic polymerization methods. The morphology and structure of PPy-TNTs are characterized by SEM, XRD, XPS. The amount of deposited PPy can be easily adjusted by electropolymerization time. UV-vis diffuse reflection spectra show that the polypyrrole can act as visible-light photosensitizer and the electrochemical impedance spectra suggest that the formed p-n junctions between PPy and TNTs can facilitate the charge separation and transfer. The photocurrent density of PPy-TNTs under simulated solar illumination (AM1.5, 100 mW/cm2) is about 2.5 times compared with that of pristine TNTs. Incident photon to current conversion efficiency (IPCE) spectrum of PPy-TNTs increases in UV and visible light region. Moreover, The PPy-TNTs hybrids show much higher photoelectrochemical stability than the pure TNTs. © 2015 Elsevier Ltd. All rights reserved.

Xu J.,Jiaxing University | Bao J.-Q.,Jiaxing University | Yu M.-G.,Zhejiang University | Yu M.-G.,Hangzhou Environmental Group Company Ltd | Chen Y.-X.,Zhejiang University
Chinese Journal of Applied Ecology | Year: 2014

A research was done to study the Pb adsorption by the root cell wall of tea plant extracted from Longjing 43. It was indicated that the amount of Pb adsorbed by the root cell wall increased with augment of the initial pH of the solution under acidic condition, dramatically as the pH ranged from 2.0 to 4.5. The amount of Pb increased with the Pb concentration in the solution at pH 4.5, which could be well fitted by the Freundlich adsorption model. The adsorbed Pb reached 9.7 mg·g-1 under equilibrium condition, 90% of which was adsorbed in 320 minutes, while 50% was desorbed in 60 minutes based on the desorption dynamic curve. The kinetics of both adsorption and desorption could be well described by a second-order rate equation. The amount of absorbed Pb by the root cell wall varied after modified treatments, reducing by 51.1% after esterifing, 41.3% with pectinase, and 10.8% via aminomethylation, suggesting that carboxyl, galacturonic acid, pectin and amino, to some extent, all took part in the Pb adsorption by the root cell wall.

Duan D.-C.,Zhejiang University | Yu M.-G.,Zhejiang University | Yu M.-G.,Hangzhou Environmental Group Company Ltd | Shi J.-Y.,Zhejiang University
Chinese Journal of Applied Ecology | Year: 2014

Contamination of soils by lead (Pb) is of widespread occurrence because of the industrialization, urbanization, mining, and many other anthropogenic activities. It is urgent and necessary for scientists to uncover the mechanisms of uptake, translocation, accumulation and detoxification of Pb in plants for the following two reasons. First, it helps target and regulate the key process of Pb uptake by crops and vegetables and minimize the threat of Pb introduction to the food chain. Second, it helps cultivate Pb hyperaccumulating plants that can absorb and sequester excessive amounts from contaminated soils in their biomass without incurring damage to basic metabolic functions. The purpose of this review was to summarize the research advances in uptake, translocation and accumulation of Pb in plants and address the mechanisms by which plants or plant systems detoxify Pb. The further researches on the foliar uptake, the interactions between soil components and plant cell wall, as well as the integrated technologies for phytoremediation of Pb-contaminated soils were prospected.

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