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In this work, the Co0.5Zn0.5Fe2O4 microtube was prepared via a template-assembled sol-gel method, where three kinds of natural fiber worked as template. Effect of template types on morphology, specific area, and magnetic properties under different temperatures of ferrites microtube was investigated. XRD results confirm the formation of pure spinel Co0.5Zn0.5Fe2O4; SEM results proves that the CZF-microtubes is mono-dispersed and exactly copies the morphology of the corresponding template. It possesses excellent magnetic properties (Ms, 62.62 emu g−1) and higher specific area (51.11 m2 g−1), respectively, the former is mainly due to the net-liked microstructure and distribution of higher magnetic magneton cation in crystal cell, and the latter is attributed to not only the smaller grain size, but also the stack manner of nanoparticles. Below Curie temperature, coercivity of CZF-microtubes decreases with an increased temperatures in accordance with the ferromagnetism theory as the degree of atomic thermal vibration increases; Above Curie temperature, the unique variety of coercivity is attributable to not only the competition between the 2nd and 4th order crystal field terms derived from the d electrons of Fe3+ and Co2+ in crystal cell, but also the easy magnetized direction switches from basal plane to c axis via a preferred orientation of the magnetic moments in microtubes structure; The high Hc value of CZF-microtube above Blocking temperature TB (450.19 K) results from the existence of interparticle interaction as nanoparticles of it aggregate to produce a microtube structure, and resulting in a deviation from normal Kneller's law. [ABSTRACT FROM AUTHOR]

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Phytolacca americana L. has the capacity to take up and accumulate to very high levels heavy metals such as Mn and Cd, and is used for phytoextraction of heavy metal contaminated soils. The role of antioxidative enzyme of Phytolacca americana in response to Cd stress is unknown. The 6-week-old seedlings of Phytolacca americana were exposed to half strength Hoagland solution with 200 micromol/L CdCl2 or 400 micromol/L CdCl2 for 4 days. The content of H2O2 and MDA, and electrolyte leakage increased, while the photosynthetic rate decreased, indicated that the oxidative damage induced by Cd stress in Phytolacca americana was one of the metal toxicity mechanism. The activities of SOD and POD increased rapidly with elevated Cd concentration and exposure time, CAT activity was stable in response to 200 micromol/L CdCl2 stress, and increased only at 3 d later upon 400 micromol/L CdCl2, treatment. Suggested that the enzymatic antioxidation capacity played important role in Cd tolerance of hyperaccumulator plant.

Plant species capable of accumulating heavy metals are of considerable interest for phytoremediation and phytomining. The mechanism of Mn tolerance/hyperaccumulate in Phytolacca americana L. is less known. To elucidate the role of antioxidative enzyme in response to Mn, the 6-week-old seedling of Mn hyperaccumulator P. americana and non-accumulator-tobacco (Nicotiana tabacum) were exposed to half strength Hoagland solution with 1 mmol x L(-1) or 3 mmol x L(-1) MnCl2 for 4 days. The photosynthetic rate in P. americana decreased more slowly than that in tobacco, while the MDA content and electrolyte leakage in tobacco increased more rapidly than that in P. americana. For example, after exposure to 1 mmol x L(-1) Mn for 4 days, the photosynthetic rates of P. americana and tobacco in comparison to the control reduced by 13.3% and 75.5%, respectively. The MDA content and electrolyte leakage in tobacco increased by 347.3% and 120.1%, respectively, whereas Mn had no marked effect on both of it in P. americana, indicated that the oxidative damage in tobacco was more serious than that in P. americana. The activities of SOD and POD of both species increased rapidly with elevated Mn concentration and exposure time in both species, the increase of SOD activity in P. americana was higher than that in tobacco. CAT activity in tobacco declined rapidly, while the activity of CAT in P. americana was increased. The activities of SOD, POD and CAT in P. americana upon 1 mmol x L(-1) Mn exposure increased by 161.1%, 111.3% and 17.5%, respectively. The activities of SOD and POD in tobacco increased by 55.5% and 206.0%, respectively, while CAT activity decreased by 15.6%, indicating that the antioxidative enzymes in P. americana, particularly in CAT,could fully scavenge the reactive oxygen species generated by Mn toxicity. These results collectively indicate that the enzymatic antioxidation capacity is one of the important mechanisms responsible for Mn tolerance in hyperaccumulator plant species.