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Many plant species excrete organic acids into the rhizosphere in response to aluminum stress to protect sensitive cells from aluminum rhizotoxicity. When the roots of Eucalyptus camaldulensis, a major source of pulp production, were incubated in aluminum-toxic medium, citrate released into the solution increased as a function of time. Citrate excretion was inducible by aluminum, but not by copper or sodium chloride stresses. This indicated that citrate is the major responsive organic acid released from the roots of this plant species to protect the root tips from aluminum damage. Four genes highly homologs to known citrate-transporting multidrugs and toxic compounds exclusion proteins, named EcMATE1-4, were isolated using polymerase chain reaction-based cloning techniques. Their predicted proteins included 12 membrane spanning domains, a common structural feature of citrate-transporting MATE proteins, and consisted of 502-579 amino acids with >60 % homology to orthologous genes in other plant species. One of the homologs, designated EcMATE1, was expressed in the roots more abundantly than in the shoots and in response to both Al and low pH stresses. Ectopic expression of EcMATE1 and 3 in tobacco hairy roots enhanced Al-responsive citrate excretion. Pharmacological characterization indicated that Al-responsive citrate excretion involved a protein phosphorylation/dephosphorylation process. These results indicate that citrate excretion through citrate-transporting multidrugs and toxic compounds exclusion proteins is one of the important aluminum-tolerance mechanisms in Eucalyptus camaldulensis.

A series of Ni-based catalysts were prepared using hydrogen reduction of Ni/Al hydrotalcite-like compounds (Ni/Al HTlcs) synthesized by coprecipitation. The physico-chemical properties of Ni/Al hydrotalcite-like compounds and the corresponding Ni-based catalysts were characterized using inductively coupled plasma (ICP), BET surface areas, X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) techniques. The results indicated that Ni/Al HTlcs with layered structures could be successfully prepared by the coprecipitation method, and the characteristic HTlcs reflections were also observed in the XRD analysis. The NiO and Ni0 phases were identified in all Ni-based catalysts, which displayed randomly interconnected pores and no layer structures. In addition, the studies also found the Ni/Al HTlcs and Ni-based catalysts had high specific surface areas, low pore volumes and low pore diameters. The catalytic hydrogenation of ethyl acetate to ethanol with Ni-based catalysts was also investigated. Among the studied catalysts, RE1NASH-110-3 showed the highest selectivity and yield of ethyl acetate to ethanol, which were 68.2% and 61.7%, respectively. At the same time, a major by-product, butyl acetate, was formed due to an ester-exchange reaction. A proposed hydrogenation pathway for ethyl acetate over Ni-based catalysts was suggested.