RESUMO
Aluminum (Al) toxicity is one of the major constraints to crop production in acid soils. In order to provide a correct and effective identification method of aluminum toxicity of soybean in red soil regions, Fourier transform infrared spectroscopy (FTIR), thermogravimetry (TG) and differential thermal (DT) analysis were adopted to study the soybean root under different Al treatments. The results showed that the aluminum contents of soybean roots treated with 60 and 90 mg x L(-1) Al concentration were higher than that with other aluminum treatment, and the Al content reached significant aluminum toxicity level. In the same wavenumber range, the character, wavenumber and absorption peak of infrared spectra were different from those under different Al treatments. In summary, the absorption peaks at 3300, 2 930, 1542 and 721 cm(-1) were the characteristic peaks for identification that can be used to evaluate the Al toxicity of soybean. Detailed description is as follows: with the high aluminum treatment (60 and 90 mg x L(-1)), the characteristic peaks at 3300 and 2930 cm(-1) were higher than those with other aluminum treatment. There are no infrared bands at 1542 cm(-1) under 90 mg x L(-1) aluminum treatment, as the characteristic peak of Amide II. However, the characteristic peak at 721 cm(-1) was clearly shown at 60 and 90 mg x L(-1), but no sign was shown in 0, 10 and 30 mg x L(-1) aluminum concentration. Curves of TG and DT revealed the greatest difference with different Al treatment in the range of temperature of 400-500 degrees C. Under the Al treatment above 30 mg x L(-1), TG curve had less weight than that at 0 mg x L(-1), which indicated that the root system may be more lignified, producing some material hard to be burned. DT curve had double peaks at 60 and 90 mg x L(-1) Al treatments, which may also be used as identification mark of Al toxicity. Because some features were expressed under Al treatment with FTIR, TG and DT, the technology of FTIR, TG and DT provided a new way to identify Al toxicity of soybean in red soil region.
