| In this research, to discuss the alleviation role of lanthanum(La) and salicylic acid (SA) on Cd-stressed mazie seedlings, the SOD activity, MDA and ROS content were detected in mazie leaves, and the infrared spectrometry of mazie seedlings organizations were detected by Fourier transform infrared spectrometry(FTIR), then the corresponding changes of protein, nucleic acid and lipid could be determined.The results show that, after 48h of Cd stress, SOD activity, MDA and ROS content can be induced and increased in mazie seedlings. Appropriate concentration of SA and La can alleviate Cd stress at different levels and the content of ROS and MDA are lower. With Hoagland Applied in tank farming in 48h, 60mg·L-1 La and 20mg·L-1 SA were the most significant on alleviating Cd stress, In addition, the experiment also show that different concentrations of La were more significantly in 24h; after 24h, the ROS and MDA significant increased. in 48h, Appropriate concentration of SA still had the ability to alleviate Cd stress, but the high concentrations can lead to raise the content of ROS and MDA beyond Cd treatment, and these might exacerbate Cd stress.The La and SA were used to alleviate Cd stress and the IR of all samples were analyzed. The results show that:When Cd stressed mazie seedlings, the protein metabolism gradually reduced, and the Turn and a-Helix metabolism of protein secondary structure are more vulnerable by Cd. The nucleic acid metabolism increased in the early Cd treatment. However, in the continuing stress of Cd, the nucleic acid metabolism was inhibited. Lipid metabolism has been the impact of Cd toxicity. Through 20mg·L-1～100mg·L-1 La alleviate Cd stress, it suggested that 20mg·L-1～60mg·L-1 La could impact protein metabolism, With the increased concentration of La, the metabolism of protein secondary structure was more significantly changed. Under 20mg·L-1 and 100mg·L-1 La, the nucleic acid metabolism changed in volatility, however, under 60mg·L-1 La, the nucleic acid metabolism were stable, with the moment were similar to the control group. With different concentrations of La, the lipid metabolism were still inhibited by Cd toxicity and the lipid metabolism were similar to the Cd treatment group. Through 10mg·L-1～120mg·L-1 SA alleviate Cd stress, it suggested that a new protein produced, and the protein metabolism were more stable and similar to the control group on different concentrations of SA alleviation. At 48h, by 10mg·L-1 SA alleviation, the protein content suddenly increased and were significantly higher than the control group, then the metabolic of protein secondary structure changed, in particular the a-Helix and P-Sheet more significantly changed in 48h. In different concentrations SA alleviation early, the nucleic acid metabolism were not instability, however, with the increased concentration of SA, the nucleic acid metabolism were gradually similar to the control group at 48h. By low concentration SA, the lipid metabolism declined in 12h and increased after 24h, With the increased concentration of SA, the lipid metabolism were gradually similar to the control group.Through analysis of the IR spectrum fitting results by the rate of phosphor/amide II and lipids/amide II, the results showed that, La alleviation were similar to SA, and in low concentrations of La and SA alleviation, the rate of phosphor/amide II also fluctuant changed in the short term. This suggested that the nucleic acid metabolism did not recover the control level, and at 48h the fitting results indicated that, both La and SA did not alleviate Cd stress to the impact of proteins metabolic pathways, furthermore, in low concentration SA alleviating, Protein metabolism were more restrained. When La concentration is 100mg·L-1 and SA concentration is 120mg·L-1, the protein metabolism gradually restored to the control levels. With the concentration of La and SA gradually increased, the rate of lipids/amide II gradually restored to the control levels. This showed that the overall trend of lipid metabolism was similar to the protein metabolism by La and SA alleviating.In conclusion, it was suggested that FTIR was able to detect the chemical changes in Cd-stressed plants at early stages, and various spectral data can be used to analyze changes of various compounds in the plants. FTIR is more quick and convenient than other techniques of detecting physiological indicators. Due to a few amount sample needed, the entire process of plants growth can be determined with this method. Maybe the FTIR will be used extensively in the research on plants physiology due to its virtues of simple and efficient on manipulation. |
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