| With the extensive usage and discard of organic pesticides in industrial and agricultural, production have caused serious pollution to soil and water, resulting in heavy metal is one of the important sources of serious environmental pollution, and it has a higher damage for flora and fauna. After metal cadmium contaminate the crops, it directly affect the yield and quality. Cadmium can finally enter the body via the food chain, and gather in the human body endanger human health. Therefore, cadmium pollution has become a focus of environmental issues of global concern, environmental cadmium toxicity studies have been more widespread attention. The main results as follow:(1) Using the wild-type Arabidopsis Col-0as the experimental materials, the morphological changes of Arabidopsis roots were observed under several different concentrations of cadmium (0μM,25μM,50μM,75μM,100μM). The morphological changes of Arabidopsis roots, which is included the length of main root, meristematic zone and elongation zone, change of lateral roots and root hairs, is a classical physiological index for research of root development mechanism. The results showed that compared with the Arabidopsis root that is not applied with cadmium, the taproot length and meristem and elongation zone length were shorted, while the number of lateral roots and root hairs were increased and the length of root hairs also shorted after cadmium treatment. Simultaneously, following with increasing in concentration of cadmium, the morphological changes of Arabidopsis roots were more obvious.(2) Comprehensive the results of the first chapter with the expression of ethylene-related gene, we selected75μM cadmium chloride to do further research and added two ethylene insensitive mutants ein2-5and ein3-leill-1. Treated with75μM cadmium chloride stress, we could seen the taproot and meristem and elongation zone length of two ethylene mutants were higher than the wide-type under untreated with cadmium, but with the extension of the processing they were higher than two ethylene-insensitive mutants.(3) At the same time, the superoxide accumulation as well as progression of programmed cell death (PCD) mainly was detected in root meristematic and elongation zone. Meanwhile, these three indicators of the two ethylene mutants were higher than the wild type. The above results have confirmed ethylene plays an important role in superoxide accumulation and cell death of Arabidopsis roots.(4) In order to further confirm whether participated in the responses of Arabidopsis root system under cadmium stress, ethylene synthetic precursor ACC (0.1μM,1μM) and ethylene synthesis inhibitors AIB (50μM) were applied basing on75μM cadmium treatment. According to the results of NBI staining, it showed0.1μM ACC could reduce the accumulation of oxide in roots to a certain extent under cadmium stress, while high concentration of ACC and AIB could not relief the oxidized accumulation of Arabidopsis roots, but could promote the degree of oxidative injury. ACC that applied to three seedlings outside has improved the biological activity of three SOD isoenzymes under cadmium stress in wide-type, while not appeared in the two ethylene mutants. This also means that ethylene has an important significance in the activated expression of SOD enzyme under cadmium stress. Ethylene could reduce the accumulation of superoxide by promote SOD enzyme activity. Meanwhile, ethylene was also involved in root morphology, including root length, lateral root and root hair response to cadmium injury. In summary, ethylene plays an important role in response to Arabidopsis root system under the control of cadmium stress. |
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