| With the development of modern industry, the influence of heavy metal pollution to human life is becoming bigger and bigger. Heavy metal pollution of soil seriously interfere with plant growth, even could cause the vegetation degradation. More dangerous is that under the enrichment of the food chain, those heavy metal that has entered the plant will be uptaken by the animals and microbial for food, and finally the heavy metal will be get into human body. Hence, it is a danger to human health.Isoetes sinensis Palmer is a kind of ancient clubmosses plants that belongs to Isoetes genus, and also is the earliest discovered plant of Isoetes genus. It possesses high research value in the system evolution because of its special ancient origin and evolution. However, due to its own survival characteristics and the influence of human activities, Isoetes sinensis is in the state of critically endangered at present, so it is listed as a national level and endangered plants.Previous studies have found that Isoetes sinensis possess significant strong tolerability and high absorbance capacity. In order to further research the effects of other heavy metal on Isoetes sinensis, in this study three kinds of heavy metallic salts(Cd Cl2, Hg Cl2, K2Cr2O7) that can cause serious environmentally pollution were chosen to stress treatment for Isoetes sinensis. Set concentration based on the " Soil Environmental Quality Standards PRC"(GB15618-1995). The contents of three heavy metal in each part of the treated plant, the activity of leaf antioxidant enzymes and the expression quantity of seven differential express genes were determined, these lay the foundation of researching Isoetes sinensis whose endangered mechanism and resistance mechanism of heavy metal.The results were as follows: 1) The heavy metal including Cd, Hg and Cr could get into the plant body through the root and leaves of Isoetes sinensis, the heavy metal that entered the root could transport up to the leaves and tubers. 2) The absorbance of Isoetes sinensis for heavy metal including Cd, Hg and Cr were strong. After training ten days in the Cd Cl2 solution with concentration of 1 mg/L and Hg Cl2 solution with concentration of 1.5 mg/L, the contents of Cd and Hg in the leaves that were directly contacted to contaminating fluid reached 255.20 mg/kg(dry weight) and 120.12 mg/kg(dry weight). However, the content of Cr in the leaves that were dealt with Cr solution with the concentration of 400 mg/L reached up to 22155.98 mg/kg(dry weight), which was slightly higher than the content of root with the same processing method. The growth situation of plants had no obvious changes under the stress of Cd and Hg, but the growth of plants were serious inhibition under the stress of Cr. 3) The activities of three antioxidant enzymes increased under the stress of Cd and Hg in Isoetes sinensis, which played an important role in improving the resistibility to heavy metal for Isoetes sinensis. However, the activities of antioxidant enzymes present the downward trend under the stress of Cr in Isoetes sinensis, the reason analyzed was resulted from the concentration of Cr treatment was higher than the threshold of the antioxidant enzymes in Isoetes sinensis. 4) After the analysis of the seven differential express genes previously isolated from Isoetes sinensis, it was found that the expression quantity of TDF9, TDF10, TDF11 and TDF12 were very weak under the normal condition. However, the expression of target gene escalated with the stress of heavy metal, when the duress time to 72 h the expression began to decline. TDF1, TDF2 and TDF3 possessed strong expression in front of the stress, rapidly dropped after the start of expression, and then gradually increased. The expression of the above seven differential express genes were influenced by the stress of heavy metal, the results provided research foundation of further studying the molecular mechanism of heavy metal stress in Isoetes sinensis. |
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