Effects Of Mn, Cd Stress On Physiological And Biochemical Characteirstics Associated With Rhizospheric Enzyme Activity Of Two Aquatic Plants

Heavy metal pollution is one of the most important global environmental pollutions,because of its strong toxicity, difficult degradation. Absorption and accumulation of heavymetals in aquatic plants, can induce metabolic abnormality of plants, and even death,seriously affect the health of aquatic ecosystems. In this study, using the common aquaticplants-Elodea nuttallii and Oenanthe javanica, as research material, we discussed effects ofMn2+, Cd2+stress on the aquatic plants chlorophyll, soluble protein, ROS, antioxidantenzymes, and rhizosphere enzymes. Following are the results:1.Compared with control group (CK), low concentration Mn2+had the promoting effectson Chl and soluble protein contents in Elodea nuttallii and Oenanthe javanica, while highconcentration Mn2+had stimulation on them in short time, then showed inhibition, or showedinhibition all the time. In short time, the low concentration Cd2+had stimulated effects. UnderMn2+and Cd2+combined stress, under low concentration of combined stress, Mn2+might playa role in alleviating the poisonousness of Cd2+; but Mn2+had a strengthened effects underhigh concentration of combined stress. In contrast, under heavy metal stress, Oenanthejavanica was more resistant to stress than Elodea nuttallii; and soluble protein was moresensitive than Chl.2.Compared with CK, low concentration Mn2+had the inhibiting effect on MDA in shorttime, and stimulated firstly and then inhibited H2O2, O2·—,while had stimulation on SOD,POD, CAT. Under high concentration Mn2+, MDA, H2O2, O2·—and SOD, POD continue toincrease, CAT in Elodea nuttallii also increased, but CAT in Oenanthe javanica increasedfirstly and then decreased. Under low concentration Cd2+, MDA continued to increase, O2·—increased firstly and then decreased, H2O2in Elodea nuttallii increased, but H2O2in Oenanthejavanica increased firstly and then decreased; SOD, POD, CAT increased. Under highconcentration Cd2+, MDA, H2O2, O2·—increased and SOD, POD, CAT all increased firstlyand then decreased. Under Mn2+and Cd2+combined stress, high concentration Mn2+accelerated the inhibition of Cd2+on SOD, POD, CAT. Compared with Elodea nuttallii, thesingle and combined stress of Mn2+, Cd2+on Oenanthe javanica are lighter, especially forMn2+stress. Under the single and combined stress of low concentration Mn2+, Cd2+, SOD,POD, CAT all increased in order to alleviate the oxidative stress to aquatic plants together,while Under the single and combined stress of high concentration Mn2+, Cd2+, SODperformed the main protection.3.Compared with CK, low concentration Mn2+had the promoting effects on rhizosphereenzymes in Elodea nuttallii and Oenanthe javanica, rhizosphere enzymes activities wereinhibited under high concentration of Mn2+. Under Cd2+stress, enzymes activities changedsimilarly with Mn2+stress, rhizosphere enzymes activities in Elodea nuttallii decreased asfollows: Urease>APA>DHA, and those in Oenanthe javanica as: DHA>Urease>APA. UnderMn2+and Cd2+combined stress, under low concentration, rhizosphere enzymes activities werelower than Mn2+stress, and higher than Cd2+stress; under high concentration, rhizosphereenzymes activities were lower than single stress, it showed that low concentration Mn2+has alleviation to Cd2+stress, and high concentration Mn2+and Cd2+showed synergistic effect.In this paper, we studied the effects of different concentrations of Mn2+, Cd2+andcombined stress on Elodea nuttallii and Oenanthe javanica, in order to provide the theoryreference for the water environment restoration work of Elodea nuttallii and Oenanthejavanica, and help to carry out water restoration with aquatic plants scientifically.