Effects Of Cu And Cr On Physiological And Biochemical Characteristics Of Wheat And Soil Enzyme Activities

Heavy metal toxicology research is one of the important contents of research area on ecological environment Toxicology. Combined pollution has drawn extensive attention of scholars both at home and abroad and has become an important development direction of environment science. As one of the necessary trace elements to plant life activities, copper(Cu) is involved in varieties of metabolic reactions during the process of plant growth and development, however, when there are too much Cu in the soil or in plant itself , it would be a environmental problem.Chromium(Cr) is one of the main heavy metal elements that can pollute the environment, and it has direct and potential hazards to human and animals by entering the body through being absorbed by the plant and the food chain. The paper selected Cu and Cr as object, effects of Cu and Cr on physiological and biochemical characteristics of wheat and soil enzyme activities were studied, the author aimed not only to provide basis for crop protection, but also to provide basis for soil heavy metal contamination and prevention and cure. Specifically, this paper focuses on the following three aspects:(1) In 1/4Hoagland hydroponic solution culture experiment, the photosynthesis and chlorophyll content of wheat seedling leaves under single element and compound stress of copper(Cu) and chromium(Cr) were studied, the results showed that the photosynthesis characteristics of the chosen wheat were impacted by Cu and Cr, Under single copper stress, the photosynthetic rate and chlorophyll content rised at low copper concentrations and reduced at high concentrations; Under single chromium stress, the net photosynthetic rate and chlorophyll content declined with the increasing of chromium concentration;Under combined stress, the photosynthetic rate increased at low concentration and reduced at high concentration; the chlorophyll content declined with the increasing of combined concentration; the reason of the photosynthesis rate changing for this experiment was non-stomata factor and the trend of chlorophyll content was similar to net photosynthesis rate, it indicated that Cu and Cr impact photosynthesis indirectly through chlorophyll content.(2) In 1/4Hoagland hydroponic solution with Cu and Cr culture experiment, the effect on wheat germination rate and membrane lipid peroxidation by adding exogenous Ca2+ and copper and chromium combined stress was studied, and effects on the activities of three main enzyme of the antioxidant enzyme system such as superoxide dismutase(SOD), catalase(CAT), peroxidase(POD) were analyzed, results showed that the existence of Cu and Cr reduced the germination rate of wheat; After adding Ca2+,the germination rate first increased and then decreased with the Ca2+ concentration, when the Ca2+ concentration is 10mg/L, the germination rate was 78.67%, but to the highest concentration of 100mg/L, the germination rate of wheat dropped to 34.67%; Cu and Cr caused membrane lipid peroxidation to wheat seedlings cells so that SOD, CAT activities declined while POD activity increased, MDA content show increased; plusing a low concentration of Ca2+ can alleviate the membrane lipid peroxidation, but over a certain range, membrane lipid peroxidation will still occur(3) Effects of different concentrations of two heavy metals(Cu and Cr) applied to brown soil and alluvial soil on urease activity, sucrase activity and catalase activity were studied. The results showed that during the treatment of 40 days Cu and Cr had a remarkable inhibition effect on soil urease activity and catalase activity in both soil and the sucrase in brown soil was activated while it's inhibited in alluvial soil; the inhibition rate increased and the activation rate decreased with the increase of the concentrations of Cu and Cr in brown soil while the inhibition rate increased with the increase of the concentrations of Cu and Cr in alluvial soil; in both soil, urease and catalase were more sensitive than sucrase to Cu and Cr combined stress. The SOD and CAT activities increased while POD activity and MDA content decreased below the concentration of 50mg/L, and membrane lipid peroxidation was alleviated, when the Ca2+ concentration to 100mg/L, SOD, CAT, POD activities dropped and MDA content increased to the maximum, the high concentration of Ca2+ being another stress with heavy metal exacerbated the extent of membrane damage.