Physiological Response Of Konjac To Selenium And The Selenium Determination By Ultraviolet Spectrophotometry

Selenium is a very important trace element to human and animal bodies, Selenium disorder in environment is harmful to human and animal health, but the necessity of selenium for plants have not been identified. The investigation of the physiological response of plants to selenium has important significance in theory and practice to reveal the relationship between selenium and plants, regulate the selenium contents of plants and improve selenium nutrient condition in human beings and animals.In order to understand the effect of selenium on plants, seed and soil, the field samplings, soil pot experiments and incubation experiments were conducted, in which the selenium and nutrient element content and antoxidation of konjac in soil pot experiment were determined and the effect of selenium addition on seeds germination and soil enzyme activities in incubation experiment was analyzed. The result indicated that the selenium content and enriching ability of konjac was controlled by the soil selenium application levels, and soil selenium application influenced on biomass and nutrient content of konjac, foliar selenium application affected the oxidation resistance of konjac and external selenium additions impacted the germinations of some seeds and the activities of some soil enzymes.The measurement of field sampling showed that selenium content in konjac which was significant higher in leaves than in corm varied with the sampling spot and was significantly and linearly correlative to soil selenium contents. Results from soil pot experiment with selenium applications in the range of0-50mg kg-1indicated that, with significant higher in fluvo-aquci soil and in leaves than in red soil and in corm, the selenium content in konjac was significantly and linearly correlative to soil selenium application. The bioaccumulation factor of konjac on soil selenium was higher in stems and leaves than in corms, higher in fluvo-aquci soil than in red soil, and higher in selenium applied soil than in natural soil, and these showed that selenium availability was higher in fluvo-aquci soil than in red soil and higher in selenium applied soil than in natural soil. In soil selenium application, the selenium accumulation in konjac and the utilization ratio of konjac to soil selenium application was higher in corms and in fluvo-aquci soil than in leaves and in red soil, respectively, so the selenium enriching ability of konjac was higher in corms and in fluvo-aquci soil than that in leaves and in red soil. These testified that selenium accumulation and the utilization ratio of konjac to soil selenium was more suitable to evaluate the enriching ability of konjac to soil selenium.The konjac biomass was not impacted by selenium below10mg kg-1application level, but at50mg kg-1, the leaves, corms and total biomass, fresh weight of konjac corm and the ratio of seed fresh weight to corm fresh weight decreased significantly, and this meant that higher soil selenium level suppressed the growth of konjac. Lower konjac biomass in fluvo-aquci soil than that in red soil and higher reduce rate of konjac biomass in fluvo-aquci soil than that of red soil demonstrated that the suppression of high selenium level on konjac growth depended on soil environment and this reason is that the toxicity of hexavalent selenium in fluvo-acquci soil which was alkaline was higher than that of tetravalent selenium in red soil which was acidic. Effect of soil selenium applications on nutrient element contents in corms varied with type of elements and soils. The high level of selenium (50mg kg-1) increased N content in konjac corm in fluvo-aquci soil significantly, but did not effect N content in corms in red soil. Both in fluvo-aquci soil and in red soil, high soil selenium application decreased P and K content in konjac corms significantly, while the decreasing degree was higher in fluvo-aquci soil than that of in red soil. Soil selenium applications altered the proportion of N, P and K in konjac corms, and the high level of soil selenium application increased the value of N/P, N/K and K/P. This implied that the high selenium application accelerated nitrogen assimilation of konjac, but decreased assimilation of konjac to P and K.A pot experiment of foliar selenium application indicated that selenium had effects on enzyme activities of GSH-Px, CAT and POD and MDA content. Ten days after spraying selenium, the activity of GSH-Px and CAT increased164.9%and26.0%, but the activity of the POD and the content of MDA decreased34.3%and13.4%in leaves of konjac, respectively. These indexes had something to do with the oxidation resistance of plants, thus, the proper foliar selenium application can prevent oxidation damage of plant cells and improve the oxidation resistance of plants.Selenium in soil and plants was determined at the ultraviolet wavelength of330nm using o-phenylenediamine, n-hexane and phosphate, oxalate and oxammonium hydrochloride as chromogenic regent, extracting regent and masking reagents to interferences, respectively. Without expensive instruments and special reagents, this method is cheap and practicable and can meet the certain sensitivity demand.