The Response Of Commelina Communis’ Growth To The Soil With Copper Polluted And Its Effect On The Copper Forms

Copper, the necessary micronutrient of plants, animals and human organ, is also the heavy metal of the environment. In order to figure out Commelina communis" physiological response to the added copper, influence to the soil environment and hyperaccumulation of copper, and to provide the scientific basis for recovering the contaminated soil, I had done the experiment of adding copper to soil and then planted Commelina communis. By observing the likelihood of Commelina communis, analyzing its nutrient contents and copper contents, and analyzing the copper forms of Commelina communis planted soil and no Commelina communis planted soil. The result presents that, the added copper affect the above-mentioned contents obviously.Experiment of direct photometric determination of soil available copper with sodium diethyldithiocarbamate in aqueous solution was conducted to explore a simple method to determine soil available copper. The results showed that the reaction of DDTC with Cu(II) can form a kind of stability yellow complex and can be direct determined by the spectrophotometry with the help of Arabic gum as solubilizing agent and ammonium citrate-EDTA as masking agent. The complex showed maximum absorbance at the wavelength of454, the apparent molar absorption coefficient ε was1.02×104L·mol-1·cm-1while the Beer’s law is obeyed by copper content in the range of0-4ug·mL-1, and the linear related coefficient, detection, average recovery rate and RSD wad0.9996,1.055μg·L"107.56%and5.75%, respectively. Having no significant difference at available copper content and RSD with inductively coupled plasma optical emission spectrometry (ICP-OES), this method was used to determine available copper in soil samples incubated by copper additions and the results showed soil available copper was linear significantly correlated with copper additions in soil. In summary, with simple operation, easy to get the necessary reagents, no need of expensive instruments, and the satisfactory exactitude and accuracy for determination of soil available copper, this method was cheap and worth to popularize in determining soil available copper.The pot experiment presents that, the copper concentration rang which Commelina communis can survival is from0to500mg/kg. The Commelina communis can grow normally is from0to100mg/kg. When copper concentration is higher than1000mg/kg, the Commelina communis can’t survive. Low copper concentration is good for the growth, for example the growth rate of Commelina communis in50mg/kg copper concentration soil is the largest. As the concentration of copper increased, copper stress began to inhibit the growth of Commelina communis. Starting from100mg/kg. the biomass, plants’height and growth rate of reduced significantly. Different copper concentration shows the same trends that Commelina communis’underground biomass is larger than aboveground biomass. Copper affect the aboveground biomass mainly. During0～100mg/kg copper concentration, the D-value range of underground biomass and aboveground biomass is22.47-36.78g, but200～500mg/kg copper concentration is0.38-0.78g.Commelina communis’growth would reduce the PH of soil, as the increasing acidity the soil’s pH lowed from5.6to4.4. The low pH may cause the death of Commelina communis.. The soil’s alkaline hydrolysis N、available P、available K and OM, vary opposite to the Commelina communis’ biomass as the copper concentration. While heavy copper contaminated soil’s CEC is higher.There existed correlation between the content of Commelina communis’s nitrogen, phosphorus and potassium and the alkaline soluble N, available P, available K concentrations of soil. The nutrients are mainly from soil, and the soil’sN、P、K content can satisfy the nutrition demand of Commelina communis’s growth. But the N、P、K content and its distribution in the stem, leaf and root of Commelina communis present different trends along with the change of soil copper concentrations, low copper concentration, the copper content of cauline leaf and root increases with the growth of exogenous copper’s concentration, And the root’s N content is higher than the cauline leaf. But it is opposite in high copper concentration. Copper stress to some extent can promote the Commelina communis absorb the nitrogen and phosphorus, but high copper concentrations is not conducive for the transmission of nitrogen and phosphorus. The copper stress has litter influence on the absorption of K. Iron is the essential micronutrients for animals and plants, the iron content of cauline leaf and root increases with the growth of exogenous copper’s concentration. Many studies have also shown that copper stress will increases the absorption of iron, and cause the decline in chlorophyll content.The soil’s N、P、K content can satisfy the nutrition demand of Commelina communis’ growth.the N、P、K content and its distribution in the stem, leaf and root of Commelina communis present different trends along with the change of soil copper concentrations, low copper concentration, the copper content of cauline leaf and root increases with the growth of exogenous copper’s concentration. And the root’s N content is higher than the cauline leaf. But it is opposite in high copper concentration. Copper stress to some extent can promote the Commelina communis absorb the nitrogen and phosphorus, but high copper concentrations is not conducive for the transmission of nitrogen and phosphorus. The copper stress has litter influence on the absorption of K. Iron is the essential micronutrients for animals and plants, the iron content of cauline leaf and root increases with the growth of exogenous copper’s concentration. Many studies have also shown that copper stress will increases the absorption of iron, and cause the decline in chlorophyll content.As the growth of exogenous copper’s concentration, the total copper content in the soil with Commelina communis planted is less than the no Commelina communis planted soil, it illustrats that Commelina communis can reduce the copper content in soil. Based on the improved BCR three-step extraction, the soil copper forms can be divided into weak acid soluble, reducible,oxidizable and residual. Without exogenous copper soil, the content of all forms presents a sequence of weak acid soluble> residual>reducible> oxidizable, Commelina communis planting, the sequence is residual>weak acid soluble> reducible> oxidizable.In addition, different exogenous copper concentration has different distribution, low exogenous copper concentration is mainly residual copper., less damaging; high exogenous copper concentration is mainly weak acid soluble copper and uneven distribution, associated with the transformation of exogenous copper in the soil. The weak acid soluble copper content increases with the growth of exogenous copper concentration, present the same trends along with the pH. Commelina communis can promote the transformation of reducible copper and reduce its proportion in the total copper. The content and distribution of oxidizable copper in the soil with Commelina communis planted has taken on a strong positive connection with the soil organic matter, and negative connection with the soil pH. The residual copper is fixed in the soil. Its distribution decreases with the growth of exogenous copper concentration, and the pant of Commelina communis can promote the transformation of oxidizable copper to others. Weak acid soluble copper is important to available copper, and the available copper content has a significant linear correlation with the total copper content, and mainly from residual and reducible copper. Commelina communis planting can reduce copper ratio effectively.