玉米幼苗根际土壤微生物活性对芘污染的响应

用根际袋法土培试验研究了玉米幼苗根际与非根际土壤微生物量碳、微生物熵、代谢熵和土壤酶活性对不同芘污染水平(50、200、800mg·kg-1,记为T1、T2、T3)的响应差异。结果表明,较低浓度芘可适当的刺激玉米幼苗的生长,而较高浓度芘则抑制幼苗生长,其抑制作用随芘处理浓度的提高而增强;芘对玉米根系的影响要大于对茎叶的影响。玉米幼苗能够明显促进土壤中芘的去除。根际和非根际土壤中芘的去除率分别为56.67%-76.18%和32.64%-70.44%,根际土壤中芘的平均去除率比非根际土壤高16.06%。同处理中根际土壤芘含量显著低于非根际土壤,随着芘处理浓度的提高其差异更加显著。根际土壤微生物量碳、微生物熵、多酚氧化酶活性、脱氢酶活性和磷酸酶活性均高于非根际土壤,代谢熵低于非根际土壤,且其差异随芘处理浓度的提高而增大。在不同芘污染水平下,微生物量碳、微生物熵和脱氢酶活性根际和非根际土壤为T1T2T3,代谢熵为T3T2T1;多酚氧化酶活性根际土壤为T2T1T3,非根际土壤为T1T2T3;磷酸酶活性根际土壤为T3T1T2,非根际土壤为T1T2T3。土壤中残余芘含量与土壤微生物量碳、微生物熵、多酚氧化酶、脱氢酶和磷酸酶活性呈显著负相关,与代谢熵呈显著正相关。

Response of microbial activity in the rhizosphere of maize seedlings (Zea mays L.) to pyrene contamination

A soil-cultivating test, with rhizobag technique, was used to quantify the responses of microbial biomass carbon and quotient, metabolic quotient, and soil enzyme activity in rhizosphere and non-rhizosphere soil under three concentration levels of pyrene (50, 200, and 800 mg?kg-1, denoted by T1, T2, and T3, respectively) after 45 days phytoremediation by maize seedlings (Zea mays L.). The growth of maize seedlings was slightly stimulated at lower pyrene concentration, while inhibited at higher pyrene concentration, and the effect increased with initial pyrene concentration. In addition, the effect of pyrene on maize root was more obvious than that on shoot. Maize seedlings significantly promoted pyrene dissipation in the soil. During the experimental period, 56.67%-76.18% and 32.64%-70.44% of spiked pyrene disappeared from the rhizosphere and non-rhizosphere soils respectively. The average removal rate of pyrene in rhizosphere soils was 16.06% higher than that in non-rhizoshpere soils. In the same treatment, the concentration of pyrene in rhizosphere was significantly lower than that in non-rhizosphere, but the removal rate was on the contrary, and their differences were positively affected by increasing initial pyrene concentration in soil. The microbial biomass carbon and quotient, polyphenol oxidase, dehydrogenase, and phosphatase activities were higher in rhizosphere than those in non-rhizosphere. The metabolic quotients were lower in rhizosphere than that in non-rhizosphere and the corresponding differences increased with increasing pyrene concentration in soil. Under different concentrations of pyrene, the microbial biomass carbons and quotients and dehydrogenase activities in rhizosphere and non-rhizosphere were T1>T2>T3, while the metabolic quotients were T3>T2>T1. The polyphenol oxidase activities were T2>T1>T3 and T1>T2>T3 in rhizosphere and non-rhizosphere, respectively. The phosphatase activities were T3>T1>T2 and T1>T2>T3 in rhizosphere and non-rhizosphere, respectively. Significantly negative correlations were found between pyrene concentrations and the soil microbial biomass carbon and quotient, polyphenol oxidase, dehydrogenase, and phosphatase activity. There were significantly positive correlations between pyrene concentrations and the metabolic quotient.