Factors including Mg2+, dNTP and primer that affected RAPD were studied using orthogonal experimental design, and at the same time, anneal temperature, extending time and cycles were also studied. Finally, PCR reaction system that is feasible for black soil microbial PCR amplification was determined, containing 7 ng DNA template, 20 pM random primers , 1.5 U Taq DNA polymerase, 3.0 mM MgCl2 and 0.2 mmol·L-1 dNTP, with procedure: 40 cycles for 3 min at 94 ℃ (temperature), 40 s at 37℃ (annealing), 1.5 min at 72 ℃ (extension), a final elongation step at 72 ℃ for 7 min.
In order to study the effects of exogenous cinnamic acids on plant growth, contents of photosynthetic pigment, rootactivities and ATPase activities of root membrane at cucumber seedling stage, the seedlings of Shandong Mici cucumberwere tested. The results showed that seedlings growth, contents of photosynthetic pigment, root activities and ATPaseactivities of root membrane were inhibited by cinnamic acids. The growth and root activities of seedlings were significantly(P<0.05) lower in the soil amended with 100 mg kg-1 cinnamic acids compared to the control. The contents of chlorophylla, chlorophyll a+b and carotenoid of seedlings significantly (P<0.05) decreased in the soil amended with 200 mg kg-1cinnamic acids, whereas ATPase activities exhibited a higher sensitivity and greatly decreased in the soil amended with 50mg kg-1 cinnamic acids. These results suggested that cinnamic acids could induce a stress condition, and the stressintensities increased with enhanced cinnamic acid concentration.
