[Comparison of the methods for extracting and purifying microbial total DNA from an aeolian sandy soil].

In order to select and establish an appropriate method for extracting and purifying the microbial total DNA from an aeolian sandy soil, six extraction methods (five direct methods and one indirect method) and two purification methods were examined, with the quantity and quality of extracted and purified total DNA compared. All the six extraction methods could extract the total DNA with a length of approximately 23 kb, among which, the improved SDS high salt extraction method (using 40% PEG8000 and 4 mol x L(-1) NaCl to precipitate DNA) was the best. This method could have a yield slightly less than that obtained by using kits, and the extracted DNA had the highest purity after purification, being available in 16S rDNA PCR amplification. Among the purification methods, the effect of agarose gel electrophoresis plus minicolumn was satisfactory, with most of the purified total DNA being able to be PCR-amplified and meet the requirements of the purity of DNA in the follow-up molecular operations.

[Determination of nutrient elements in transgenic insect-resistant cotton tissues by three different spectroscopical methods].

In order to find out the effects of exogenous genes, such as Bt and Bt coupled with CpTI, on nutrition metabolism in transgenic plants, totally eleven types of nutrient elements in transgenic Bt (Z30) and Bt-CpTI (CCRI41 and SGK321) cotton were determined using methods of flame atomic absorption spectroscopy, flame atomic emission spectroscopy and spectrophotometry at flowering stage and boll-opening stage. The results showed that the chemical composition of plant nutrition in transgenic insect-resistant cotton differed in comparison with non-transgenic cotton counterparts related to varieties, tissues and stages. The content of total N in transgenic cotton changed most significantly. Especially, it increased by 21% for transgenic Bt cotton Z30 compared to non-transgenic cotton Z16. These changes in total N content were probably caused by both transgenes expression in transgenic cotton and other processes not studied in this experiment. The content of Mg, Na and Cu in transgenic cotton varied significantly only in some certain varieties or tissues. It was unobvious how the incorporation of transgenes impacted on the content of organic C, total P, total S, K, Ca, Fe and Zn in transgenic cotton. The authors speculated that there were no significant changes in utilization and accumulation of these nutrient elements between transgenic insect-resistant cotton and their non-transgenic cotton counterparts (Z16, CCRI23 and SY321, respectively).

[Amelioration effect of sand-fixing Hedysarum fruticosum plantations on soil nutrient contents and biological activities].

With adjacent semi-moving dune as the control, this paper studied the effects of 5-, 10- and 22-year old Hedysarum fruticosum plantations on the nutrient status, microbial biomass, and enzyme activities at the soil depths 0-10, 10-20 and 20-30 cm. The results showed that with the establishment of H. fruticosum plantation on moving dune, soil C, N, P and K contents and biological activities increased obviously with the increasing age of the plantation, and the increment was much higher at 0-10 cm than at 10-20 and 20-30 cm. At 0-30 cm, soil C/N increased from 7.3 to 8.5, and microbial biomass C, N and P as well as the activities of urease, protease, saccharase, phosphomonoesterase, dehydrogenase, polyphenol oxidase and nitrate reductase all increased. Among the test enzyme activities, saccharase activity had the most significant increase, with its value at 0-10 cm being 49.7-284.5 times of the control. There were significant positive correlations between soil microbial biomass C, N and P and organic C, total N and total P, respectively, and between soil microbial biomass and enzyme activities.