草坪土壤的N2O产生途径及其对施氮肥的响应

 硝化作用、反硝化作用和硝化细菌反硝化作用是土壤中产生N₂O的主要途径。以常用的冷季型草坪草早熟禾为对象，采用气体抑制剂培养法研究了不同施氮量对草坪土壤N₂O排放及其产生途径的影响。结果表明，对照草坪土壤的N₂O日排放量为7.2 ~ 8.2 g · m^-2 · d^-1，年施氮量10 g · m^-2未改变草坪土壤N₂O排放强度，年施氮量25、35 g · m^-2处理则分别比对照增加1.52倍和1.88倍，但二者之间没有显著差异。对照草坪土壤N₂O产生途径主要以异养硝化作用为主，其贡献率达65.7%，反硝化作用贡献率为34%，自养硝化和硝化细菌反硝化过程几乎不发生。年施氮量25 g · m^-2时，N₂O排放以硝化细菌反硝化、异养硝化和反硝化途径为主，贡献率分别为35%、35%和29%。年施氮量35 g · m^-2时，N₂O排放来自于4个途径，其中反硝化途径占41%，自养硝化途径贡献率增加至20%。

Host Reaction and Sequence Analysis of Coat Protein Gene of Cucumber mosaic virus Isolates Infecting Hami Melon in Xinjiang

The samples of Hami melon with virus-infected symptoms were collected from naturally infected plants growing in sixteen of the major melon-growing locations in Xinjiang. RT-PCR was used to detect Cucumber mosaic virus（CMV）in the samples. Seventeen CMV isolates were obtained from 12 major melon-growing locations by repeated single-local-lesion transfers in Vicia faba. Host reaction and sequence analysis of coat protein genes of the 17 CMV isolates were performed in this study. The results showed that the 17 CMV isolates were identified as the members of CMV belonging to subgroupⅠB and exhibited low genetic diversity. Overall，the molecular clustering of CMV isolates from Xinjiang was not well correlated with their geographic origin. Except for Datura stramonium，there were no obvious correlations of host responses to inoculation with CMV isolates from different geographical locations. Host reaction on different hosts revealed some differences compared to the CMV isolates collected from other countries.