悉生培养微缩体系食细菌线虫提高土壤激素含量的机制

The possible mechanisms underlying improvement of soil auxin content by bacterial-feeding nematodes in a gnotobiotic microcosm experiment

研究土壤食细菌线虫与细菌的相互作用及其生态功能是土壤生态学的核心内容之一。食细菌线虫取食细菌可以促进土壤中氮素的矿化,提高氮素养分的供给,改善土壤的营养条件,从而促进植物的生长发育。土壤食细菌线虫促进植物根系生长的"养分作用机制"已得到确认,而"激素作用机制"还存在争议。从供试土壤中筛选获得一株高效产IAA细菌和两种不同cp值的食细菌线虫,通过设置简化的悉生培养系统,对这两种土著食细菌线虫与土著产IAA细菌之间的相互作用,及其对土壤中IAA含量变化的影响进行研究。结果表明:两种食细菌线虫的取食均能促进细菌数量和活性的增强,食细菌线虫与产IAA细菌相互作用也能显著增加土壤中IAA的含量;这些促进作用受到接种食细菌线虫的种类以及培养时间的影响:在培养第10天和第20天时,接种cp值为1的中杆属食细菌线虫显著增加了产IAA细菌的数量;在培养第10天和第30天时,相比较接种cp值为2的头叶属食细菌线虫,接种中杆属食细菌线虫显著提高了土壤中IAA的含量。

In recent years, the interactions between bacterial-feeding nematodes and bacteria and their ecological functions in terrestrial ecosystems have been recognized to play a crucial role in soil ecology. Many studies have found that bacterial- feeding nematodes increased soil mineralization and improved the supply of inorganic nitrogen, subsequentlystimulating plant growth. The nutrient effect of the soil bacterial-feeding nematodes on root development has been investigated in a microcosm, while the auxin effect remains controversal. An indole acetic acid （IAA） -producing bacteria and two species of bacterial -feeding nematodes were isolated, screened and identified from our experimental soil. Then, the interaction between aboriginal bacterial-feeding nematodes and IAA-producing bacteria on a study on the effect of soil IAA content was implemented in a gnotobiotic microcosm experiment. In the gnotobiotic microcosm experiment, two species of aboriginal nematodes （ Cephalobus sp. and Mesorhabditis sp. ） grazing on bacteria stimulated both the bacterial growth and activity and increased the mineral nitrogen. The interactions between IAA-producing bacteria and bacterial-feeding nematodes significantly increased soil IAA content. This increase was influenced by bacterial-feeding nematode species and incubation time. Mesorhabditis However, compared and day 30 sp. （cp 1 ） significantly stimulated the growth with Cephalobus sp. （cp 2）, Mesorhabditis sp. of the IAA-producing bacteria at day 10 and day 20. more significantly increased soil IAA content at day 10