North Wyke Research, Okehampton EX20 2SB, UK.
Rapid Commun Mass Spectrom. 2010 Mar 15;24(5):535-40. doi: 10.1002/rcm.4392.
One of the key processes that drives rhizosphere microbial activity is the exudation of soluble organic carbon (C) by plant roots. We describe an experiment designed to determine the impact of defoliation on the partitioning and movement of C in grass (Lolium perenne L.), soil and grass-sterile sand microcosms, using a (13)CO(2) pulse-labelling method. The pulse-derived (13)C in the shoots declined over time, but that of the roots remained stable throughout the experiment. There were peaks in the atom% (13)C of rhizosphere CO(2) in the first few hours after labelling probably due to root respiration, and again at around 100 h. The second peak was only seen in the soil microcosms and not in those with sterilised sand as the growth medium, indicating possible microbial activity. Incorporation of the (13)C label into the microbial biomass increased at 100 h when incorporation into replicating cells, as indicated by the amounts of the label in the microbial DNA, started to increase. These results indicate that the rhizosphere environment is conducive to bacterial growth and replication. The results also show that defoliation had no impact on the pattern of movement of (13)C from plant roots into the microbial population in the rhizosphere.
根系微生物活性的关键过程之一是植物根系分泌可溶性有机碳(C)。我们描述了一项实验,该实验旨在使用(13)CO(2)脉冲标记法确定刈割对草地(Lolium perenne L.)、土壤和无菌草地沙微宇宙中 C 的分配和迁移的影响。在实验过程中,茎中的脉冲衍生(13)C 随时间推移而下降,但根中的(13)C 保持稳定。在标记后的头几个小时内,根际 CO(2)的原子%(13)C 出现峰值,可能是由于根呼吸,在大约 100 小时时再次出现。第二个峰值仅在土壤微宇宙中可见,而在无菌沙作为生长介质的微宇宙中不可见,表明可能存在微生物活性。当以微生物 DNA 中的标记量开始增加时,指示复制细胞中(13)C 标记的掺入增加,100 小时时微生物生物量中(13)C 的掺入增加。这些结果表明,根际环境有利于细菌的生长和复制。结果还表明,刈割对(13)C 从植物根系向根际微生物种群的迁移模式没有影响。