Increased water retention in the rhizosphere allows for high phosphatase activity in drying soil
Increased water retention in the rhizosphere allows for high phosphatase activity in drying soil
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DOI：
10.1007/s11104-019-04234-3
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发表时间：
2019-08
期刊：
影响因子：
4.9
通讯作者：
M. Holz;M. Zarebanadkouki;A. Carminati;J. Hovind;A. Kaestner;M. Spohn
中科院分区：
文献类型：
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作者：
M. Holz;M. Zarebanadkouki;A. Carminati;J. Hovind;A. Kaestner;M. Spohn
背景和目的土壤干燥对几种根际过程产生负面影响，但植物根系能够通过释放粘液来缓解根际含水量的变化。我们建议，由于粘液和微生物胞外多糖在根际增强保水允许快速扩散的酶和底物，从而在附近的rootsMethodsTo评估扩散对酶活性的影响，磷酸酶活性和体积土壤含水量（VWC）之间的关系在无菌土壤中进行了量化。然后，大麦植物生长在根箱，并进行干燥周期，而VWC和磷酸酶活性监测中子照相和土壤zymograph.ResultsThe磷酸酶活性和VWC之间的关系是很好地描述了扩散模型（R2= 0.64），证明扩散的重要性酶活性。这一发现在植物实验中得到证实，其中磷酸酶活性在土壤干燥时强烈下降。根际土壤酶活性下降幅度小于非根际土壤：当土壤接近饱和时，根际土壤磷酸酶活性与非根际土壤磷酸酶活性之比为10;当土壤含水量为5%时，根际土壤磷酸酶活性与非根际土壤磷酸酶活性之比为63。磷酸酶活性与局部土壤含水量之间的关系符合扩散模型（根际：R2= 0.54，体积：R2= 0.63），强调了扩散对土壤酶活性的影响。在干旱土壤中，根际较高的持水能力维持了根周围较高的酶活性，这可能有利于植物养分的获取。
Background and aimsSoil drying negatively impacts several rhizosphere processes, but plant roots are capable of alleviating changes in rhizosphere water content by releasing mucilage. We propose that enhanced water retention in the rhizosphere due to mucilage and microbial extracellular polysaccharides allows for fast diffusion of enzymes and substrates, and thus high enzyme activity in the vicinity of roots.MethodsTo assess the effect of diffusion on enzyme activity, the relation between phosphatase activity and volumetric soil water content (VWC) was quantified in sterile soil. Then, barley plants were grown in rhizoboxes and subjected to a drying cycle, while VWC and phosphatase activity were monitored by neutron radiography and soil zymography.ResultsThe relation between phosphatase activity and VWC was well described by a diffusion model (R2= 0.64), demonstrating the importance of diffusion for enzyme activity. This finding was confirmed in the experiment with plants where phosphatase activity strongly decreased upon soil drying. Enzyme activity decreased less in the rhizosphere than in the bulk soil: the ratio between phosphatase activity in the rhizosphere and bulk soil was 10 when the soil was close to saturation and 63 when the soil contained 5% water. The relationship between phosphatase activity and local soil WC were well fitted by the diffusion model (rhizosphere: R2= 0.54, bulk: R2= 0.63), emphasizing the effect of diffusion on soil enzyme activity.ConclusionsOur results indicate that soil VWC has a significant effect on soil enzyme activity by increasing diffusion of enzymes and substrate. The higher retention of water in the rhizosphere maintains high enzyme activity around roots in drying soils, which might be beneficial for plant nutrient acquisition.