Root- and microbial-derived mucilages affect soil structure and water transport
Root- and microbial-derived mucilages affect soil structure and water transport
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DOI：
10.1046/j.1365-2389.2000.00327.x
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发表时间：
2000-09-01
影响因子：
4.2
通讯作者：
Young, IM
中科院分区：
文献类型：
--
作者：
Czarnes, S;Hallett, PD;Young, IM
植物根和根际微生物产生的分泌物，再加上蒸散作用引起的强烈的干湿循环，刺激了土壤结构的变化。我们试图使用细菌胞外多糖(葡聚糖和黄原胶)和根粘液类似物(聚半乳糖醛酸，PGA)的实验模型，以及长达10个湿润和干燥循环来分离这两个过程。为了表征土壤结构，测定了改性土的抗拉强度、吸水率和乙醇吸水率，并制作了薄片。黄原胶和PGA提高了改性土的抗拉强度，说明它们增加了颗粒间的结合能。孔隙率随着干湿循环的增加而增加，但PGA 2g L(-1)的这种增加不如黄原胶和葡聚糖明显。这表明，PGA稳定了土壤，使其免受干湿两方面的破坏作用。PGA是唯一一种影响吸水性和排斥性的多糖，导致处理土壤的润湿速度变慢。除PGA修饰的土壤外，所有处理的吸湿和干燥都增加了土壤的吸水性，降低了土壤的排斥性。因此，PGA可以通过增加颗粒之间的结合强度和降低润湿率来稳定根际的土壤结构。
The production of exudates by plant roots and microbes in the rhizosphere, together with intense wetting and drying cycles due to evapotranspiration, stimulate changes in soil structure. We have attempted to separate these two processes using an experimental model with bacterial exopolysaccharides (dextran and xanthan) and root mucilage analogues (polygalacturonic acid, PGA), and up to 10 cycles of wetting and drying. To characterize the soil structure, tensile strength, water sorptivity and ethanol sorptivity of the amended soils were measured, and thin sections were made. Xanthan and PGA induced greater tensile strength of the amended soil, suggesting that they increased the bond energy between particles. Porosity increased with each cycle of wetting and drying, and this increase was less pronounced for the PGA 2 g l(-1) than for the xanthan and dextran. This suggests that PGA stabilized the soil against the disruptive effect caused by the wetting and drying. The PGA was the only polysaccharide that influenced water sorptivity and repellency, resulting in slower wetting of the treated soil. Wetting and drying led to an increase of the sorptivity and a decrease of the repellency for all treatments with the exception of the PGA-amended soils. The PGA may therefore stabilize the soil structure in the rhizosphere by increasing the strength of bonds between particles and decreasing the wetting rate.