Soil-root interactions under conditions of high mechanical resistance facilitated by root mucilage secretion

Abstract

Abstract Background and Aim To investigate the independent effects of soil mechanical resistance (SMR) on the properties of two maize cultivars (703 and 704), an experiment was conducted. Methods The SMR was manipulated by inducing soil compaction at five levels, resulting in different bulk densities (1.56, 1.6, 1.66, 1.69, and 1.71 Mg.m-3), along with cementation in a loamy sand soil. These manipulations were carried out while maintaining a constant matric potential. Results The studied plants responded to the increased soil mechanical resistance (SMR) by exuding mucilage, which effectively reduced the resistance to root penetration. However, when SMR was increased through compaction, it ultimately resulted in a decrease in root water uptake, particularly at bulk densities exceeding 1.6 Mg.m-3 (equivalent to SMR > 1.8 MPa). Furthermore, the cementation treatment and the increase in SMR consistently impacted plant function and properties, resulting in a continuous decrease in plant growth. The findings revealed a significant correlation between SMR, mucilage exudation by roots, and Total Root Water Uptake (TRWU) in the treatments examined. Conclusions As this study did not identify a specific threshold value of SMR that triggered an abrupt response in plant behavior, the exudation weight and water content of root mucilage can be considered as potential criteria for determining the critical limit of SMR. Since root exuded mucilage is influenced by both soil properties and plant conditions, analyzing its properties can provide valuable insights into SMR thresholds.