An efficient method for the collection of root mucilage from different plant species—A case study on the effect of mucilage on soil water repellency

Abstract

Root mucilage may play a prominent role in understanding root water uptake and, thus, there is revived interest in studying the function of root mucilage. However, mucilage research is hampered by the tedious procedures of mucilage collection. We developed a mucilage separator which utilizes low centrifugal forces (570 rpm) to separate the mucilage from seminal roots without the need of handling individual seeds or removing the germinated seeds from the tray/mesh to a centrifuge tube. For the different plant species, between 1 and 3.7 mL tray−1 of hydrated mucilage could be produced, with 6 trays being handled successively within 45 min. For Triticum aestivum, which showed a dry matter content of 0.5%, this was equivalent to 98.6 mg mucilage dry matter. The lowest total production was found for Zea mays with just 34 mg dry matter. The amounts of mucilage produced normalized to root tip agree well with literature data. The mucilage obtained by the new method was used to measure its effect on repellency of soil as this property directly relates to the phenomenon of lower rhizosphere soil water content during rewetting. It could be shown that repellency of the rhizosphere is affected by the quantity as well as by species‐dependent quality of mucilage in the rhizosphere. Among the species tested (Lupinus albus, Vicia faba, Zea mays, Triticum aestivum), the largest differences were observed between the two legumes. For Zea mays seminal root mucilage obtained with the new system was compared to mucilage of air born brace roots. The differences between these two mucilages, representing different root orders, indicate clearly that there is still a need for methods which enable the investigation of roots from older plants.

Spatial Distribution of Mucilage in the Rhizosphere Measured With Infrared Spectroscopy

“…For the calibration, maize root mucilage was extracted as described in Zickenrott et al (2016) in a slightly modified way. A mesh of stainless steel (2 mm diameter mesh size) was hanged into a plastic box 15 cm above surface of the box.…”

Xyloglucan is released by plants and promotes soil particle aggregation

“…Analyses of polysaccharide components of plant root mucilage generally reflect cell wall polysaccharides, and major components reported are pectic polysaccharides and arabinogalactan-proteins (Bacic et al, 1986;Moody et al, 1988;Knee et al, 2001;Driouich et al, 2013). However, relatively few studies have been done and precise identities of polysaccharides released by plants into soils and any role (s) they play in rhizospheres and wider soil environments remain largely unknown, although they are proposed to have roles in improving root penetration, soil properties and influencing soil microbial communities (York et al, 2016;Zickenrott et al, 2016).…”

Physics and hydraulics of the rhizosphere network

“…40% of terrestrial precipitation; Bengough, 2012) and hosts a tremendous number of microorganisms (Philippot et al, 2013), which together with the roots engineer the soil physical properties (Hallett et al, 2013). Prominent among such engineering activity is the secretion of mucilage from the root tips, which changes key physical properties of the soil solution: it adsorbs water (McCully and Boyer, 1997), it increases its viscosity and decreases its surface tension (Read and Gregory, 1997;Naveed et al, 2017), affecting also the contact angle (Moradi et al, 2012;Zickenrott et al, 2016;Benard et al, 2017). By changing these properties, mucilage brings into question well accepted paradigms, such as the fact that the soil water content should decrease towards the root surface (but it does not, as illustrated in Fig.…”