Surface tension, rheology and hydrophobicity of rhizodeposits and seed mucilage influence soil water retention and hysteresis

Naveed, Muhammad; Ahmed, Mutez Ali; Benard, Pascal; Brown, Lawrie; George, Timothy S.; Bengough, A. Glyn; Roose, Tiina; Koebernick, Nicolai; Hallett, Paul D.

doi:10.1007/s11104-019-03939-9

Cited by 63 publications

(96 citation statements)

References 51 publications

(96 reference statements)

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“…Ideally, the measurements should be performed with plant root mucilage. It has recently been shown that the physical properties of mucilage (water sorption, surface tension, and viscosity) differs among plant seedlings and chia seeds (Naveed et al, 2019). Besides being plant specific, the physical properties may additionally vary depending on the plant growth condition, soil texture, and mechanical stress.…”

Section: Discussionmentioning

confidence: 99%

“…Chia seed mucilage was shown to differ from maize ( Zea mays L.) and barley ( Hordeum vulgare L.) seedling mucilage. In particular, it is more viscous (Naveed et al, 2019). On the other hand, the physical properties of mucilage collected from plant seedlings were shown to be plant specific and concentration dependent, which makes it challenging to select a mucilage representative of mucilage across plant species.…”

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confidence: 99%

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Mucilage Facilitates Nutrient Diffusion in the Drying Rhizosphere

Zarebanadkouki

Fink

Benard

et al. 2019

Vadose Zone Journal

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Core Ideas Our aim was to test whether mucilage promotes diffusion of nutrients in dry soil. Mucilage favors transport of nutrients in drying soil and their uptake by plant. Mucilage increases the soil moisture in the rhizosphere as soil dries. Mucilage maintains the connectivity of liquid phase in the rhizosphere as soil dries. Despite detailed investigations of its distinct biochemical properties and their effects on the availability of nutrients for plants, the biophysical aspects of the rhizosphere, particularly the effect of mucilage on the transport of water and nutrients, are poorly understood. The aim of this study was to investigate the effect of mucilage on the diffusion of nutrients and consequently their transport through the rhizosphere into the plant roots. Phosphor imaging technique determined the temporospatial distribution of 137Cs in a model rhizosphere (a sandy soil mixed with chia seed (Salvia hispanica L) mucilage. The observed profiles of activities were used to estimate the diffusion coefficient of K in soils. A diffusion–convection equation was numerically solved to predict the transport of K and its uptake by a single plant root in drying soil. The results suggest that mucilage (i) keeps the rhizosphere wet and (ii) maintains the connectivity of the liquid phase in drying soil. In these ways, mucilage moderates the drop in diffusive transport. The modeling results showed that the presence of mucilage in the rhizosphere (i) prevents depletion of nutrients in soils with a low nutrient concentration in the soil solution and (ii) delays the risk of nutrient and/or salt accumulation in the vicinity of the root in soils with a high concentration nutrient and/or salt the soil solution. In conclusion, mucilage appears to mitigate the risk of nutrient deficiency and salinity stress as it enhances the diffusive transport in drying soil. In this way, mucilage may favor the transport of nutrients within the rhizosphere and their uptake by plant roots in drying soil.

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Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

Mucilage Facilitates Nutrient Diffusion in the Drying Rhizosphere

Zarebanadkouki

Fink

Benard

et al. 2019

Vadose Zone Journal

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“…The OM composition of mucilage and its spatial heterogeneity may be of importance for describing flow and transport processes ( Naveed et al., ) since mucilage provides OM components for coatings of pores formed by plant roots ( e.g ., Angst et al., ; Kögel‐Knabner , ). Decayed root channels could serve as preferential flow paths ( e.g ., Jarvis , ) and the distributed OM properties of pore walls could affect the transport of reactive solutes.…”

Section: Discussionmentioning

confidence: 99%

“…As assumed by Carvalhais et al (2011) and Ahmed et al (2015), mucilage composition may be affected by growing conditions of the plants such that the composition of the excreted mucilage may vary with time causing heterogeneity in OM composition in space. The OM composition of mucilage and its spatial heterogeneity may be of importance for describing flow and transport processes (Naveed et al, 2019) since mucilage provides OM components for coatings of pores formed by plant roots (e.g., Angst et al, 2016;Kö gel-Knabner, 2017). Decayed root channels could serve as preferential flow paths (e.g., Jarvis, 2007) and the distributed OM properties of pore walls could affect the transport of reactive solutes.…”

Section: Spatial Heterogeneity Of Mucilage Compositionmentioning

confidence: 99%

“…As for mucilage, also PGA contains a significant proportion of labile polysaccharides (Jones and Edwards, 1998) and shows some similar characteristics (Morel et al, 1987;Gessa and Deiana, 1992;Mikutta et al, 2006). However, PGA is a defined chemical component, while mucilage represents a mixture of proteins and polysaccharides, among others, that may dynamically change (Carminati and Vetterlein, 2013;Naveed et al, 2019). Amount and composition of mucilage are affected by plant type, age, and soil conditions (Jones et al, 2009;Carvalhais et al, 2011;Ahmed et al, 2015Ahmed et al, , 2018a, and may vary in its composition in a wider range than PGA.…”

Section: Introductionmentioning

confidence: 99%

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Spectroscopic characterization of mucilage (Chia seed) and polygalacturonic acid

Ellerbrock

Ahmed

Gerke

2019

J. Plant Nutr. Soil Sci.

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Polygalacturonic acid (PGA) has frequently been suggested and used as a model substance for studying mucilage properties and effects in soil. While PGA has a defined chemical structure, the composition of mucilage as natural product can vary in space and time depending on the plant and soil conditions. However, it is still unclear if PGA can be used as surrogate for original mucilage when considering soil–mucilage interactions in the rhizosphere. Here the organic matter (OM) composition of PGA was compared with that of Chia seed mucilage and small‐scale spatial distribution of OM composition in mucilage droplets was analysed using Fourier transform mid infrared spectroscopy in KBr‐transmission technique (FTIR). Selected regions of dried Chia seed mucilage droplets were analysed using micro‐ Fourier transform mid infrared spectroscopy in transflection technique (micro‐FTIR). For PGA, the FTIR spectra revealed lower C–H/C=O and higher C=O/C–O–C ratios as compared to Chia seed mucilage, indicating a relatively lower potential hydrophobicity and higher sorption capacity of the OM in PGA than OM in mucilage. The micro‐FTIR spectra revealed that the potential hydrophobicity of a single freeze‐dried mucilage droplet was higher at the tip as compared to regions located above the tip. The results suggest that the use of PGA as model substance for mucilage is limited especially when trying to imitate the sorption and wettability properties of the Chia seed mucilage OM. The spatial heterogeneity in OM composition as well as shifts in maxima of C=O and O–H bands in micro FTIR spectra of the cross sectioned mucilage droplet suggest that the composition of mucilage is changing with time. These findings may help initiating future studies on the dynamics and variability of OM composition of mucilage.

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Purification effects show seed and root mucilage's ability to respond to changing rhizosphere conditions

2023

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Mucilage, a polysaccharide‐containing hydrogel, is hypothesized to play a key role in the rhizosphere as a self‐organized system because it may vary its supramolecular structure with changes in the surrounding solution. However, there is currently limited research on how these changes are reflected in the physical properties of real mucilage. This study examines the role of solutes in maize root, wheat root, chia seed, and flax seed mucilage in relation to their physical properties. Two purification methods, dialysis and ethanol precipitation, were applied to determine the purification yield, cation content, pH, electrical conductivity, surface tension, viscosity, transverse 1H relaxation time, and contact angle after drying of mucilage before and after purification. The two seed mucilage types contain more polar polymers that are connected to larger assemblies via multivalent cation crosslinks, resulting in a denser network. This is reflected in higher viscosity and water retention ability compared to root mucilage. Seed mucilage also contains fewer surfactants, making them better wettable after drying compared to the two root mucilage types. The root mucilage types, on the other hand, contain smaller polymers or polymer assemblies and become less wettable after drying. However, wettability not only depends on the amount of surfactants but also on their mobility, as well as the strength and mesh size of the network structure. The changes in physical properties and cation composition observed after ethanol precipitation and dialysis suggest that the polymer network of seed mucilage is more stable and specialized in protecting the seeds from unfavorable environmental conditions. In contrast, root mucilage is characterized by fewer cationic interactions and its network relies more on hydrophobic interactions. This allows root mucilage to be more flexible in responding to changing environmental conditions, facilitating nutrient and water exchange between root surfaces and the rhizosphere soil.

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Surface tension, rheology and hydrophobicity of rhizodeposits and seed mucilage influence soil water retention and hysteresis

Cited by 63 publications

References 51 publications

Mucilage Facilitates Nutrient Diffusion in the Drying Rhizosphere

Mucilage Facilitates Nutrient Diffusion in the Drying Rhizosphere

Spectroscopic characterization of mucilage (Chia seed) and polygalacturonic acid

Purification effects show seed and root mucilage's ability to respond to changing rhizosphere conditions

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