Formation of silica aggregates in sorghum root endodermis is predetermined by cell wall architecture and development

Silicon (Si) is an element frequently associated with remedial properties in plant defence against various biotic stressors. Application of Si in plant–fungus interactions offers an intriguing research subject for its potential to reduce fungal disease‐related losses in agriculture. However, Si‐mediated changes in the plant metabolism must be first elucidated. The present microscopic study explores the effect of Si amendment on ultrastructural, cytological and anatomical aspects of the interaction between Sorghum bicolor ‘Gadambalia’ primary roots and the necrotrophic fungus Alternaria alternata. Bright‐field microscopy observations revealed that Si supplementation helped sorghum seedlings to restrict the growth of A. alternata, possibly by cell wall modifications of the root exodermis, limiting further fungal invasion. Ultrastructural analyses by transmission electron microscopy showed intense vesiculation in exodermal cells of inoculated roots. Fluorescence microscopy with suberin‐ and phenolic‐specific staining indicated a significant enhancement in the deposition of these substances in exodermal cell walls upon Si supplementation. The increased accumulation of phenolics in Si‐supplied plants was also confirmed by Raman spectroscopy. In conclusion, Si amendment seemed to alleviate the negative effect of A. alternata infection in sorghum roots, which is shown by restricted distribution of fungal hyphae in root tissues probably due to Si‐mediated deposition of suberin and phenolics in the exodermis.

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“…Spectra are presented as means and analysed using peak assignments shown in Soukup et al . () and references therein.…”

Section: Methodsmentioning

confidence: 99%

Silicon‐mediated cell wall modifications of sorghum root exodermis and suppression of invasion by fungus Alternaria alternata

et al. 2018

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“…As the metabolic costs of silica deposition were estimated to be 20-fold lesser than that of lignification (Raven, 1983), silicification can present preferable solution for improving mechanical properties of plant tissues. However, silica seems not to provide water repelling properties comparable to lignin and its utilization thus require some degree of regulation (Soukup et al, 2017). …”

Section: Sites Of Silicification In Grassesmentioning

confidence: 99%

“…Afterward, Si is transferred with the transpiration stream basipetally through the central cylinder (Lux et al, 2003b; Soukup et al, 2017). While most of the Si is transported to the shoot, some Si binds to the root endodermis with high affinity (Markovich et al, 2015).…”

Section: Sites Of Silicification In Grassesmentioning

confidence: 99%

“…This model was evidenced in sorghum, where the aerial parts of adventitious roots silicified even before reaching the growth medium (Sangster and Parry, 1976b). Accordingly, silica deposition was detected in the basal parts of roots grown with Si supply provided to their apices only (Lux et al, 2003b), even if the cortical tissues between those regions were removed (Soukup et al, 2017). …”

Section: Sites Of Silicification In Grassesmentioning

confidence: 99%

“…The aggregation sites are established even in the absence of Si, indicating that the formation of silica aggregates is at least partially controlled by the structure and composition of the endodermal cell walls (Soukup et al, 2017). The aggregates seem to swell the silicifying wall and protrude from the endodermal inner tangential wall toward the cell lumen ( Figure 1F ).…”

Section: Sites Of Silicification In Grassesmentioning

confidence: 99%

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Silicification in Grasses: Variation between Different Cell Types

2017

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Plants take up silicon as mono-silicic acid, which is released to soil by the weathering of silicate minerals. Silicic acid can be taken up by plant roots passively or actively, and later it is deposited in its polymerized form as amorphous hydrated silica. Major silica depositions in grasses occur in root endodermis, leaf epidermal cells, and outer epidermal cells of inflorescence bracts. Debates are rife about the mechanism of silica deposition, and two contrasting scenarios are often proposed to explain it. According to the passive mode of silicification, silica deposition is a result of silicic acid condensation due to dehydration, such as during transpirational loss of water from the aboveground organs. In general, silicification and transpiration are positively correlated, and continued silicification is sometimes observed after cell and tissue maturity. The other mode of silicification proposes the involvement of some biological factors, and is based on observations that silicification is not necessarily coupled with transpiration. Here, we review evidence for both mechanisms of silicification, and propose that the deposition mechanism is specific to the cell type. Considering all the cell types together, our conclusion is that grass silica deposition can be divided into three modes: spontaneous cell wall silicification, directed cell wall silicification, and directed paramural silicification in silica cells.

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Imaging Polyphenolic Compounds in Plant Tissues

Otegui

2021

Recent Advances in Polyphenol Research

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Formation of silica aggregates in sorghum root endodermis is predetermined by cell wall architecture and development

Cited by 65 publications

References 83 publications

Silicon‐mediated cell wall modifications of sorghum root exodermis and suppression of invasion by fungus Alternaria alternata

Silicon‐mediated cell wall modifications of sorghum root exodermis and suppression of invasion by fungus Alternaria alternata

Silicification in Grasses: Variation between Different Cell Types

Imaging Polyphenolic Compounds in Plant Tissues

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