In defence of the selective transport and role of silicon in plants

Coskun, Devrim; Deshmukh, Rupesh; Sonah, Humira; Menzies, J. G.; Reynolds, Olivia L.; Feng, Jian; Kronzucker, Herbert J.; Bélanger, Richard R.

doi:10.1111/nph.15764

Cited by 10 publications

(7 citation statements)

References 25 publications

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“…Despite having a disputed biochemical role, Si is considered beneficial for plant growth, including crops: Si increases abiotic stress mediation (aluminium and heavy metal toxicity, salinity) and biotic stress resistance (defence against herbivores) and improves the plants' structural stability (Cooke et al, 2016;Coskun et al, 2019b;Epstein, 1994Epstein, , 1999Epstein, , 2001Exley and Guerriero, 2019;Frew et al, 2018;Katz, 2019;Ma, 2004;Richmond and Sussman, 2003). Higher plant species form a continuous spectrum in the extent to which Si is incorporated.…”

Section: Introductionmentioning

confidence: 99%

“…In rice, a cooperative system of Si-permeable channels at both the root exodermis and endodermis (called Lsi1, low silicon 1 transporter, a thermodynamically passive transporter from the family of aquaporinlike proteins) incorporates Si, whereas a metabolically active efflux transporter (Lsi2, a putative anion-channel transporter) loads Si into the xylem (Broadley et al, 2012). The research on the identification of molecular pathways and mechanisms supplements and extends the phenomenological classification of the Si uptake, in particular where genomic data are available that disclose functional Si transporters (Coskun et al, 2019b). Even this approach, however, does not seem to be sufficient to describe the real complexity of Si uptake.…”

Section: Introductionmentioning

confidence: 99%

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Silicon uptake and isotope fractionation dynamics by crop species

et al. 2020

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Abstract. That silicon is an important element in global biogeochemical cycles is widely recognised. Recently, its relevance for global crop production has gained increasing attention in light of possible deficits in plant-available Si in soil. Silicon is beneficial for plant growth and is taken up in considerable amounts by crops like rice or wheat. However, plants differ in the way they take up silicic acid from soil solution, with some species rejecting silicic acid while others actively incorporate it. Yet because the processes governing Si uptake and regulation are not fully understood, these classifications are subject to intense debate. To gain a new perspective on the processes involved, we investigated the dependence of silicon stable isotope fractionation on silicon uptake strategy, transpiration, water use, and Si transfer efficiency. Crop plants with rejective (tomato, Solanum lycopersicum, and mustard, Sinapis alba) and active (spring wheat, Triticum aestivum) Si uptake were hydroponically grown for 6 weeks. Using inductively coupled plasma mass spectrometry, the silicon concentration and isotopic composition of the nutrient solution, the roots, and the shoots were determined. We found that measured Si uptake does not correlate with the amount of transpired water and is thus distinct from Si incorporation expected for unspecific passive uptake. We interpret this lack of correlation to indicate a highly selective Si uptake mechanism. All three species preferentially incorporated light 28Si, with a fractionation factor 1000×ln (α) of −0.33 ‰ (tomato), −0.55 ‰ (mustard), and −0.43 ‰ (wheat) between growth medium and bulk plant. Thus, even though the rates of active and passive Si root uptake differ, the physico-chemical processes governing Si uptake and stable isotope fractionation do not. We suggest that isotope fractionation during root uptake is governed by a diffusion process. In contrast, the transport of silicic acid from the roots to the shoots depends on the amount of silicon previously precipitated in the roots and the presence of active transporters in the root endodermis, facilitating Si transport into the shoots. Plants with significant biogenic silica precipitation in roots (mustard and wheat) preferentially transport silicon depleted in 28Si into their shoots. If biogenic silica is not precipitated in the roots, Si transport is dominated by a diffusion process, and hence light silicon 28Si is preferentially transported into the tomato shoots. This stable Si isotope fingerprinting of the processes that transfer biogenic silica between the roots and shoots has the potential to track Si availability and recycling in soils and to provide a monitor for efficient use of plant-available Si in agricultural production.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Silicon uptake and isotope fractionation dynamics by crop species

et al. 2020

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“…Phytoliths in L. alopecuroides may contribute physiological advantages such as enhanced drought or disease stress response, as they do in higher plants, but how or whether the physical distribution of phytoliths may be related to these kinds of functions is unknown. Indeed, the precise mechanism underlying these effects is an area of lively academic debate (Coskun et al ., 2019a,b; Exley & Guerriero, 2019; Mostofa et al ., 2021). Further research will be necessary to determine whether the phytoliths of L. alopecuroides perform these roles.…”

Section: Discussionmentioning

confidence: 99%

Evapotranspiration‐linked silica deposition in a basal tracheophyte plant (Lycopodiaceae: Lycopodiella alopecuroides): implications for the evolutionary origins of phytoliths

2023

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Summary Phytoliths, microscopic deposits of hydrated silica within plants, play a myriad of functional roles in extant tracheophytes – yet their evolutionary origins and the original selective pressures leading to their deposition remain poorly understood. To gain new insights into the ancestral condition of tracheophyte phytolith production and function, phytolith content was intensively assayed in a basal, morphologically conserved tracheophyte: the foxtail clubmoss Lycopodiella alopecuroides. Wet ashing was employed to perform phytolith extractions from every major anatomical region of L. alopecuroides. Phytolith occurrence was recorded, alongside abundance, morphometric information, and morphological descriptions. Phytoliths were recovered exclusively from the microphylls, which were apicodistally silicified into multiphytolith aggregates. Phytolith aggregates were larger and more numerous in anatomical regions engaging in greater evapotranspirational activity. The tissue distribution of L. alopecuroides phytoliths is inconsistent with the expectations of proposed adaptive hypotheses of phytolith evolutionary origin. Instead, it is hypothesized that phytoliths may have arisen incidentally in the L. alopecuroides‐like ancestral plant, polymerizing from intraplant silicon accumulations arising via bulk flow and ‘leaky’ cellular micronutrient channels. This basal, nonadaptive phytolith formation model would provide the evolutionary ‘raw material’ for later modification into the useful, adaptative, phytolith deposits seen in later‐diverging plant clades.

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“…Silicon in plants is studied as a stress-ameliorating agent. Reports encompass species from diverse plant families confronting a range of both biotic and abiotic stresses (Liang et al, 2007; Van Bockhaven et al, 2013; Coskun et al, 2019). Many of these works point to Si-generated effects on plants’ oxidative state including gene regulation, protein abundance and ROS levels (Cooke and Leishman, 2016), first suggested by (Chérif et al, 1994).…”

Section: Discussionmentioning

confidence: 99%

Hydrogen peroxide modulates lignin and silica deposits in sorghum roots

Zexer

Elbaum

2021

Preprint

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Silica aggregates in the root endodermis of grasses. Availability of Si to roots is associated with variations in the balance of reactive oxygen species (ROS) and increased resistance to drought, Striga, salt and heavy metals. In sorghum (Sorghum bicolor L.), silica aggregation is patterned in an active silicification zone (ASZ) by a special type of lignin. Since lignin polymerization is mediated by ROS, we studied the formation of root lignin and silica under varied conditions of ROS and specifically hydrogen peroxide (H2O2). Sorghum seedlings were grown hydroponically under varied Si and oxidative levels. Lignin and silica deposits in the endodermis were studied by optical, scanning electron, and Raman microscopies. Cell wall composition was quantified by thermal gravimetric analysis. Silica aggregation was catalyzed by lignin modified by carbonyls. These residues were available for silica nucleation only within 2 hours of their deposition. The endodermal H2O2 concentration regulated the intensity but not the pattern of ASZ lignin deposits. Our results imply that localized secretion of modified monolignols is necessary for patterning ASZ lignin. Fast silica aggregation may locally inhibit lignin polymerization and transiently increase H2O2 levels. Such momentary local high ROS concentrations may convey Si-induced stress tolerance in the root.

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In defence of the selective transport and role of silicon in plants

Cited by 10 publications

References 25 publications

Silicon uptake and isotope fractionation dynamics by crop species

Silicon uptake and isotope fractionation dynamics by crop species

Evapotranspiration‐linked silica deposition in a basal tracheophyte plant (Lycopodiaceae: Lycopodiella alopecuroides): implications for the evolutionary origins of phytoliths

Hydrogen peroxide modulates lignin and silica deposits in sorghum roots

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