Variable silicon accumulation in plants affects terrestrial carbon cycling by controlling lignin synthesis

Abstract

Current climate and land-use changes affect regional and global cycles of silicon (Si), with yet uncertain consequences for ecosystems. The key role of Si in marine ecology by controlling algae growth is well recognized but research on terrestrial ecosystems neglected Si since not considered an essential plant nutrient. However, grasses and various other plants accumulate large amounts of Si, and recently it has been hypothesized that incorporation of Si as a structural plant component may substitute for the energetically more expensive biosynthesis of lignin. Herein, we provide evidence supporting this hypothesis. We demonstrate that in straw of rice (Oryza sativa) deriving from a large geographic gradient across South-East Asia, the Si concentrations (ranging from 1.6% to 10.7%) are negatively related to the concentrations of carbon (31.3% to 42.5%) and lignin-derived phenols (32 to 102 mg/g carbon). Less lignin may explain results of previous studies that Si-rich straw decomposes faster. Hence, Si seems a significant but hardly recognized factor in organic carbon cycling through grasslands and other ecosystems dominated by Si-accumulating plants.

Silicon accumulation in rice plant aboveground biomass affects leaf carbon quality

“…For references of the wave numbers for the different compounds see Table 1. This relative decrease in contribution of carbohydrates is not necessarily in contradiction with the reported reduction of absolute carbohydrate concentration due to increased Si content (Schoelynck et al 2010;Schaller et al 2012a;Klotzbücher et al 2018). It was already suggested that Si accumulation leads to a decrease in cellulose, lignin and phenol concentrations in plants (Schoelynck et al 2010;Schaller et al 2012a;Klotzbücher et al 2018).…”

“…It was shown that Si content is negatively related to carbon contents in aboveground biomass of plants (Neu et al 2017;Klotzbücher et al 2018). It was also found that Si content affects the carbon quality of aboveground plant biomass.…”

“…It was also found that Si content affects the carbon quality of aboveground plant biomass. Silicon content seems to be negatively related to plant phenol content (Schaller et al 2012a), is both either increasing or decreasing plant cellulose content (Schoelynck et al 2010;Schaller et al 2012a), depending on species, and has negative or no obvious effect on plant lignin content (Schoelynck et al 2010;Schaller et al 2012a;Klotzbücher et al 2018).…”

Elevated atmospheric CO2 suppresses jasmonate and silicon‐based defences without affecting herbivores

“…Secondly, several studies have found negative correlations between silicon and total carbon, phenolics and lignin, indicating a consistent carbon–silicon trade‐off in plants (Frew, Powell, Sallam, Allsopp, & Johnson, 2016; Klotzbücher et al, 2018). The proposed mechanism for this trade‐off is that grasses can use Si as a substitute for more energetically costly carbon‐based compounds (e.g.…”

Combined effects of soil silicon and drought stress on host plant chemical and ultrastructural quality for leaf‐chewing and sap‐sucking insects

“…Hashemi, Abdolzadeh, and Sadeghipour () showed that Si prevents an increased cell wall lignification in plants under salinity stress. In addition, there is evidence for a trade‐off between carbon‐based compounds and Si‐based defences in some Si‐accumulator plants, in which Si‐treated plants may exhibit reduced carbon compounds (Cooke & Leishman, ; Frew, Powell, Sallam, Allsopp, & Johnson, ; Klotzbücher et al, ; Schaller, Brackhage, & Dudel, ). However, in relation to lignin, hemicellulose and cellulose contents, collard was not influenced by Si fertilization under different conditions of soil moisture.…”