Silicon availability changes structural carbon ratio and phenol content of grasses

Abstract

Silicon is not an essential element in sensu stricto but affects the productivity of Poaceae. Recent field studies has shown the effect of silicon on cellulose and lignin content in bulk analyses of green compartments of different species, sampled before matter translocation in the course of senescence. Nevertheless, there is a gap in information about silicon availability and its effect on cellulose, lignin and phenol content in different plant tissues after nutrient resorption. In order to prove the effect of controlled silica supply on functional relevant carbon compounds Phragmites australis Trin. was grown in pot trials under three different levels of silicon surplus. After resorption of nutrients into rhizomes the content of silicon, lignin, cellulose and phenol were measured in different plant tissues. The results show that different levels of silicon surplus changed the plant cellulose, lignin and phenol content depending on plant tissue function. Cellulose content in tissues with stabilization function is reduced contrasting enhanced cellulose content in tissues without stabilization function. Furthermore, higher silicon surplus decreased the phenol content in photosynthetic active tissues and increased the phenol content in culm. Only weak silicon to lignin interaction was found. It is concluded that silicon affects the cellulose and phenol metabolism and the tradeoff between productivity and stabilization/defense. Considering these compounds as crucial factors in decay processes, silicon may be very important for the terrestrial and semi-terrestrial carbon turnover