Silicon Deposition in Roots and its Possible Functions

Silicon (Si) is a mysterious element in plants. It is not considered to be an essential element, but its tissue concentration can exceed that of many essential elements in some plant species and many studies show that it alleviates abiotic and biotic stresses. This occurs even in evolutionary distant species, from the most primitive to the most advanced. In the majority of these species the root takes up Si and transports it to aboveground organs. In addition, in some plant species root tissues are also sites of high Si accumulation. Three different modes of Si deposition in roots have been identified: (1) impregnation of tertiary endodermal cell walls (e.g. in cereals, such as Triticum [wheat] and Oryza [rice], and bamboos); (2) formation of Si-aggregates associated with endodermal cell walls (e.g. in the Andropogoneae family, which includes Sorghum and Saccharum [sugarcane]); (3) formation of Si aggregates in “stegmata” cells, which form a sheath around sclerenchyma fibres in some palm species (e.g. Phoenix [date palm]). In addition to differences in its location, the ratio of mineral to organic Si in roots also varies between plant species. However, despite differences in the magnitude and location of Si accumulation among plant species, phylogenetic analysis indicates high sequence homology of Si transporters. In this presentation, the various forms of Si deposition in roots will be illustrated together with relative transcript quantification of Si transporters; their functions and possible roles in stress resistance will be discussed.

Acknowledgement

The work was supported by Slovak Research and Development Agency under the Contract APVV-15-0156 and APVV SK-AT 2015-0009.