Silicate was applied when the seedlings were either 7 or 14 days old.
The source of additional silicon was sodium silicate (BDH, Poole, Dorset, UK; 25.5–28.5% SiO2 ) solution
Silicate was added to produce a final concentration of 3 mM, and the solu- tion pH was adjusted to 4.5 – the same pH as that of the non-silicon treatment solution.