Where does the silica found on grass and other plants come from?

Question

Grass has tiny silica "teeth" on it called phytoliths:

I have trouble understanding how can a plant possibly extract silica from soil and form anything out of it. Silicon dioxide is used for chemistry glassware and can survive nearly anything.

I found that what the plants use is actually monosilicic acid in the form of $Si(OH)_4$, but I have not been able to find how that comes to be in the soil in the first place. Clearly, silicon dioxide does not hydrate in water readily the way potassium oxide does, for example, otherwise glassware would not be a thing.

And even if I knew how does the hydrated form of the oxide form, I still do not understand how do the plants manage to dehydrate it in order to prevent it from being water soluble.

Can someone explain the whole chain from $SiO_2$ through $Si(OH)_4$ back to $SiO_2$ that can be seen in the picture above?

Answer 1

Silica $\neq$ silicon dioxide! So the chain is: silicon dioxide $\left(SiO_2\right)$ to orthosilicic/monosilicic acid $\left(Si(OH)_4\right)$, which can then polymerize to form silica particles, see image below.

The first step in the chain occurs via reaction with a basic solution (e.g. aqueous sodium hydroxide, $NaOH$). The resulting $Si(OH)_4$ is water-soluble, and thus can be taken up by organisms. Enzymes such as silicatein can then catalyzes the reaction to form silicate particles. These particles can then be deposited in specific parts of the organism. See Otzen's 2012 review in Scientifica for more information.