Rhizoplast

In the strictest sense, the term refers specifically to a type of root (known as system II fiber) that is composed of contractile microfibrils of centrin and connects directly to the surface of the cell nucleus.

[1][2] Rhizoplasts appear as striated, fibrous roots that are attached to the basal bodies (the structures from which flagella arise) at their proximal end, and develop in the direction of the cell nucleus.

These are composed of centrin proteins that assemble in contractile bundles of microfibrils, similar to muscle fibers;[8] these are capable of contraction modulated by calcium ions.

He used the term to refer to a filamentous structure that connected the basal bodies and the cell nucleus, which he observed via light microscopy on the chloroplast-lacking alga Polytoma uvella.

However, in the second half of the century this relationship was disproven for many species via electron microscopy studies: very often they end in some other unrelated structure, such as the pyrenoid or the cell membrane.