Huntington's disease is a reces-sively inherited disorder. Pericycle is the outermost layer of the stele in the plant root. Primary growth results primarily from activity of the lateral meristems. Sieve cells have a fully functional protoplast with an active nucleus. Secondary wall is always located closer to the plasma membrane of a plant cell than the primary wall.
Root hairs are the smallest type of roots complete with a functional stele.
The boundary between the cortex and the stele is called endodermis. Branching in roots originates from meristem activity of surface buds much like branching in stems. Procambium gives rise to vascular tissue. Collenchyma cells are still alive at functional maturity - thus they can grow as the plant grows. Sclerenchyma and vessels are the only types of cells that are dead at functional maturity.