Types discussion: Autism (a developmental brain disorder characterized by impaired social interaction and communication skills, and limited range of activities and interests) is the most characteristic and best studied PDD.
A meristem is the tissue in most plants containing undifferentiated cells (meristematic cells), found in zones of the plant where growth can take place. Meristematic cells give rise to various organs of the plant and keep the plant growing.hese secondary meristems are also known as lateral meristems because they are involved in lateral growth. At the meristem summit, there is a small group of slowly dividing cells, which is commonly called the central zone.
Meristems: 1  There are 3 main types of meristematic tissue in vascular seed plants ---- apical, intercalary, & lateral meristems. 2  Apical Meristem occur at the tips of roots and shoots and are responsible for the length-wise extension of the plant body known as primary growth.