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 are the specific sites in the plant where mitotic divisions produce new cells. Most plants grow from the tips of branches and roots where apical meristems produce new cells. As a result, in all buds, at the ends of all branch tips and on root tips, apical meristems are found.