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.
meristem. (mÄr`istÄm') , a specialized section of plant tissue characterized by cell division and growth. Much of the mature plant's growth is provided by meristems. Apical meristems found at the tips of stems and roots increase the length of these sections.n one type of lateral meristem, called cambium, or vascular cambium, the cells divide and differentiate to form the conducting tissues of the plant, i.e., the wood wood,botanically, the xylem tissue that forms the bulk of the stem of a woody plant.