Category: B.Sc II

A Meristem is a localized region of the cell which are dividing actively. There are various theories of the shoot apical Meristem. Apical Theory: It was proposed by Nageli. A single tetrahedral apical cell is the structural and functional unit of the cell . It controls all the growth processes of the cell. It is found in algae, bryophytes and pteridophytes. Histogen Theory: It was proposed by Hanstein. There are three Histogenic layers. Dermatogen which gives rise to epidermis. Periblem is destined to form the cortex. Pleurome forms the vascular cylinder. Tunica Corpus Theory : The peripheral zone consisting of one or more layers of regularly arranged cells is called as tunica and the cells surrounded by tunica is called as corpus. Histogenic layer theory: This theory was proposed by Dermen. There are three Histogenic layers . LI , LII and LIII layers