explain what is promeristem,primary and secondary meristmatic tissues.

Promeristem 

• Group of cells which represent primary stages of meristematic cells. 
• They are found at the apices of embryonic shoots and roots and give rise to primary meristem.

Primary meristem 

• They originate from promeristems. 
• They are found at shoot and root apices, apex of leaves ans in intercalary parts. 
• They give rise to primary permanent tissue.

Secondary meristem

• Develop at the later stage from primary permanent tissue e.g. interfascicular cambium, cork cambium etc..
• Give rise to secondary permanent tissue.