What is promeristem and what role does it play in plant growth?

Promeristem is the earliest, most primitive form of meristematic tissue found at the extreme tips of roots and shoots. It consists of actively dividing, self-perpetuating initial cells that give rise to all other meristematic tissues. The promeristem maintains a constant supply of undifferentiated cells while simultaneously producing derivatives that develop into primary meristems (protoderm, ground meristem, and procambium). This tissue is characterized by small, isodiametric cells with thin walls, dense cytoplasm, and prominent nuclei. The promeristem's activity ensures continuous growth and the formation of all primary tissues in plants, making it essential for plant development from embryonic stages through maturity.