Pharmacognosy - medicinal plants (herbs)

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Theme III.b: Micromorphological characteristics of plant drugs (vegetal drugs, herbal drugs)

Primary meristems: Protoderm, Ground meristem and procambium.

Primary meristems. Definition and characteristics. Protoderm, Ground meristem and procambium. 

Primary meristems

Are those that occur directly during development of the embryo cells, are called primary for being the first that originate and are located at the tips of stems, roots and axillary buds.

The primary meristems include three main groups of tissues:


The protoderm is formed by the peripherals cell layer and gives rise to dermal tissue.

Ground meristem

The ground meristem is formed by isodiametric cells relatively large and thin walls. This tissue gives rise to the pith, the endodermis and cortex.


The procambium is formed by smaller cells and longer than the ground meristem, gives rise to primary vascular tissue cells (primary xylem and primary phloem) and the pericycle.

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