Primordium

Root primordia (brown spots) as seen on the butt of a freshly cut pineapple crown intended for vegetative reproduction.

A primordium (plural: primordia), in embryology, is defined as an organ or tissue in its earliest recognizable stage of development. Cells of the primordium are called primordial cells

A primordium can be considered the simplest set of initial conditions capable of triggering growth. Within any meristem are minute primordia that resemble knobby outgrowths or ribbed inverted cones.

Primordium development in plants

Primordial development in plants is critical to the proper positioning and development of plant organs. Different primordial types like the leaf and flower primordia arise from the shoot lateral meristem. The process is intricately regulated by a set of genes that affect the positioning, growth and differentiation of the primordium.

The plant hormone auxin has also been implicated in this process, with the new primordia being initiated at the placenta where the auxin concentration is the highest. Genes like STM (shoot meristem less) and CUC (cup-shaped cotyledon) are involved in defining the borders of the newly formed primordium.

See also

• Anlage
• Morphogenesis