A primordium, in
embryology, is defined as an organ or tissue in its earliest recognizable stage of development [ [http://www.medterms.com/script/main/art.asp?articlekey=33809 MedicineNet.com] ] . 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
leafand flowerprimordia arise from the shoot apical meristem. The process is intricately regulated by a set of genesthat affect the positioning, growthand differentiationof the primordium.
The plant hormone
auxinhas also been implicated in this process, with the new primordia being initiated at the site 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. [ [http://www.ncbi.nlm.nih.gov/sites/entrez?db=pubmed&uid=16271866&cmd=showdetailview&indexed=google Heisler et al, Patterns of auxin transport and gene expression during primordial development revealed by live imaging of the Arabidopsis inflorescence meristem, Current Biology, 2005, Vol. 15, pp 1899-1911] ]
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