Primordia

A primordium in embryology, is an organ or tissue in its earliest recognizable stage of development.Cells of the primordium are called primordial cells. A primordium is the simplest set of cells capable of triggering growth of the would-be organ and the initial foundation from which an organ is able to grow. In flowering plants, a floral primordium gives rise to a flower. Although it is a frequently used term in plant biology, the word is used in describing the biology of all multicellular organisms Plants produce both leaf and flower primordia cells at the shoot apical meristem . Primordium development in plants is critical to the proper positioning and development of plant organs and cells. The process of primordium development is intricately regulated by a set of genes that affect the positioning, growth and differentiation of the primordium. Genes including STM and CUC are involved in defining the borders of the newly formed primordium. The plant hormone auxin has also been implicated in this process, with the new primordium being initiated at the placenta, where the auxin concentration is highest. There is still much to understand about the genes involved in primordium development. Leaf primordia are groups of cells that will form into new leaves. This bulging is caused by slower and less anisotropic, or directionally dependent, growth. Primordia initiation is the precursor for the start of a primordium, and typically confers new growth in plants once fully mature. At least in wheat plants, leaf primordium initiation rates increase with increasing ambient temperature, and the leaf number of some varieties decrease with increasing daylength. Auxin is a group of plant hormones, or phytohormones, that plays a key role in almost all areas of the growth and development of plants. There is a lot of current research being conducted to explain the role that it assists in the process of plant primordium.