Determination of Plant Organs and Cells
In the development of a multicellular organism there occurs a progressive loss of developmental potential in each part as it differentiates, and it is a requirement that this occur for development to proceed normally. There must be mechanisms to suppress the expression of inappropriate developmental programs in each part of the organism. Biologists studying this phenomenon in animals have come to the conclusion that the restriction of developmental potential seen at the organ level occurred also at the cellular level. The concepts that emerged from a long series of studies over many years, first in experimental embryology, then in regeneration, and most recently in studies of cultured cells, were those of competence and determination. It was demonstrated that early in development organ initials and cells had multiple developmental potential, but that at some particular time and site cells or groups of cells became “competent” to react to a specific signal that would cause them to become “determined”. Their subsequent development and differentiation was then independent of further exogenous signals. The fact that competence was site specific could be demonstrated by grafting cells from another region into a developmental site and showing that the grafted cells acquired the ability to develop in accordance with their new position, and determination could be demonstrated by removing the organ or cells to a new environment, either a new graft site or into sterile culture, where it continued to develop as it would have in the original site (1).
KeywordsShoot Apical Meristem Floral Meristem Sterile Culture Determined State Leaf Primordium
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