Progressiveness and contagiousness in plant differentiation and development

Abstract

A striking feature of ontogenetic development in plants as well as animals is its continuous and progressive character. Once differentiation has set in, the organism seems to have been launched on a precise course where one event follows the other in a strict, almost inexorable sequence, each generally leading to an increase in specialization of cells and tissues. Development and differentiation appear to possess features of self-determination and self-perpetuation, differentiation in one cell or tissue often forcing its onset in others, thus depriving them of freedom of choice between different potential courses and steering development along one progressive pathway.