Différenciation de boutons floraux, de bourgeons végétatifs, de racines et de cal à partir de l'assise sous-épidermique des ramifications florales de Nicotiana tabacum Wisc. 38. Etude infrastructurale

Ultrastructural studies of different types of differentiation, organogenetic (formation of flower buds, vegetative buds, or roots) or nonorganogenetic (callus formation), show important modifications at the subepidermal cell level. Besides the changes showing general activation leading to the first mitosis such as an increase of the ribosomes density, a more laboured endoplasmic reticulum, and a denser nucleus located near the centre, other changes seem to be related to a particular differentiation: for the flower program, an early starch accumulation and a higher mitochondrial activity in the cells take place and for the callus program important pinocytosis phenomena occur at the plasmalemma level.