Аннотация:Anomalous secondary thickening of the axial organs in the Centrosperms (on the example of the Amaranthaceae Juss. 2. Evolutionary aspects)]
A review of ideas on evolutionary significance of the anomalous thickening in the Centrosperms and on causes of its origin is presented. Some reasons are presented in favour of the supposition that the evolution of the anomalous secondary thickening in the Centrosperms tended to the increasing meristematization of cambium-bearing cells which gradually turned to essential initials of the anomalous thickening meristem and to the development of direct transition of the apical meristem to the meristem of secondary growth. The trend to development of cambiumless patterns of the secondary thickening in the Centrosperms is noted. This trend is demonstrated to lead to some contradictions with the requirement of providing mechanical strength of the stem and rapid formation of the storage tissue in the roots. These contradictions are estimated as constraint which do not allow the trend noted to be realized in the Centrosperms so fully as in the monocotyledons. The anomalous secondary thickening in the centrosperms is considered to be an evolutionary advanced feature, an aromorphosis, which has promoted wide distribution of the Centrosperms in the arid and semiarid zones.