[Studies on the influence of pretreatment of the intact plant on embryonization of mature wing cells of Riella].

In regeneration the totality of processes which take place during the time interval between the isolation of cells and the first nuclear divisions is called embryonization. The influence of pretreatment of the intact plant on the length of this time interval ("Embryonalisierungszeit") was investigated. Regeneration was induced by isolating tissue fragments from the wing of Riella (Fig. 1).In tissues isolated from certain regions of plants grown in the dark the time for embryonization is always shorter than in those isolated from corresponding regions of plants grown under light-dark-cycles (Fig. 2).It is known that isolated tissue from plants grown under light-dark-cycles needs the more time for embryonization the older it is, i.e. the greater the distance between the tissue and the meristem is. An apical region of the wing was marked by a small incision into the margin of the wing (Fig. 3). After 12 days the increase in distance between the mark and the meristem was the same in plants grown in light-dark-cycles as it was in plants grown in the dark (Table 1). However, when the plants were grown in the dark and the tissue directly below this incision was isolated, the time for embryonization did not increase with increasing distance between the mark and the meristem (Table 2). This means that in the dark the cells do not age with respect to embryonization. However, the darkness does not have a generally retarding influence on ageing, since the cells at the base of the plant die in the dark as well as in the light-dark-cycle.