[Differentiated conditions for the induction of suberin synthesis or cell proliferation in potato tuber tissue after derepression].

Experiments with potato tuber fragments under normal atmospheric conditions (0.03% CO2) suggest that a wound periderm, prominently marked by suberin synthesis, develops regularly, independently of preparation technics. It has been demonstrated that potato parenchym is able to perform differentiated reactions depending on the changing influences on the reacting cells caused by the wound stimulus and partial isolation. Suberin synthesis and the cicatrization effect can be suppressed totally if changes remain insignificant as compared with the cellular state in the intact organ. This requires: 1. separating the tissue without bruising it to avoid deformations of the protoplasmatic structure; 2. removing adjacent fragments of destroyed cells by rinsing the slices; 3. maintaining cell turgidity by keeping the moisture in the reaction atmosphere at 100%. Moreover 10% CO2-concentration is necessary, corresponding to the intercellular air in situ.Whithin 24 hours after depression these conditions induce spontaneous proliferation uniformly in all superficial cell layers of tissue slices, accompanied by multiple mitosis in place of the typical suberized wound periderm. Inhibition of suberin biosynthesis is reversible by subsequent modification of reaction conditions. In contrast a method has been found to induce suberin formation only and to suppress any cell division activity (Kahl et al., 1969 a). This provides the opportunity to analyse causal corresponding physiological reactions in genetically identical cells. The advantage of this method-compared with long term experiments involving hormone-activated growth in sterile tissue culture - is the possibility of controlling quantitative and qualitative changes in biochemical pathways immediately after derepression.