The aim of this study was to assess the potential in vitro effects of activated charcoal and hinokitiol on microtuberization and growth of potato (Solanum tuberasum cv. Agria). Effect of these compounds was compared with abscisic acid, thidiazuron and paclobutrazol. The experiments were carried out in dark and light conditions. The number of microtubers induced per plantlet, microtuber dry and fresh weight, microtuber diameter and shoot fresh and dry weight were recorded at 60 days after culture initiation. Results under dark condition indicated that microtuberization occurred in all treatments except 0.1 percent of activated charcoal. On the other hand, activated charcoal significantly increased microtuber size at higher levels. Conversely, at lower concentration activated charcoal enhanced shoot growth. Hinokitiol at higher concentration (27 mg/l) increased only the size of the microtubers. However, the most microtuber numbers produced on media containing 2 mu m of thidiazuron. However, these microtubers were smaller than microtubers obtained from media containing activated charcoal. Activated charcoal at (0.1, 0.5 and 1 percent), paclobutrazol (4 mu M) and abscisic acid (1 mu M) induced microtuber formation under light condition. Orthogonal comparison indicated that dark and light conditions affected all of measured traits differently. The best condition for microtuberization and shoot growth was provided in light and then dark condition.
