The effects of sucrose concentration, photoperiod and growth regulators on stem nodal segments of potato (Solanum tuberosum) cultivars (Lady Rosetta and Chara) were studied. Firstly, stem nodal segments were cultured on Murashige and skoog's culture media (MS) containing sucrose concentrations equal to 3, 6, 9 and 12%. The highest microtubers number (7.50 ±1.0 and 1.83±0.30 / single nodal segment for lady rosetta and Chara respectively was obtained using sucrose concentration (9%) and this is why MS culture medium augmented with 9% sucrose was used to detect the effect of light/darkness photoperiod regime (16/8, 8/16 and 0/24) on explants. The best photoperiod regime is probably 16/8 over the other regimes where the numbers of microtubers per single explant reached up 7.33±1.45 and 2.33±0.33 for Lady Rosetta and Chara, respectively. The importance of light can be understood from the result that complete and continuous darkness significantly inhibited microtuber production in both cultivars. For the third type of treatments in this study MS augmented with the best sucrose concentration (9%) and the best photoperiod regime 16/8 were fixed while the effects of thidiazuron (TDZ) /dichlorophenoxy acetic acid (2,4-D) at 1and 5 ppm (individually and/or combined) were studied. In most cases, TDZ or 2, 4-D and their combinations, induced callus formation rather than microtuberization. Calli were almost compact, nodular brownish, yellowish or greenish and the highest calli fresh weights were 2.22±0.85 and 1.25±0.64 gram for Lady rosetta and Chara respectively. However, both morphogenic responses have their own promising uses in modern plant biotechnology.