The greatest stomata density of potato plantlets in vitro was under FL (56 mm−2) followed by R630B (48 mm−2) and R660B(46 mm−2), and the lowest value was observed in the R660BG treatment (Table 3). The stomata of potato plantlets in vitro in the FL treatment were elliptical in shape and small in size, while the stomata under R630BG and R660BG treatments were elliptical in shape with a narrower pore and were larger in size than under FL (Fig. 4).