Effect of Light and Darkness on Callus Induction and Plant Regeneration of Roselle Plant Leaves (Hibiscus sabdariffa L.) Cultured on Right and Reverse Orientation

Abstract

This study aimed to obtain seedlings of the Roselle plant (Hibiscus sabdariffa L.), take leaf discs from these seedlings, and induce callus, and also test the possibility of regenerating the plant from the callus induction, root formation and finally acclimating the plants resulting from regeneration to different media (peatmoss, sand, and peatmoss + sand 1:1). A high percentage of germination rate and callus induction (100%) were obtained. The length of the hypocotyl was (10.8 cm), the number of roots (12 roots/ explant), and the length of the roots (10.0 cm) at a concentration of (1.5 mg.l^-1 ) BA, in addition to obtaining high percentages of fresh weight and dry weight of callus (36.537 g and 10.100 g), respectively, when the leaves discs were cultured right and in the dark for a period of time (15 days) in the culture medium supplemented with (1.5 mg.l^-1 ) of benzyl adenine, (4 mg.l^-1) of 2,4-D, and (0.3 mg.l^-1 ) of NAA, with the addition of (0.5 mg.l^-1) of gibberellin acid. The resulting callus was yellowy-white in color and its consistency was compact and had a very intensive as compared with the other concentrations. For plant regeneration test, the concentrations of BA (2 mg.l^-1) and NAA (0.2 mg.l-¹) gave the highest mean length of shoots (8.9 cm), number shoots (5 shoots/explant), number of leaves (13 leaves/ explant) length of roots (15 cm) and number of roots (17 roots/ explant) as compared with other concentrations. At the end it has been shown that the acclimatization process on the different cultural media, petmoss gave the best results compared to other media, and the success rate was 100%.