Assessment of the effect of plant growth regulators on micropropagation of Senna (Cassia angustifolia Vahl.) medicinal plant

Senna (Cassia angustifolia Vahl.), known as an important medicinal plant, belongs to the Caesalpiniaceae family used in the treatment of some diseases such as skin infections, constipation, and intestinal worms. The aim of this study was to optimize the micropropagation of this plant. For this purpose, senna seeds were first disinfected and cultured in MS medium and the nodular stem parts were used as explants. The treatments were used to optimize the propagation medium supplemented with different concentrations of cytokinins, BA and Kin (0, 1, 2, and 4 mgL-1) in combination with NAA (0 and 0.25 mgL-1). After finding the best type and concentration of cytokinin for propagation (cytokinin BA), this growth regulator was tested in combination with various auxins to optimize the proliferation of the explants. In this experiment, BA was evaluated at three concentrations (0.5, 1, and 2 mgL-1), in combination with NAA, IAA, and IBA at two concentrations (0 and 0.25 mgL-1).  The propagated shoots (at least 3 cm long) were then exposed to two types of auxin NAA and IBA at different concentrations (0, 0.3, 0.6, and 0.9 mgL-1) to induce rooting. The results indicated that 1 mgL-1 BA treatment in combination with 0.25 mgL-1 NAA induced the maximum shoot proliferation (2.93 shoots per explant) and leaf number (21.6 leaves per shoot). Finally, NAA with 0.25 mg / l BA treatment at the concentration of 1 mgL-1 in combination with 0.25 mgL-1 NAA, was selected as the best treatment for the propagation of the explants. Maximum rooting induction obtained in 0.3 mgL-1 IBA treatment which was not significantly different from 0.3 mgL-1 NAA. Moreover, application of IBA at the concentration of 0.9 mgL-1 caused the higher mean values of root number and root length, so that it increased by 172.22 and 73.41% of the mentioned traits compared to the control, respectively. The results of this study can be used in micropropagation and extensive proliferation of this plant.