Induction of callus and establishment of suspension culture system in Cassia mimosoides herb

The aim of this study is to determine the optimal hormone concentration and suspension culture conditions for callus induction in Cassia mimosoides herb. The leaves of aseptic seedlings were used as explants to determine the effects of various concentrations of 6-BA (6-benzylamino purine) and NAA (1-naphthaleneacetic acid) on the callus induction rate through single-factor experiments. The study examined the effect of initial suspension cell inoculation and inoculum on cell biomass. Using a hormone concentration combination of 3.0 mg L-1 BA and 1.0 mg L-1 NAA, the callus induction rate of the tender leaves of the aseptic seedlings reached 100% with good callus status. In single-factor suspension cell culture experiments, an initial inoculum of 2 g and an inoculum volume of 2 mL were most conducive to the increase in cell biomass. The content of emodin in the suspension cells and the original herb of Cassia mimosoides herb was measured by high-performance liquid chromatography (HPLC). The results indicated that at the same mass, the content of emodin in the suspension cells was 12.22-fold higher compared with that in the original herb. The results indicate that the suspension cells cultured by this method can increase the content of emodin in Cassia mimosoides herb, thus providing a more convenient and efficient method to extract emodin. The small cell clusters and single cells obtained in suspension culture can be directly used for protoplast isolation and also serve as direct receptors for genetic transformation. This provides a foundation for large-scale cell culture and the genetic transformation of Cassia mimosoides herb suspension culture.