Somatic embryogenesis and histological observations of Dracocephalum argunense Fisch. ex Link

Dracocephalum argunense is an important wild flower and medicinal plant. Its domestication has prompted researcher to find fast and effective propagation techniques. Somatic embryogenesis is not found but has not been used in D. argunense propagation. Somatic cells differentiate into somatic embryos and develop into complete plants, with a high propagation rate, high genetic stability and feasibility in artificial seed production. However, the somatic embryogenesis is usually affected by the regeneration system conditions. The present experiment systematically optimized the conditions affecting the regeneration of D. argunense and established a regeneration system with high efficiency. The process and features of embryogenesis were observed using paraffin sections. The results showed that the best explant was leaf, the most suitable medium for embryo induction was 1/MS +6-BA at 2.0 mg/L, the induction rate was 62.22%, and the multiplication rate 223.25%. The best rooting medium was 1/4MS+NAA at 0.5 mg/L and the rooting rate was 95.55%. The histological observation showed that the somatic embryo of D. argunense originated from a single embryonal cell and there was proembryo area in the plant tissue. All stages of development from single cell proembryo, through multicell proembryo, ball type embryo, torpedo embryo to mature somatic embryo with cotyledons could be observed in the area. The results of the present study can be used as a practical guide to researches and applications in germplasm conservation and fast propagation and domesticated seeds production of D. argunense.