Solanum nigrum L. plays an important role in anti-tumor activity. Previous studies have reported an imperfect in vitro regeneration system with unclear regeneration processes. This study firstly screened the optimal explant type for regeneration, and leaf explants were finally selected as the experimental materials. On this basis, the effects of plant growth regulator combinations and sucrose concentrations on adventitious shoot induction, shoot elongation and rooting were systematically investigated using leaf explants. The results showed that leaf explants exhibited the highest adventitious shoot induction capacity, with an induction rate of 100.00%, significantly higher than petioles (71.33%) and stem segments (51.67%). Using leaf explants, the optimal Murashige and Skoog (MS) medium for adventitious shoot induction contained 2.0 mg·L⁻¹ 6-benzyladenine (BA), 0.1 mg·L⁻¹ α-naphthaleneacetic acid (NAA), 30 g·L⁻¹ sucrose and 0.7% (w/v) agar, achieving a stable adventitious shoot induction rate of 100.00%. The optimal medium for adventitious shoot elongation was MS supplemented with 0.5 mg·L⁻¹ 6-BA, 0.1 mg·L⁻¹ NAA, 30 g·L⁻¹ sucrose and 0.7% (w/v) agar, with an average of 27.67 elongated adventitious shoots per explant. The optimal rooting medium was half-strength MS medium containing 0.1 mg·L⁻¹ NAA, 30 g·L⁻¹ sucrose and 0.7% (w/v) agar, with a rooting rate of 96.67%. This study successfully established a complete and efficient tissue culture system for S. nigrum, which will facilitate large-scale propagation of this medicinally valuable plant.

Somatic embryogenesis in plants occurs via direct or indirect routes. In indirect somatic embryogenesis, embryos initiate from callus. The detachment of these embryos from callus is a critical step for plantlet recovery. Most reviews focus only on embryo induction. This review focuses specifically on the detachment stage. We examine how programmed cell death (PCD) drives this physical release. Cell death occurs in boundary callus cells and the suspensor. It does not destroy the developing embryo proper. PCD performs three main tasks. It dissolves middle lamella pectins. It removes the temporary suspensor. And it digests doomed cells to recycle nutrients for the embryo. Key proteases such as metacaspases execute this death program, with vacuolar processing enzymes representing candidate execution proteases. Epigenetic marks and transcription factors restrict cell death to the boundary. We also discuss practical ways to regulate PCD in tissue culture.