Copiapoa humilis subsp. tenuissima

Name and material studied

The current name is Copiapoa humilis subsp. tenuissima. Older combinations include C. tenuissima and C. hypogaea subsp. tenuissima. The changed circumscription links these names to one subspecies, with the horticultural form named separately. [2-WWW]

In the experiment by Lema-Rumińska and colleagues, the material was described as C. tenuissima forma monstruosa. Plants had a very dark epidermis, white woolly areoles and no spines. These features identify the cultivated material used. The authors analysed its regeneration through somatic embryos arising from cells of the plant body. [Lema-Rumińska et al. 2013, pp. 1–2]

Somatic embryos and callus

Two regeneration pathways were studied. In direct embryogenesis, embryos developed on organised tissue. In indirect embryogenesis, callus was the starting stage. This distinction allowed comparison of the medium's effects on embryo elongation and the increase in mass of regenerating tissue. [Lema-Rumińska et al. 2013, pp. 1–3]

Abscisic acid, ABA, was added to the media. Low concentrations, up to 1 µM, promoted embryo elongation in direct embryogenesis, while 10–100 µM inhibited development and caused loss of turgor. Sucrose content was also important in regeneration through callus. Increasing its concentration was associated with more embryos and increased callus fresh mass. [Lema-Rumińska et al. 2013, pp. 3–6]

Significance for propagation

The experiment shows that a tissue's developmental stage changes its response to the same substance. Callus, a globular embryo and an elongating embryo are biologically different materials. The comparative article compares this propagation pathway with organogenesis in Blossfeldia liliputana. [Lema-Rumińska et al. 2013] [Ivannikov et al. 2022]