Regeneration of Blossfeldia and Copiapoa in tissue cultures

Organogenesis and embryogenesis

Organogenesis produces organs, such as shoots and roots. Somatic embryogenesis creates embryonic structures from cells of the plant body. Both pathways may begin directly in organised tissue or proceed through callus, proliferating tissue developing from an explant. The pathway depends on the material, its condition and culture conditions. [Ivannikov et al. 2022][Lema-Rumińska et al. 2013]

The supplied publications describe Blossfeldia liliputana (in the title of the 2022 paper, B. liliputiana) and the horticultural monstrous form of Copiapoa humilis subsp. tenuissima (in the 2013 paper, C. tenuissima form monstruosa). These are two different biological materials and two separate experimental systems. [Ivannikov et al. 2022][Lema-Rumińska et al. 2013]

Blossfeldia shoots from seedling fragments

Ivannikov and colleagues established cultures from fragments of sterile seedlings. An MS-type mineral medium was supplemented with growth regulators, including the cytokinin BAP and auxin 2,4-D. In B. liliputana, new shoots regenerated after callus formation, through indirect organogenesis. [Ivannikov et al. 2022, methods and results]

Light mattered for tissue development. Callus did not develop in the treatments kept in darkness, while regenerating material was obtained under light. The authors conducted experiments at 22–26°C with a sixteen-hour photoperiod. These conditions define the laboratory culture stage. [Ivannikov et al. 2022]

Subsequent procedures included rooting or grafting the resulting shoots and acclimatisation. Each stage has a different assessment endpoint, from new shoot formation through root development to continued growth outside the vessel. The paper compared three species, so combined results require retaining this scope. [Ivannikov et al. 2022]

Somatic embryos in Copiapoa

Lema-Rumińska and colleagues compared embryo development in the horticultural monstrous form of C. humilis subsp. tenuissima. The material had a dark epidermis and white areoles, with spines absent. Globular-stage embryos and callus were studied, allowing direct and indirect embryogenesis to be followed. [Lema-Rumińska et al. 2013, pp. 1–2]

The media contained abscisic acid, ABA, at concentrations from 0 to 100 µM. For directly developing embryos, low concentrations up to 1 µM were more favourable, with elongation observed. At 10–100 µM, development was inhibited and turgor was lost. The unit µM means micromoles of a substance per litre. [Lema-Rumińska et al. 2013, pp. 2–5]

Regeneration through callus also compared sucrose concentrations of 1%, 3% and 5%. A higher sucrose proportion favoured an increase in embryo number and callus fresh mass in this system. ABA affected tissue proliferation and appearance, while its effect on the number and maturation of indirect embryos differed from the response of directly developing embryos. [Lema-Rumińska et al. 2013, pp. 4–6]

Tissue condition changes the response

Globular embryos, callus and regenerating shoots are at different stages of organisation. Their different responses to a growth regulator arise from differing developmental programmes and physiological states. Comparing these papers shows why propagation results are described separately for induction, growth, rooting and acclimatisation. [Ivannikov et al. 2022][Lema-Rumińska et al. 2013]

The monstrous forms used in the experiment are cultivated material with a particular appearance. The medium study describes their regeneration. The origin of growth abnormalities is a separate topic, discussed in the article on cristata and monstrous forms. [Lema-Rumińska et al. 2013]