Mammillaria vetula

Current name and historical gracilis

POWO accepts Mammillaria vetula Mart., published in 1832. Mammillaria gracilis Pfeiff. and M. vetula subsp. gracilis (Pfeiff.) D.R.Hunt are now synonyms. The same synonymy includes Mammillaria magneticola and the combination M. vetula subsp. magneticola. Former names remain necessary to connect studies with the current species. [2-WWW] [2-WWW]

Species range and origin of the plants studied

The native range indicated in POWO covers Mexico from Guanajuato to Veracruz, in desert and dry scrub environments. The 2023 study by Lopez-Granero and colleagues concerned material of the cultivar Snowcap from a nursery in Almería, Spain. The origin of this culture and the broad natural range of the species describe different levels of documentation. [2-WWW] [Lopez-Granero et al. 2023, Lopez-Granero et al., p. 760]

Odmiana uprawna Snowcap

The authors describe Snowcap as a form with clusters of short white spines and abundant offsets on the sides and upper part of the plant. In their description, mature clumps reach about 10–12 cm in diameter and 6–8 cm in height, sometimes up to 10 cm. Flowers are small and cream-yellow, with a pinkish or brownish central stripe. These characters concern the cultivar described. [Lopez-Granero et al. 2023, p. 760]

The current form Mammillaria vetula ‘Snowcap’ gives the species and cultivar name. The publication used the longer designation M. vetula ssp. gracilis var. Arizonica cv. Snowcap. This was retained in the article's bibliographic record, but the cultivar was not counted as another wild species or accepted subspecies. [Lopez-Granero et al. 2023, title and p. 760. POWO, as of 11 October 2026] [2-WWW] [2-WWW]

Stimulating offsets from areoles

In MS culture at 25 ± 1°C, with a sixteen-hour photoperiod and 45 µmol photons/m²/s, large explants 3–4 cm long were treated for three days with 5 mg/l GA₃. The treatment included 0.5 mg/l NAA and 0.3 mg/l kinetin according to Table 1 and the main results. After eight weeks, a mean of 34.9 ± 5.9 offsets per explant was obtained, and all explants produced offsets. Each treatment included 35 explants and three repetitions of the experiment. [Lopez-Granero et al. 2023, pp. 761–765, Tables 1 and 5]

Different medium numbering, 0.1 mg/l NAA and 30 g/l sucrose appear in the abstract, while Table 1 and the results description give 0.5 mg/l NAA and 20 g/l sucrose. This account follows the latter version, consistent between the table and results. The detailed discrepancies are also described alongside the source. [Lopez-Granero et al. 2023, p. 759, 763–765]

Rooting and acclimatisation

The rooting medium, identified as MSM-3 in Table 1, contained 5 mg/l ancymidol and 10 g/l sucrose. All shoots tested rooted in this treatment, confirmed for lengths of 1, 3 and 6 cm. The resulting plants were acclimatised with a gradual reduction in air humidity. The results report 100% survival after two months, while the methods describe a four-month procedure and assessment. [Lopez-Granero et al. 2023, p. 762–763, 766, tab. 7]

Kwitnienie in vitro

Large plants 4–6 cm long underwent preparation with reduced medium components, night temperatures of 4–6°C and changes in photoperiod. Lighting for the flowering experiments was 450 µmol photons/m²/s. Preparation alone did not lead to flower initiation. After application of 1 mg/l paclobutrazol, initiation was found in 66 ± 6% of explants, with a mean of 1.40 ± 0.16 flowers per explant. Higher doses gave a lower percentage. [Lopez-Granero et al. 2023, p. 761–762, 766–767, tab. 8]

The paper gives differing durations for preparation and assessment of flowering. Table 8 states six weeks, the methods eight, and the abstract a month of treatment followed by transfer. The result confirms the possibility of flower initiation in specific material, leaving details of the protocol timetable unresolved. [Lopez-Granero et al. 2023, pp. 759, 761–762, 766–767]

Tubercle anatomy of gracilis material

In Ozerova and Timonin's study, material identified as Mammillaria vetula subsp. gracilis had firm tubercles up to 6 mm long and 3 mm in diameter. The voucher specimen Ozerova 20-2 was deposited in the MHA herbarium. The former subspecies gracilis is a synonym of M. vetula in POWO. The results concern the anatomical material of this paper, without equating it with another cultivar studied. [Ozerova and Timonin 2020a, Ozerova and Timonin, pp. 11–12] [2-WWW]

Larger vascular bundles and a fine network of cortical bundles were found in the tubercles. Chlorenchyma filled the spaces around them, with no separately identified hydrenchyma. In the outer layer, small cells were arranged in oblique rows of four or five. The inner layer had elongated, longitudinally organised cells. The cell arrangement became clear only when longitudinal and transverse sections were compared. [Ozerova and Timonin 2020a, pp. 12–14, Fig. 2–3]

The authors describe the outer tissue as columnar chlorenchyma and relate its organisation to CO₂ supply and malate storage in vacuoles during CAM metabolism. This is an anatomical interpretation. Neither gas exchange nor CO₂ conductance was directly measured in the material discussed. [Ozerova and Timonin 2020a, pp. 14–16]

CAM in normal and altered in vitro tissues

Balen and colleagues compared potted Mammillaria vetula plants (called M. gracilis in the paper) with normal in vitro shoots, spontaneous callus, hyperhydric shoots from that callus and a tumour-tissue line induced by Agrobacterium tumefaciens. Culture was maintained without growth regulators on MS with 3% sucrose and 0.9% agar, at 24°C, with a sixteen-hour day and 90 µmol photons/m²/s. Potted plants had the same light and temperature conditions. These results come from a separate experiment on material identified as M. gracilis. [Balen et al. 2012, pp. 1884–1886. POWO, 11 October 2026] [2-WWW]

Normal in vitro shoots retained higher acidity at the end of the night than during the day, with a smaller difference than in potted plants. Callus, hyperhydric shoots and tumour tissue showed no significant daily acidity rhythm. PEPC enzyme activity was detected in all material types, with the highest value two hours after darkness began. The measurement revealed enzyme activity even in tissues without a significant nocturnal rise in acidity. CAM was assessed here using acidity, fluorescence and biochemical measurements. [Balen et al. 2012, p. 1887–1891, ryc. 2–4]

Maximum photosystem II efficiency, expressed as the fluorescence ratio Fv/Fm, averaged 0.786 in potted plants, 0.730 in normal in vitro shoots, 0.640 in callus, 0.686 in hyperhydric shoots and 0.466 in tumour tissue. Each mean was calculated from six samples, each an individual plant or flask. The index describes maximum photochemical efficiency of photosystem II under the fluorescence measurement conditions. [Balen et al. 2012, pp. 1885–1887, Table 2]

Spine micromorphology in culture

Peharec and colleagues compared spines of M. gracilis material from five-year greenhouse cultivation, normal in vitro shoots and hyperhydric shoots. Using scanning microscopy, they examined seventeen spines of each type, fifty-one in total. Mean spine lengths were 6.18 ± 0.17 mm, 2.48 ± 0.02 mm and 1.31 ± 0.02 mm, respectively. The standard error referred to the seventeen spines examined for each type. The number of plants supplying the spines was left unspecified in the paper. [Peharec et al. 2010, p. 79–84, ryc. 4]

Greenhouse spines had small protrusions of epidermal cells. Much longer, hair-like outgrowths of these cells were observed on spines from both culture types. Hyperhydric shoots were translucent and highly hydrated, with less distinct tubercles and disturbed spine arrangement. Changes in spine surface also occurred in shoots considered normal. Growth conditions and material age varied together in this comparison. [Peharec et al. 2010, p. 80–85, ryc. 1–5]

Related articles