Strophocactus wittii

Name and distribution

The accepted name is Strophocactus wittii (K.Schum.) Britton & Rose. The 1997 biological study used Selenicereus wittii. POWO records a native range covering northern Brazil, Colombia, Ecuador, Peru and Venezuela. The detailed ecological account by Barthlott and colleagues draws, among other evidence, on observations along the Rio Negro near Manaus. [2-WWW] [Barthlott et al. 1997, POWO record 246169-2, 12 October 2026, pp. 175–177, 182–183]

Stems appressed to bark

The flattened stems described in the study were 6–14 cm wide, up to 60 cm long and 2–4 mm thick. Aerial roots arose on the side facing the tree, along the central and lateral vascular strands. Small areoles occurred along the margin at intervals of 5–8 mm and could bear up to 20 short whitish spines. Under strong light, the stems developed a reddish colour associated with betalain accumulation. [Barthlott et al. 1997, p. 178]

The stem is differentiated into a light-facing side and a side appressed to the trunk. In sections, the upper hypodermis contained substantially more chloroplasts than the lower layer. Mucilage cells were frequent, while starch occurred mainly in the central and lower parts of the stem. Approximately 12 stomata per mm² were reported on each surface. Its structure resembles a leaf, although the organ is a stem. [Barthlott et al. 1997, pp. 178–179]

CAM in a humid forest

In a greenhouse plant, the carbon isotope measurement yielded a δ¹³C value of −14.35‰. Gas exchange measurements showed net CO₂ uptake at night and daytime water vapour conductance close to zero. These results confirmed CAM, in which nocturnal carbon uptake is coupled with reduced daytime water loss. Under the relatively low light and high temperature of this experiment, the plant released CO₂ on a net basis during the day. [Barthlott et al. 1997, pp. 177, 179–181, Fig. 4]

The roots of an epiphyte have little surrounding substrate in which water could be stored between rainfall events. The authors related the significance of CAM to these short periods of water shortage. They also considered protection of photosynthesis under strong light through the use of CO₂ released within the tissues. This second explanation was proposed as a physiological hypothesis. [Barthlott et al. 1997, p. 180]

A flower lasting one night

Near Manaus, flowering was reported mainly in May. An individual flower began to open after sunset, reached full expansion about two hours later and started to close at sunrise. The detailed description gives a flower length of up to 27 cm and a width of 12.5 cm. The long tube was approximately 9 mm wide and contained nectar at its base. The tepals were white, while scales and hairlike spines occurred on the outer surface. [Barthlott et al. 1997, pp. 180–181]

Chromatographic analysis identified benzyl alcohol, benzyl benzoate and benzyl salicylate as the main floral scent compounds. Volatile emission intensified at night. The long tube, white perianth and nocturnal fragrance suggested pollination by hawkmoths with exceptionally long proboscises. The authors proposed two potential species, using the names Cocytius cruentus and Amphimoena walkeri. Pollination itself was not observed in the wild, so the identification of these insects remains a hypothesis based on floral structure. [Barthlott et al. 1997, pp. 181–182, Fig. 5]

Seeds that float on water

The ripe fruit was described as a greenish bristly berry approximately 3.5 cm long, opening through a longitudinal slit. Its relatively dry pulp contained numerous dark brown seeds measuring approximately 4 × 2 mm. In seed sections, the small curved embryo was surrounded by enlarged seed-coat cells that were dead and filled with air. When placed in water, the seeds floated on the surface. [Barthlott et al. 1997, pp. 179, 182, Fig. 3]

This structure fits the position of plants on tree trunks near the high-water mark. The authors combined seed buoyancy with field observations of plants completely submerged during high water. Older stems could climb approximately 2 m above the flood line. In this setting, water transport allows seeds to reach bark within the zone seasonally reached by the river. [Barthlott et al. 1997, pp. 182–183]

Conditions in greenhouse cultivation

The study material comprised three clones maintained in European botanic gardens. The plants grew well in a warm greenhouse at 30°C by day, 25°C at night and 80% relative humidity. They usually flowered from November to February, in contrast to plants observed near Manaus. The authors also reported failure to maintain them over a longer period under succulent-house conditions. These values describe successful cultivation in their collections, rather than experimentally established tolerance limits for the species. [Barthlott et al. 1997, pp. 176–177, 180]

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