Opuntia megapotamica var. megapotamica

Connection with the historical name

In POWO, the name Opuntia brunneogemmia is a synonym of O. megapotamica var. megapotamica. Schlindwein and Wittmann used the first name in studies conducted in 1991–1994 and published in 1997. The described characters and results concern the populations observed then in the Guaritas region of Rio Grande do Sul. [2-WWW] [Schlindwein and Wittmann 1997]

Growth form, flower and habitat of the population studied

The plants studied had a shrubby habit, reaching about 1,5 m in height. The buds were pointed and the flowers orange. Flower length including the ovary was 75–95 mm, width 60–80 mm, and the stigma usually had 7–8 lobes. Sites included sunny rocks and shallow soils among grasses and scrub. [Schlindwein and Wittmann 1997]

The rhythm of flower opening

Flowering plants were observed from late October to February, from spring to summer in the Southern Hemisphere. A single flower was active for a total of about 6–8 hours. Flowers beginning to open in late afternoon could close in the evening and reopen the next morning. The anthers were already open when the spreading perianth allowed the first insect visits. [Schlindwein and Wittmann 1997]

Stamen movement and pollination

When touched, the stamens bent towards the style. The longer outer filaments shielded the shorter inner stamens, leaving much of the pollen in a deeper layer. Females of specialised bees could reach it by moving between the pistil and stamens. Their route favoured contact with the stigma. [Schlindwein and Wittmann 1997]

Hand pollination with the flower’s own pollen produced seeds, while cross-pollination gave a result similar to natural bee visits. Flowers kept isolated and left unmanipulated produced very few seeds. Stamen movement therefore helps make pollen available, while effective reproduction also depends on how flowers are visited and how insects move between plants. [Schlindwein and Wittmann 1997]